Copyright © 1993 Todd R. Eigenschink
Copyright © 1993, 1994, 1995, 1996, 1997, 1998 Aubrey Jaffer
Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the author.
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| 1 The Library System | How to use and customize. | |
| 2 Scheme Syntax Extension Packages | ||
| 3 Textual Conversion Packages | ||
| 4 Mathematical Packages | ||
| 5 Database Packages | ||
| 6 Other Packages | ||
| 7 About SLIB | Install, etc. | |
| Procedure and Macro Index |
| 1.1 Feature | SLIB names. | |
| 1.2 Requesting Features | ||
| 1.3 Library Catalogs | ||
| 1.4 Catalog Compilation | ||
| 1.5 Built-in Support | ||
| 1.6 About this manual |
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SLIB denotes features by symbols. SLIB maintains a list of features supported by the Scheme session. The set of features provided by a session may change over time. Some features are properties of the Scheme implementation being used. The following features detail what sort of numbers are available from an implementation.
Other features correspond to the presence of sets of Scheme procedures or syntax (macros).
Returns #t if feature is supported by the current Scheme
session.
Informs SLIB that feature is supported. Henceforth
(provided? feature) will return #t.
(provided? 'foo) ⇒ #f (provide 'foo) (provided? 'foo) ⇒ #t
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SLIB creates and maintains a catalog mapping features to locations of files introducing procedures and syntax denoted by those features.
At the beginning of each section of this manual, there is a line like
(require 'feature).
The Scheme files comprising SLIB are cataloged so that these feature
names map to the corresponding files.
SLIB provides a form, require, which loads the files providing
the requested feature.
(provided? feature) is true,
then require just returns an unspecified value.
Subsequently (provided? feature) will return #t.
The catalog can also be queried using require:feature->path.
#t.
#f.
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At the start of a session no catalog is present, but is created with the
first catalog inquiry (such as (require 'random)). Several
sources of catalog information are combined to produce the catalog:
cd to this directory before starting the
Scheme session.
Catalog files consist of one or more association lists. In the circumstance where a feature symbol appears in more than one list, the latter list’s association is retrieved. Here are the supported formats for elements of catalog lists:
(feature . <symbol>)Redirects to the feature named <symbol>.
(feature . "<path>")Loads file <path>.
(feature source "<path>")slib:loads the Scheme source file <path>.
(feature compiled "<path>" …)slib:load-compileds the files <path> ….
The various macro styles first require the named macro package,
then just load <path> or load-and-macro-expand <path> as
appropriate for the implementation.
(feature defmacro "<path>")defmacro:loads the Scheme source file <path>.
(feature macro-by-example "<path>")defmacro:loads the Scheme source file <path>.
(feature macro "<path>")macro:loads the Scheme source file <path>.
(feature macros-that-work "<path>")macro:loads the Scheme source file <path>.
(feature syntax-case "<path>")macro:loads the Scheme source file <path>.
(feature syntactic-closures "<path>")macro:loads the Scheme source file <path>.
Here is an example of a ‘usercat’ catalog. A Program in this
directory can invoke the ‘run’ feature with (require 'run).
;;; "usercat": SLIB catalog additions for SIMSYNCH. -*-scheme-*- ( (simsynch . "../synch/simsynch.scm") (run . "../synch/run.scm") (schlep . "schlep.scm") )
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SLIB combines the catalog information which doesn’t vary per user into the file ‘slibcat’ in the implementation-vicinity. Therefore ‘slibcat’ needs change only when new software is installed or compiled. Because the actual pathnames of files can differ from installation to installation, SLIB builds a separate catalog for each implementation it is used with.
The definition of *SLIB-VERSION* in SLIB file ‘require.scm’
is checked against the catalog association of *SLIB-VERSION* to
ascertain when versions have changed. I recommend that the definition
of *SLIB-VERSION* be changed whenever the library is changed. If
multiple implementations of Scheme use SLIB, remember that recompiling
one ‘slibcat’ will fix only that implementation’s catalog.
The compilation scripts of Scheme implementations which work with SLIB
can automatically trigger catalog compilation by deleting
‘slibcat’ or by invoking a special form of require:
This will load ‘mklibcat’, which compiles and writes a new ‘slibcat’.
Another special form of require erases SLIB’s catalog, forcing it
to be reloaded the next time the catalog is queried.
Removes SLIB’s catalog information. This should be done before saving an executable image so that, when restored, its catalog will be loaded afresh.
Each file in the table below is descibed in terms of its file-system independent vicinity (see section Vicinity). The entries of a catalog in the table override those of catalogs above it in the table.
implementation-vicinity ‘slibcat’This file contains the associations for the packages comprising SLIB, the ‘implcat’ and the ‘sitecat’s. The associations in the other catalogs override those of the standard catalog.
library-vicinity ‘mklibcat.scm’creates ‘slibcat’.
library-vicinity ‘sitecat’This file contains the associations specific to an SLIB installation.
implementation-vicinity ‘implcat’This file contains the associations specific to an implementation of
Scheme. Different implementations of Scheme should have different
implementation-vicinity.
implementation-vicinity ‘mkimpcat.scm’if present, creates ‘implcat’.
implementation-vicinity ‘sitecat’This file contains the associations specific to a Scheme implementation installation.
home-vicinity ‘homecat’This file contains the associations specific to an SLIB user.
user-vicinity ‘usercat’This file contains associations effecting only those sessions whose
working directory is user-vicinity.
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The procedures described in these sections are supported by all implementations as part of the ‘*.init’ files or by ‘require.scm’.
| 1.5.1 Require | Module Management | |
| 1.5.2 Vicinity | Pathname Management | |
| 1.5.3 Configuration | Characteristics of Scheme Implementation | |
| 1.5.4 Input/Output | Things not provided by the Scheme specs. | |
| 1.5.5 Legacy | ||
| 1.5.6 System | LOADing, EVALing, ERRORing, and EXITing |
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Is a list of symbols denoting features supported in this implementation.
*features* can grow as modules are required.
*features* must be defined by all implementations
(see section Porting).
Here are features which SLIB (‘require.scm’) adds to *features* when appropriate.
For each item, (provided? 'feature) will return #t
if that feature is available, and #f if not.
Is a list of pathnames denoting files which have been loaded.
Is an association list of features (symbols) and pathnames which will
supply those features. The pathname can be either a string or a pair.
If pathname is a pair then the first element should be a macro feature
symbol, source, or compiled. The cdr of the pathname
should be either a string or a list.
In the following functions if the argument feature is not a symbol it is assumed to be a pathname.
Returns #t if feature is a member of *features* or
*modules* or if feature is supported by a file already
loaded and #f otherwise.
feature is a symbol. If (provided? feature) is true
require returns. Otherwise, if (assq feature
*catalog*) is not #f, the associated files will be loaded and
(provided? feature) will henceforth return #t. An
unspecified value is returned. If feature is not found in
*catalog*, then an error is signaled.
pathname is a string. If pathname has not already been
given as an argument to require, pathname is loaded. An
unspecified value is returned.
Assures that feature is contained in *features* if
feature is a symbol and *modules* otherwise.
Returns #t if feature is a member of *features* or
*modules* or if feature is supported by a file already
loaded. Returns a path if one was found in *catalog* under the
feature name, and #f otherwise. The path can either be a string
suitable as an argument to load or a pair as described above for
*catalog*.
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A vicinity is a descriptor for a place in the file system. Vicinities hide from the programmer the concepts of host, volume, directory, and version. Vicinities express only the concept of a file environment where a file name can be resolved to a file in a system independent manner. Vicinities can even be used on flat file systems (which have no directory structure) by having the vicinity express constraints on the file name. On most systems a vicinity would be a string. All of these procedures are file system dependent.
These procedures are provided by all implementations.
Returns the vicinity of path for use by in-vicinity.
Returns the vicinity of the currently loading Scheme code. For an
interpreter this would be the directory containing source code. For a
compiled system (with multiple files) this would be the directory where
the object or executable files are. If no file is currently loading it
the result is undefined. Warning: program-vicinity can
return incorrect values if your program escapes back into a
load.
Returns the vicinity of the shared Scheme library.
Returns the vicinity of the underlying Scheme implementation. This vicinity will likely contain startup code and messages and a compiler.
Returns the vicinity of the current directory of the user. On most systems this is ‘""’ (the empty string).
Returns the vicinity of the user’s HOME directory, the directory
which typically contains files which customize a computer environment
for a user. If scheme is running without a user (eg. a daemon) or if
this concept is meaningless for the platform, then home-vicinity
returns #f.
Returns a filename suitable for use by slib:load,
slib:load-source, slib:load-compiled,
open-input-file, open-output-file, etc. The returned
filename is filename in vicinity. in-vicinity should
allow filename to override vicinity when filename is
an absolute pathname and vicinity is equal to the value of
(user-vicinity). The behavior of in-vicinity when
filename is absolute and vicinity is not equal to the value
of (user-vicinity) is unspecified. For most systems
in-vicinity can be string-append.
Returns the vicinity of vicinity restricted to name. This
is used for large systems where names of files in subsystems could
conflict. On systems with directory structure sub-vicinity will
return a pathname of the subdirectory name of
vicinity.
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These constants and procedures describe characteristics of the Scheme and underlying operating system. They are provided by all implementations.
An integer 1 larger that the largest value which can be returned by
char->integer.
In implementations which support integers of practically unlimited size, most-positive-fixnum is a large exact integer within the range of exact integers that may result from computing the length of a list, vector, or string.
In implementations which do not support integers of practically unlimited size, most-positive-fixnum is the largest exact integer that may result from computing the length of a list, vector, or string.
The tab character.
The form-feed character.
Returns a symbol denoting the generic operating system type. For
instance, unix, vms, macos, amiga, or
ms-dos.
Displays the versions of SLIB and the underlying Scheme implementation and the name of the operating system. An unspecified value is returned.
(slib:report-version) ⇒ slib "{No value for `SLIBVERSION'}" on scm "5b1" on unix
Displays the information of (slib:report-version) followed by
almost all the information neccessary for submitting a problem report.
An unspecified value is returned.
provides a more verbose listing.
Writes the report to file ‘filename’.
(slib:report)
⇒
slib "{No value for `SLIBVERSION'}" on scm "5b1" on unix
(implementation-vicinity) is "/home/jaffer/scm/"
(library-vicinity) is "/home/jaffer/slib/"
(scheme-file-suffix) is ".scm"
loaded *features* :
trace alist qp sort
common-list-functions macro values getopt
compiled
implementation *features* :
bignum complex real rational
inexact vicinity ed getenv
tmpnam abort transcript with-file
ieee-p1178 rev4-report rev4-optional-procedures hash
object-hash delay eval dynamic-wind
multiarg-apply multiarg/and- logical defmacro
string-port source current-time record
rev3-procedures rev2-procedures sun-dl string-case
array dump char-ready? full-continuation
system
implementation *catalog* :
(i/o-extensions compiled "/home/jaffer/scm/ioext.so")
...
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These procedures are provided by all implementations.
Returns #t if the specified file exists. Otherwise, returns
#f. If the underlying implementation does not support this
feature then #f is always returned.
Deletes the file specified by filename. If filename can not
be deleted, #f is returned. Otherwise, #t is
returned.
Returns a pathname for a file which will likely not be used by any other
process. Successive calls to (tmpnam) will return different
pathnames.
Returns the current port to which diagnostic and error output is directed.
Forces any pending output on port to be delivered to the output
device and returns an unspecified value. The port argument may be
omitted, in which case it defaults to the value returned by
(current-output-port).
Returns the width of port, which defaults to
(current-output-port) if absent. If the width cannot be
determined 79 is returned.
Returns the height of port, which defaults to
(current-output-port) if absent. If the height cannot be
determined 24 is returned.
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These procedures are provided by all implementations.
identity returns its argument.
Example:
(identity 3) ⇒ 3 (identity '(foo bar)) ⇒ (foo bar) (map identity lst) ≡ (copy-list lst)
The following procedures were present in Scheme until R4RS (see Language changes in Revised(4) Scheme). They are provided by all SLIB implementations.
Derfined as #t.
Defined as #f.
Returns the last pair in the list l. Example:
(last-pair (cons 1 2))
⇒ (1 . 2)
(last-pair '(1 2))
⇒ (2)
≡ (cons 2 '())
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These procedures are provided by all implementations.
Loads a file of Scheme source code from name with the default
filename extension used in SLIB. For instance if the filename extension
used in SLIB is ‘.scm’ then (slib:load-source "foo") will
load from file ‘foo.scm’.
On implementations which support separtely loadable compiled modules, loads a file of compiled code from name with the implementation’s filename extension for compiled code appended.
Loads a file of Scheme source or compiled code from name with the appropriate suffixes appended. If both source and compiled code are present with the appropriate names then the implementation will load just one. It is up to the implementation to choose which one will be loaded.
If an implementation does not support compiled code then
slib:load will be identical to slib:load-source.
eval returns the value of obj evaluated in the current top
level environment. Eval provides a more general evaluation
facility.
filename should be a string. If filename names an existing file,
the Scheme source code expressions and definitions are read from the
file and eval called with them sequentially. The
slib:eval-load procedure does not affect the values returned by
current-input-port and current-output-port.
Outputs a warning message containing the arguments.
Outputs an error message containing the arguments, aborts evaluation of the current form and responds in a system dependent way to the error. Typical responses are to abort the program or to enter a read-eval-print loop.
Exits from the Scheme session returning status n to the system.
If n is omitted or #t, a success status is returned to the
system (if possible). If n is #f a failure is returned to
the system (if possible). If n is an integer, then n is
returned to the system (if possible). If the Scheme session cannot exit
an unspecified value is returned from slib:exit.
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scm Scheme
implementation.
(require 'feature). Include this line in your code prior to
using the package.
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| 2.1 Defmacro | Supported by all implementations | |
| 2.2 R4RS Macros | ’macro | |
| 2.3 Macro by Example | ’macro-by-example | |
| 2.4 Macros That Work | ’macros-that-work | |
| 2.5 Syntactic Closures | ’syntactic-closures | |
| 2.6 Syntax-Case Macros | ’syntax-case | |
Syntax extensions (macros) included with SLIB. Also See section Structures. | ||
|---|---|---|
| 2.7 Fluid-Let | ’fluid-let | |
| 2.8 Yasos | ’yasos, ’oop, ’collect | |
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Defmacros are supported by all implementations.
Returns a new (interned) symbol each time it is called. The symbol names are implementation-dependent
(gentemp) ⇒ scm:G0 (gentemp) ⇒ scm:G1
Returns the slib:eval of expanding all defmacros in scheme
expression e.
filename should be a string. If filename names an existing file,
the defmacro:load procedure reads Scheme source code expressions
and definitions from the file and evaluates them sequentially. These
source code expressions and definitions may contain defmacro
definitions. The macro:load procedure does not affect the values
returned by current-input-port and
current-output-port.
Returns #t if sym has been defined by defmacro,
#f otherwise.
If form is a macro call, macroexpand-1 will expand the
macro call once and return it. A form is considered to be a macro
call only if it is a cons whose car is a symbol for which a
defmacr has been defined.
macroexpand is similar to macroexpand-1, but repeatedly
expands form until it is no longer a macro call.
When encountered by defmacro:eval, defmacro:macroexpand*,
or defmacro:load defines a new macro which will henceforth be
expanded when encountered by defmacro:eval,
defmacro:macroexpand*, or defmacro:load.
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Returns the result of expanding all defmacros in scheme expression e.
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(require 'macro) is the appropriate call if you want R4RS
high-level macros but don’t care about the low level implementation. If
an SLIB R4RS macro implementation is already loaded it will be used.
Otherwise, one of the R4RS macros implemetations is loaded.
The SLIB R4RS macro implementations support the following uniform interface:
Takes an R4RS expression, macro-expands it, and returns the result of the macro expansion.
Takes an R4RS expression, macro-expands it, evals the result of the macro expansion, and returns the result of the evaluation.
filename should be a string. If filename names an existing file,
the macro:load procedure reads Scheme source code expressions and
definitions from the file and evaluates them sequentially. These source
code expressions and definitions may contain macro definitions. The
macro:load procedure does not affect the values returned by
current-input-port and current-output-port.
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A vanilla implementation of Macro by Example (Eugene Kohlbecker,
R4RS) by Dorai Sitaram, (dorai@cs.rice.edu) using defmacro.
define-syntax Macro-by-Example macros
cheaply.
....
defmacro
natively supported (most implementations)
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These macros are not referentially transparent (see Macros in Revised(4) Scheme). Lexically scoped macros (i.e., let-syntax
and letrec-syntax) are not supported. In any case, the problem
of referential transparency gains poignancy only when let-syntax
and letrec-syntax are used. So you will not be courting
large-scale disaster unless you’re using system-function names as local
variables with unintuitive bindings that the macro can’t use. However,
if you must have the full r4rs macro functionality, look to the
more featureful (but also more expensive) versions of syntax-rules
available in slib Macros That Work, Syntactic Closures, and
Syntax-Case Macros.
The keyword is an identifier, and the transformer-spec
should be an instance of syntax-rules.
The top-level syntactic environment is extended by binding the keyword to the specified transformer.
(define-syntax let*
(syntax-rules ()
((let* () body1 body2 ...)
(let () body1 body2 ...))
((let* ((name1 val1) (name2 val2) ...)
body1 body2 ...)
(let ((name1 val1))
(let* (( name2 val2) ...)
body1 body2 ...)))))
literals is a list of identifiers, and each syntax-rule should be of the form
(pattern template)
where the pattern and template are as in the grammar above.
An instance of syntax-rules produces a new macro transformer by
specifying a sequence of hygienic rewrite rules. A use of a macro whose
keyword is associated with a transformer specified by
syntax-rules is matched against the patterns contained in the
syntax-rules, beginning with the leftmost syntax-rule.
When a match is found, the macro use is trancribed hygienically
according to the template.
Each pattern begins with the keyword for the macro. This keyword is not involved in the matching and is not considered a pattern variable or literal identifier.
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Macros That Work differs from the other R4RS macro implementations in that it does not expand derived expression types to primitive expression types.
Takes an R4RS expression, macro-expands it, and returns the result of the macro expansion.
macro:eval returns the value of expression in the current
top level environment. expression can contain macro definitions.
Side effects of expression will affect the top level
environment.
filename should be a string. If filename names an existing file,
the macro:load procedure reads Scheme source code expressions and
definitions from the file and evaluates them sequentially. These source
code expressions and definitions may contain macro definitions. The
macro:load procedure does not affect the values returned by
current-input-port and current-output-port.
References:
The Revised^4 Report on the Algorithmic Language Scheme Clinger and Rees [editors]. To appear in LISP Pointers. Also available as a technical report from the University of Oregon, MIT AI Lab, and Cornell.
Macros That Work. Clinger and Rees. POPL ’91.
The supported syntax differs from the R4RS in that vectors are allowed as patterns and as templates and are not allowed as pattern or template data.
transformer spec → (syntax-rules literals rules)
rules → ()
| (rule . rules)
rule → (pattern template)
pattern → pattern_var ; a symbol not in literals
| symbol ; a symbol in literals
| ()
| (pattern . pattern)
| (ellipsis_pattern)
| #(pattern*) ; extends R4RS
| #(pattern* ellipsis_pattern) ; extends R4RS
| pattern_datum
template → pattern_var
| symbol
| ()
| (template2 . template2)
| #(template*) ; extends R4RS
| pattern_datum
template2 → template
| ellipsis_template
pattern_datum → string ; no vector
| character
| boolean
| number
ellipsis_pattern → pattern ...
ellipsis_template → template ...
pattern_var → symbol ; not in literals
literals → ()
| (symbol . literals)
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Within a pattern or template, the scope of an ellipsis (...) is
the pattern or template that appears to its left.
The rank of a pattern variable is the number of ellipses within whose scope it appears in the pattern.
The rank of a subtemplate is the number of ellipses within whose scope it appears in the template.
The template rank of an occurrence of a pattern variable within a template is the rank of that occurrence, viewed as a subtemplate.
The variables bound by a pattern are the pattern variables that appear within it.
The referenced variables of a subtemplate are the pattern variables that appear within it.
The variables opened by an ellipsis template are the referenced pattern variables whose rank is greater than the rank of the ellipsis template.
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No pattern variable appears more than once within a pattern.
For every occurrence of a pattern variable within a template, the template rank of the occurrence must be greater than or equal to the pattern variable’s rank.
Every ellipsis template must open at least one variable.
For every ellipsis template, the variables opened by an ellipsis template must all be bound to sequences of the same length.
The compiled form of a rule is
rule → (pattern template inserted)
pattern → pattern_var
| symbol
| ()
| (pattern . pattern)
| ellipsis_pattern
| #(pattern)
| pattern_datum
template → pattern_var
| symbol
| ()
| (template2 . template2)
| #(pattern)
| pattern_datum
template2 → template
| ellipsis_template
pattern_datum → string
| character
| boolean
| number
pattern_var → #(V symbol rank)
ellipsis_pattern → #(E pattern pattern_vars)
ellipsis_template → #(E template pattern_vars)
inserted → ()
| (symbol . inserted)
pattern_vars → ()
| (pattern_var . pattern_vars)
rank → exact non-negative integer
where V and E are unforgeable values.
The pattern variables associated with an ellipsis pattern are the variables bound by the pattern, and the pattern variables associated with an ellipsis template are the variables opened by the ellipsis template.
If the template contains a big chunk that contains no pattern variables or inserted identifiers, then the big chunk will be copied unnecessarily. That shouldn’t matter very often.
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Returns scheme code with the macros and derived expression types of expression expanded to primitive expression types.
macro:eval returns the value of expression in the current
top level environment. expression can contain macro definitions.
Side effects of expression will affect the top level
environment.
filename should be a string. If filename names an existing file,
the macro:load procedure reads Scheme source code expressions and
definitions from the file and evaluates them sequentially. These
source code expressions and definitions may contain macro definitions.
The macro:load procedure does not affect the values returned by
current-input-port and current-output-port.
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A Syntactic Closures Macro Facility
by Chris Hanson
9 November 1991
This document describes syntactic closures, a low-level macro facility for the Scheme programming language. The facility is an alternative to the low-level macro facility described in the Revised^4 Report on Scheme. This document is an addendum to that report.
The syntactic closures facility extends the BNF rule for transformer spec to allow a new keyword that introduces a low-level macro transformer:
transformer spec := (transformer expression)
Additionally, the following procedures are added:
make-syntactic-closure capture-syntactic-environment identifier? identifier=?
The description of the facility is divided into three parts. The first
part defines basic terminology. The second part describes how macro
transformers are defined. The third part describes the use of
identifiers, which extend the syntactic closure mechanism to be
compatible with syntax-rules.
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This section defines the concepts and data types used by the syntactic closures facility.
set! special form is also a form. Examples of
forms:
17 #t car (+ x 4) (lambda (x) x) (define pi 3.14159) if define
symbol?. Macro transformers rarely distinguish symbols from
aliases, referring to both as identifiers.
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This section describes the transformer special form and the
procedures make-syntactic-closure and
capture-syntactic-environment.
Syntax: It is an error if this syntax occurs except as a transformer spec.
Semantics: The expression is evaluated in the standard transformer
environment to yield a macro transformer as described below. This macro
transformer is bound to a macro keyword by the special form in which the
transformer expression appears (for example,
let-syntax).
A macro transformer is a procedure that takes two arguments, a
form and a syntactic environment, and returns a new form. The first
argument, the input form, is the form in which the macro keyword
occurred. The second argument, the usage environment, is the
syntactic environment in which the input form occurred. The result of
the transformer, the output form, is automatically closed in the
transformer environment, which is the syntactic environment in
which the transformer expression occurred.
For example, here is a definition of a push macro using
syntax-rules:
(define-syntax push
(syntax-rules ()
((push item list)
(set! list (cons item list)))))
Here is an equivalent definition using transformer:
(define-syntax push
(transformer
(lambda (exp env)
(let ((item
(make-syntactic-closure env '() (cadr exp)))
(list
(make-syntactic-closure env '() (caddr exp))))
`(set! ,list (cons ,item ,list))))))
In this example, the identifiers set! and cons are closed
in the transformer environment, and thus will not be affected by the
meanings of those identifiers in the usage environment
env.
Some macros may be non-hygienic by design. For example, the following
defines a loop macro that implicitly binds exit to an escape
procedure. The binding of exit is intended to capture free
references to exit in the body of the loop, so exit must
be left free when the body is closed:
(define-syntax loop
(transformer
(lambda (exp env)
(let ((body (cdr exp)))
`(call-with-current-continuation
(lambda (exit)
(let f ()
,@(map (lambda (exp)
(make-syntactic-closure env '(exit)
exp))
body)
(f))))))))
To assign meanings to the identifiers in a form, use
make-syntactic-closure to close the form in a syntactic
environment.
environment must be a syntactic environment, free-names must
be a list of identifiers, and form must be a form.
make-syntactic-closure constructs and returns a syntactic closure
of form in environment, which can be used anywhere that
form could have been used. All the identifiers used in
form, except those explicitly excepted by free-names, obtain
their meanings from environment.
Here is an example where free-names is something other than the
empty list. It is instructive to compare the use of free-names in
this example with its use in the loop example above: the examples
are similar except for the source of the identifier being left
free.
(define-syntax let1
(transformer
(lambda (exp env)
(let ((id (cadr exp))
(init (caddr exp))
(exp (cadddr exp)))
`((lambda (,id)
,(make-syntactic-closure env (list id) exp))
,(make-syntactic-closure env '() init))))))
let1 is a simplified version of let that only binds a
single identifier, and whose body consists of a single expression. When
the body expression is syntactically closed in its original syntactic
environment, the identifier that is to be bound by let1 must be
left free, so that it can be properly captured by the lambda in
the output form.
To obtain a syntactic environment other than the usage environment, use
capture-syntactic-environment.
capture-syntactic-environment returns a form that will, when
transformed, call procedure on the current syntactic environment.
procedure should compute and return a new form to be transformed,
in that same syntactic environment, in place of the form.
An example will make this clear. Suppose we wanted to define a simple
loop-until keyword equivalent to
(define-syntax loop-until
(syntax-rules ()
((loop-until id init test return step)
(letrec ((loop
(lambda (id)
(if test return (loop step)))))
(loop init)))))
The following attempt at defining loop-until has a subtle bug:
(define-syntax loop-until
(transformer
(lambda (exp env)
(let ((id (cadr exp))
(init (caddr exp))
(test (cadddr exp))
(return (cadddr (cdr exp)))
(step (cadddr (cddr exp)))
(close
(lambda (exp free)
(make-syntactic-closure env free exp))))
`(letrec ((loop
(lambda (,id)
(if ,(close test (list id))
,(close return (list id))
(loop ,(close step (list id)))))))
(loop ,(close init '())))))))
This definition appears to take all of the proper precautions to prevent
unintended captures. It carefully closes the subexpressions in their
original syntactic environment and it leaves the id identifier
free in the test, return, and step expressions, so
that it will be captured by the binding introduced by the lambda
expression. Unfortunately it uses the identifiers if and
loop within that lambda expression, so if the user of
loop-until just happens to use, say, if for the
identifier, it will be inadvertently captured.
The syntactic environment that if and loop want to be
exposed to is the one just outside the lambda expression: before
the user’s identifier is added to the syntactic environment, but after
the identifier loop has been added.
capture-syntactic-environment captures exactly that environment
as follows:
(define-syntax loop-until
(transformer
(lambda (exp env)
(let ((id (cadr exp))
(init (caddr exp))
(test (cadddr exp))
(return (cadddr (cdr exp)))
(step (cadddr (cddr exp)))
(close
(lambda (exp free)
(make-syntactic-closure env free exp))))
`(letrec ((loop
,(capture-syntactic-environment
(lambda (env)
`(lambda (,id)
(,(make-syntactic-closure env '() `if)
,(close test (list id))
,(close return (list id))
(,(make-syntactic-closure env '()
`loop)
,(close step (list id)))))))))
(loop ,(close init '())))))))
In this case, having captured the desired syntactic environment, it is
convenient to construct syntactic closures of the identifiers if
and the loop and use them in the body of the
lambda.
A common use of capture-syntactic-environment is to get the
transformer environment of a macro transformer:
(transformer
(lambda (exp env)
(capture-syntactic-environment
(lambda (transformer-env)
...))))
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This section describes the procedures that create and manipulate
identifiers. Previous syntactic closure proposals did not have an
identifier data type – they just used symbols. The identifier data
type extends the syntactic closures facility to be compatible with the
high-level syntax-rules facility.
As discussed earlier, an identifier is either a symbol or an alias. An alias is implemented as a syntactic closure whose form is an identifier:
(make-syntactic-closure env '() 'a) ⇒ an alias
Aliases are implemented as syntactic closures because they behave just
like syntactic closures most of the time. The difference is that an
alias may be bound to a new value (for example by lambda or
let-syntax); other syntactic closures may not be used this way.
If an alias is bound, then within the scope of that binding it is looked
up in the syntactic environment just like any other identifier.
Aliases are used in the implementation of the high-level facility
syntax-rules. A macro transformer created by syntax-rules
uses a template to generate its output form, substituting subforms of
the input form into the template. In a syntactic closures
implementation, all of the symbols in the template are replaced by
aliases closed in the transformer environment, while the output form
itself is closed in the usage environment. This guarantees that the
macro transformation is hygienic, without requiring the transformer to
know the syntactic roles of the substituted input subforms.
Returns #t if object is an identifier, otherwise returns
#f. Examples:
(identifier? 'a) ⇒ #t (identifier? (make-syntactic-closure env '() 'a)) ⇒ #t (identifier? "a") ⇒ #f (identifier? #\a) ⇒ #f (identifier? 97) ⇒ #f (identifier? #f) ⇒ #f (identifier? '(a)) ⇒ #f (identifier? '#(a)) ⇒ #f
The predicate eq? is used to determine if two identifers are
“the same”. Thus eq? can be used to compare identifiers
exactly as it would be used to compare symbols. Often, though, it is
useful to know whether two identifiers “mean the same thing”. For
example, the cond macro uses the symbol else to identify
the final clause in the conditional. A macro transformer for
cond cannot just look for the symbol else, because the
cond form might be the output of another macro transformer that
replaced the symbol else with an alias. Instead the transformer
must look for an identifier that “means the same thing” in the usage
environment as the symbol else means in the transformer
environment.
environment1 and environment2 must be syntactic
environments, and identifier1 and identifier2 must be
identifiers. identifier=? returns #t if the meaning of
identifier1 in environment1 is the same as that of
identifier2 in environment2, otherwise it returns #f.
Examples:
(let-syntax
((foo
(transformer
(lambda (form env)
(capture-syntactic-environment
(lambda (transformer-env)
(identifier=? transformer-env 'x env 'x)))))))
(list (foo)
(let ((x 3))
(foo))))
⇒ (#t #f)
(let-syntax ((bar foo))
(let-syntax
((foo
(transformer
(lambda (form env)
(capture-syntactic-environment
(lambda (transformer-env)
(identifier=? transformer-env 'foo
env (cadr form))))))))
(list (foo foo)
(foobar))))
⇒ (#f #t)
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The syntactic closures facility was invented by Alan Bawden and Jonathan
Rees. The use of aliases to implement syntax-rules was invented
by Alan Bawden (who prefers to call them synthetic names). Much
of this proposal is derived from an earlier proposal by Alan
Bawden.
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Returns scheme code with the macros and derived expression types of expression expanded to primitive expression types.
macro:eval returns the value of expression in the current
top level environment. expression can contain macro definitions.
Side effects of expression will affect the top level
environment.
filename should be a string. If filename names an existing file,
the macro:load procedure reads Scheme source code expressions and
definitions from the file and evaluates them sequentially. These
source code expressions and definitions may contain macro definitions.
The macro:load procedure does not affect the values returned by
current-input-port and current-output-port.
This is version 2.1 of syntax-case, the low-level macro facility
proposed and implemented by Robert Hieb and R. Kent Dybvig.
This version is further adapted by Harald Hanche-Olsen <hanche@imf.unit.no> to make it compatible with, and easily usable with, SLIB. Mainly, these adaptations consisted of:
If you wish, you can see exactly what changes were done by reading the shell script in the file ‘syncase.sh’.
The two PostScript files were omitted in order to not burden the SLIB
distribution with them. If you do intend to use syntax-case,
however, you should get these files and print them out on a PostScript
printer. They are available with the original syntax-case
distribution by anonymous FTP in
‘cs.indiana.edu:/pub/scheme/syntax-case’.
In order to use syntax-case from an interactive top level, execute:
See the section Repl (See section Repl) for more information.
To check operation of syntax-case get ‘cs.indiana.edu:/pub/scheme/syntax-case’, and type
Beware that syntax-case takes a long time to load – about 20s on
a SPARCstation SLC (with SCM) and about 90s on a Macintosh SE/30 (with
Gambit).
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All R4RS syntactic forms are defined, including delay. Along
with delay are simple definitions for make-promise (into
which delay expressions expand) and force.
syntax-rules and with-syntax (described in TR356)
are defined.
syntax-case is actually defined as a macro that expands into
calls to the procedure syntax-dispatch and the core form
syntax-lambda; do not redefine these names.
Several other top-level bindings not documented in TR356 are created:
build- procedures in ‘output.ss’
expand-syntax (the expander)
The syntax of define has been extended to allow (define id),
which assigns id to some unspecified value.
We have attempted to maintain R4RS compatibility where possible. The incompatibilities should be confined to ‘hooks.ss’. Please let us know if there is some incompatibility that is not flagged as such.
Send bug reports, comments, suggestions, and questions to Kent Dybvig (dyb@iuvax.cs.indiana.edu).
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Included with the syntax-case files was ‘structure.scm’
which defines a macro define-structure. There is no
documentation for this macro and it is not used by any code in SLIB.
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(bindings …) forms…(fluid-let ((variable init) …) expression expression …)
The inits are evaluated in the current environment (in some unspecified order), the current values of the variables are saved, the results are assigned to the variables, the expressions are evaluated sequentially in the current environment, the variables are restored to their original values, and the value of the last expression is returned.
The syntax of this special form is similar to that of let, but
fluid-let temporarily rebinds existing variables. Unlike
let, fluid-let creates no new bindings; instead it
assigns the values of each init to the binding (determined
by the rules of lexical scoping) of its corresponding
variable.
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(require 'oop) or (require 'yasos)
‘Yet Another Scheme Object System’ is a simple object system for Scheme based on the paper by Norman Adams and Jonathan Rees: Object Oriented Programming in Scheme, Proceedings of the 1988 ACM Conference on LISP and Functional Programming, July 1988 [ACM #552880].
Another reference is:
Ken Dickey. <A HREF="ftp://ftp.cs.indiana.edu/pub/scheme-repository/doc/pubs/swob.txt"> Scheming with Objects </A> AI Expert Volume 7, Number 10 (October 1992), pp. 24-33.
| 2.8.1 Terms | Definitions and disclaimer. | |
| 2.8.2 Interface | The Yasos macros and procedures. | |
| 2.8.3 Setters | Dylan-like setters in Yasos. | |
| 2.8.4 Examples | Usage of Yasos and setters. |
| [ << ] | [ < ] | [ Up ] | [ > ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Any Scheme data object.
An instance of the OO system; an object.
A method.
The object system supports multiple inheritance. An instance can
inherit from 0 or more ancestors. In the case of multiple inherited
operations with the same identity, the operation used is that from the
first ancestor which contains it (in the ancestor let). An
operation may be applied to any Scheme data object—not just instances.
As code which creates instances is just code, there are no classes
and no meta-anything. Method dispatch is by a procedure call a la
CLOS rather than by send syntax a la Smalltalk.
There are a number of optimizations which can be made. This implementation is expository (although performance should be quite reasonable). See the L&FP paper for some suggestions.
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(opname self arg …) default-bodyDefines a default behavior for data objects which don’t handle the operation opname. The default behavior (for an empty default-body) is to generate an error.
Defines a predicate opname?, usually used for determining the
type of an object, such that (opname? object)
returns #t if object has an operation opname? and
#f otherwise.
((name self arg …) body) …Returns an object (an instance of the object system) with operations.
Invoking (name object arg … executes the
body of the object with self bound to object and
with argument(s) arg….
((ancestor1 init1) …) operation …A let-like form of object for multiple inheritance. It
returns an object inheriting the behaviour of ancestor1 etc. An
operation will be invoked in an ancestor if the object itself does not
provide such a method. In the case of multiple inherited operations
with the same identity, the operation used is the one found in the first
ancestor in the ancestor list.
Used in an operation definition (of self) to invoke the operation in an ancestor component but maintain the object’s identity. Also known as “send-to-super”.
A default print operation is provided which is just (format
port obj) (See section Format (version 3.0)) for non-instances and prints
obj preceded by ‘#<INSTANCE>’ for instances.
The default method returns the number of elements in obj if it is
a vector, string or list, 2 for a pair, 1 for a character
and by default id an error otherwise. Objects such as collections
(See section Collections) may override the default in an obvious way.
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Setters implement generalized locations for objects
associated with some sort of mutable state. A getter operation
retrieves a value from a generalized location and the corresponding
setter operation stores a value into the location. Only the getter is
named – the setter is specified by a procedure call as below. (Dylan
uses special syntax.) Typically, but not necessarily, getters are
access operations to extract values from Yasos objects (See section Yasos).
Several setters are predefined, corresponding to getters car,
cdr, string-ref and vector-ref e.g., (setter
car) is equivalent to set-car!.
This implementation of setters is similar to that in Dylan(TM)
(Dylan: An object-oriented dynamic language, Apple Computer
Eastern Research and Technology). Common LISP provides similar
facilities through setf.
Returns the setter for the procedure getter. E.g., since
string-ref is the getter corresponding to a setter which is
actually string-set!:
(define foo "foo") ((setter string-ref) foo 0 #\F) ; set element 0 of foo foo ⇒ "Foo"
If place is a variable name, set is equivalent to
set!. Otherwise, place must have the form of a procedure
call, where the procedure name refers to a getter and the call indicates
an accessible generalized location, i.e., the call would return a value.
The return value of set is usually unspecified unless used with a
setter whose definition guarantees to return a useful value.
(set (string-ref foo 2) #\O) ; generalized location with getter foo ⇒ "FoO" (set foo "foo") ; like set! foo ⇒ "foo"
Add procedures getter and setter to the (inaccessible) list of valid setter/getter pairs. setter implements the store operation corresponding to the getter access operation for the relevant state. The return value is unspecified.
Removes the setter corresponding to the specified getter from the list of valid setters. The return value is unspecified.
Shorthand for a Yasos define-operation defining an operation
getter-name that objects may support to return the value of some
mutable state. The default operation is to signal an error. The return
value is unspecified.
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;;; These definitions for PRINT and SIZE are
;;; already supplied by
(require 'yasos)
(define-operation (print obj port)
(format port
(if (instance? obj) "#<instance>" "~s")
obj))
(define-operation (size obj)
(cond
((vector? obj) (vector-length obj))
((list? obj) (length obj))
((pair? obj) 2)
((string? obj) (string-length obj))
((char? obj) 1)
(else
(error "Operation not supported: size" obj))))
(define-predicate cell?)
(define-operation (fetch obj))
(define-operation (store! obj newValue))
(define (make-cell value)
(object
((cell? self) #t)
((fetch self) value)
((store! self newValue)
(set! value newValue)
newValue)
((size self) 1)
((print self port)
(format port "#<Cell: ~s>" (fetch self)))))
(define-operation (discard obj value)
(format #t "Discarding ~s~%" value))
(define (make-filtered-cell value filter)
(object-with-ancestors
((cell (make-cell value)))
((store! self newValue)
(if (filter newValue)
(store! cell newValue)
(discard self newValue)))))
(define-predicate array?)
(define-operation (array-ref array index))
(define-operation (array-set! array index value))
(define (make-array num-slots)
(let ((anArray (make-vector num-slots)))
(object
((array? self) #t)
((size self) num-slots)
((array-ref self index)
(vector-ref anArray index))
((array-set! self index newValue)
(vector-set! anArray index newValue))
((print self port)
(format port "#<Array ~s>" (size self))))))
(define-operation (position obj))
(define-operation (discarded-value obj))
(define (make-cell-with-history value filter size)
(let ((pos 0) (most-recent-discard #f))
(object-with-ancestors
((cell (make-filtered-call value filter))
(sequence (make-array size)))
((array? self) #f)
((position self) pos)
((store! self newValue)
(operate-as cell store! self newValue)
(array-set! self pos newValue)
(set! pos (+ pos 1)))
((discard self value)
(set! most-recent-discard value))
((discarded-value self) most-recent-discard)
((print self port)
(format port "#<Cell-with-history ~s>"
(fetch self))))))
(define-access-operation fetch)
(add-setter fetch store!)
(define foo (make-cell 1))
(print foo #f)
⇒ "#<Cell: 1>"
(set (fetch foo) 2)
⇒
(print foo #f)
⇒ "#<Cell: 2>"
(fetch foo)
⇒ 2
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| 3.1 Precedence Parsing | ||
| 3.2 Format (version 3.0) | Common-Lisp Format | |
| 3.3 Standard Formatted I/O | Posix printf and scanf | |
| 3.4 Program and Arguments | ||
| 3.5 HTML Forms | Generate pages and serve WWW sites | |
| 3.6 Printing Scheme | Nicely | |
| 3.7 Time and Date | ||
| 3.8 Vector Graphics | ||
| 3.9 Schmooz | Documentation markup for Scheme programs |
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(require 'precedence-parse) or (require 'parse)
This package implements:
| 3.1.1 Precedence Parsing Overview | ||
| 3.1.2 Ruleset Definition and Use | ||
| 3.1.3 Token definition | ||
| 3.1.4 Nud and Led Definition | ||
| 3.1.5 Grammar Rule Definition |
| [ << ] | [ < ] | [ Up ] | [ > ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This package offers improvements over previous parsers.
? is substituted for
missing input.
Here are the higher-level syntax types and an example of each. Precedence considerations are omitted for clarity. See section Grammar Rule Definition for full details.
bye
calls the function exit with no arguments.
- 42
Calls the function negate with the argument 42.
x - y
Calls the function difference with arguments x and y.
x + y + z
Calls the function sum with arguments x, y, and
y.
5 !
Calls the function factorial with the argument 5.
set foo bar
Calls the function set! with the arguments foo and
bar.
/* almost any text here */
Ignores the comment delimited by /* and */.
{0, 1, 2}
Calls the function list with the arguments 0, 1,
and 2.
f(x, y)
Calls the function funcall with the arguments f, x,
and y.
set foo bar;
delimits the extent of the restfix operator set.
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A grammar is built by one or more calls to prec:define-grammar.
The rules are appended to *syn-defs*. The value of
*syn-defs* is the grammar suitable for passing as an argument to
prec:parse.
Is a nearly empty grammar with whitespace characters set to group 0,
which means they will not be made into tokens. Most rulesets will want
to start with *syn-ignore-whitespace*
In order to start defining a grammar, either
(set! *syn-defs* '())
or
(set! *syn-defs* *syn-ignore-whitespace*)
Appends rule1 … to *syn-defs*.
prec:define-grammar is used to define both the character classes
and rules for tokens.
Once your grammar is defined, save the value of *syn-defs* in a
variable (for use when calling prec:parse).
(define my-ruleset *syn-defs*)
The ruleset argument must be a list of rules as constructed by
prec:define-grammar and extracted from *syn-defs*.
The token delim may be a character, symbol, or string. A character delim argument will match only a character token; i.e. a character for which no token-group is assigned. A symbols or string will match only a token string; i.e. a token resulting from a token group.
prec:parse reads a ruleset grammar expression delimited
by delim from the given input port. prec:parse
returns the next object parsable from the given input port,
updating port to point to the first character past the end of the
external representation of the object.
If an end of file is encountered in the input before any characters are
found that can begin an object, then an end of file object is returned.
If a delimiter (such as delim) is found before any characters are
found that can begin an object, then #f is returned.
The port argument may be omitted, in which case it defaults to the
value returned by current-input-port. It is an error to parse
from a closed port.
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The argument chars may be a single character, a list of
characters, or a string. Each character in chars is treated as
though tok:char-group was called with that character alone.
The argument chars-proc must be a procedure of one argument, a
list of characters. After tokenize has finished
accumulating the characters for a token, it calls chars-proc with
the list of characters. The value returned is the token which
tokenize returns.
The argument group may be an exact integer or a procedure of one
character argument. The following discussion concerns the treatment
which the tokenizing routine, tokenize, will accord to characters
on the basis of their groups.
When group is a non-zero integer, characters whose group number is equal to or exactly one less than group will continue to accumulate. Any other character causes the accumulation to stop (until a new token is to be read).
The group of zero is special. These characters are ignored when parsed pending a token, and stop the accumulation of token characters when the accumulation has already begun. Whitespace characters are usually put in group 0.
If group is a procedure, then, when triggerd by the occurence of an initial (no accumulation) chars character, this procedure will be repeatedly called with each successive character from the input stream until the group procedure returns a non-false value.
The following convenient constants are provided for use with
tok:char-group.
Is the string "0123456789".
Is the string consisting of all upper-case letters ("ABCDEFGHIJKLMNOPQRSTUVWXYZ").
Is the string consisting of all lower-case letters ("abcdefghijklmnopqrstuvwxyz").
Is the string consisting of all characters between 0 and 255 for which
char-whitespace? returns true.
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This section describes advanced features. You can skip this section on first reading.
The Null Denotation (or nud) of a token is the procedure and arguments applying for that token when Left, an unclaimed parsed expression is not extant.
The Left Denotation (or led) of a token is the procedure, arguments, and lbp applying for that token when there is a Left, an unclaimed parsed expression.
In his paper,
Pratt, V. R. Top Down Operator Precendence. SIGACT/SIGPLAN Symposium on Principles of Programming Languages, Boston, 1973, pages 41-51
the left binding power (or lbp) was an independent property of tokens. I think this was done in order to allow tokens with NUDs but not LEDs to also be used as delimiters, which was a problem for statically defined syntaxes. It turns out that dynamically binding NUDs and LEDs allows them independence.
For the rule-defining procedures that follow, the variable tk may be a character, string, or symbol, or a list composed of characters, strings, and symbols. Each element of tk is treated as though the procedure were called for each element.
Character tk arguments will match only character tokens; i.e. characters for which no token-group is assigned. Symbols and strings will both match token strings; i.e. tokens resulting from token groups.
Returns a rule specifying that sop be called when tk is
parsed. If sop is a procedure, it is called with tk and
arg1 … as its arguments; the resulting value is incorporated
into the expression being built. Otherwise, (list sop
arg1 …) is incorporated.
If no NUD has been defined for a token; then if that token is a string, it is converted to a symbol and returned; if not a string, the token is returned.
Returns a rule specifying that sop be called when tk is parsed and left has an unclaimed parsed expression. If sop is a procedure, it is called with left, tk, and arg1 … as its arguments; the resulting value is incorporated into the expression being built. Otherwise, left is incorporated.
If no LED has been defined for a token, and left is set, the parser issues a warning.
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Here are procedures for defining rules for the syntax types introduced in Precedence Parsing Overview.
For the rule-defining procedures that follow, the variable tk may be a character, string, or symbol, or a list composed of characters, strings, and symbols. Each element of tk is treated as though the procedure were called for each element.
For procedures prec:delim, …, prec:prestfix, if the sop
argument is #f, then the token which triggered this rule is
converted to a symbol and returned. A false sop argument to the
procedures prec:commentfix, prec:matchfix, or prec:inmatchfix has a
different meaning.
Character tk arguments will match only character tokens; i.e. characters for which no token-group is assigned. Symbols and strings will both match token strings; i.e. tokens resulting from token groups.
Returns a rule specifying that tk should not be returned from parsing; i.e. tk’s function is purely syntactic. The end-of-file is always treated as a delimiter.
Returns a rule specifying the following actions take place when tk is parsed:
Returns a rule specifying the following actions take place when tk is parsed:
prec:parse1 is called with binding-power bp.
prec:parse1; the resulting value is incorporated into the
expression being built. Otherwise, the list of sop and the
expression returned from prec:parse1 is incorporated.
Returns a rule declaring the left-binding-precedence of the token tk is lbp and specifying the following actions take place when tk is parsed:
Returns a rule declaring the left-binding-precedence of the token tk is bp and specifying the following actions take place when tk is parsed:
Returns a rule declaring the left-binding-precedence of the token tk is lbp and specifying the following actions take place when tk is parsed:
Returns a rule specifying the following actions take place when tk is parsed:
Returns rules specifying the following actions take place when tk is parsed:
Parsing of commentfix syntax differs from the others in several ways. It reads directly from input without tokenizing; It calls stp but does not return its value; nay any value. I added the stp argument so that comment text could be echoed.
Returns a rule specifying the following actions take place when tk is parsed:
0 until the token
match is reached. If the token sep does not appear between
each pair of expressions parsed, a warning is issued.
Returns a rule declaring the left-binding-precedence of the token tk is lbp and specifying the following actions take place when tk is parsed:
0 until the token
match is reached. If the token sep does not appear between
each pair of expressions parsed, a warning is issued.
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| 3.3.2 Standard Formatted Output | ’printf | |
| 3.3.3 Standard Formatted Input | ’scanf |
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requires printf and scanf and additionally defines
the symbols:
Defined to be (current-input-port).
Defined to be (current-output-port).
Defined to be (current-error-port).
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Each function converts, formats, and outputs its arg1 … arguments according to the control string format argument and returns the number of characters output.
printf sends its output to the port (current-output-port).
fprintf sends its output to the port port. sprintf
string-set!s locations of the non-constant string argument
str to the output characters.
Two extensions of sprintf return new strings. If the first
argument is #f, then the returned string’s length is as many
characters as specified by the format and data; if the first
argument is a non-negative integer k, then the length of the
returned string is also bounded by k.
The string format contains plain characters which are copied to the output stream, and conversion specifications, each of which results in fetching zero or more of the arguments arg1 …. The results are undefined if there are an insufficient number of arguments for the format. If format is exhausted while some of the arg1 … arguments remain unused, the excess arg1 … arguments are ignored.
The conversion specifications in a format string have the form:
% [ flags ] [ width ] [ . precision ] [ type ] conversion
An output conversion specifications consist of an initial ‘%’ character followed in sequence by:
Left-justify the result in the field. Normally the result is right-justified.
For the signed ‘%d’ and ‘%i’ conversions and all inexact conversions, prefix a plus sign if the value is positive.
For the signed ‘%d’ and ‘%i’ conversions, if the result doesn’t start with a plus or minus sign, prefix it with a space character instead. Since the ‘+’ flag ensures that the result includes a sign, this flag is ignored if both are specified.
For inexact conversions, ‘#’ specifies that the result should always include a decimal point, even if no digits follow it. For the ‘%g’ and ‘%G’ conversions, this also forces trailing zeros after the decimal point to be printed where they would otherwise be elided.
For the ‘%o’ conversion, force the leading digit to be ‘0’, as
if by increasing the precision. For ‘%x’ or ‘%X’, prefix a
leading ‘0x’ or ‘0X’ (respectively) to the result. This
doesn’t do anything useful for the ‘%d’, ‘%i’, or ‘%u’
conversions. Using this flag produces output which can be parsed by the
scanf functions with the ‘%i’ conversion (see section Standard Formatted Input).
Pad the field with zeros instead of spaces. The zeros are placed after any indication of sign or base. This flag is ignored if the ‘-’ flag is also specified, or if a precision is specified for an exact converson.
Alternatively, if the field width is ‘*’, the next argument in the argument list (before the actual value to be printed) is used as the field width. The width value must be an integer. If the value is negative it is as though the ‘-’ flag is set (see above) and the absolute value is used as the field width.
Alternatively, if the precision is ‘.*’, the next argument in the argument list (before the actual value to be printed) is used as the precision. The value must be an integer, and is ignored if negative. If you specify ‘*’ for both the field width and precision, the field width argument precedes the precision argument. The ‘.*’ precision is an enhancement. C library versions may not accept this syntax.
For the ‘%f’, ‘%e’, and ‘%E’ conversions, the precision
specifies how many digits follow the decimal-point character. The
default precision is 6. If the precision is explicitly 0,
the decimal point character is suppressed.
For the ‘%g’ and ‘%G’ conversions, the precision specifies how
many significant digits to print. Significant digits are the first
digit before the decimal point, and all the digits after it. If the
precision is 0 or not specified for ‘%g’ or ‘%G’, it is
treated like a value of 1. If the value being printed cannot be
expressed accurately in the specified number of digits, the value is
rounded to the nearest number that fits.
For exact conversions, if a precision is supplied it specifies the minimum number of digits to appear; leading zeros are produced if necessary. If a precision is not supplied, the number is printed with as many digits as necessary. Converting an exact ‘0’ with an explicit precision of zero produces no characters.
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Print an integer as a signed decimal number. ‘%d’ and ‘%i’
are synonymous for output, but are different when used with scanf
for input (see section Standard Formatted Input).
Print an integer as an unsigned octal number.
Print an integer as an unsigned decimal number.
Print an integer as an unsigned hexadecimal number. ‘%x’ prints using the digits ‘0123456789abcdef’. ‘%X’ prints using the digits ‘0123456789ABCDEF’.
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Print a floating-point number in fixed-point notation.
Print a floating-point number in exponential notation. ‘%e’ prints ‘e’ between mantissa and exponont. ‘%E’ prints ‘E’ between mantissa and exponont.
Print a floating-point number in either normal or exponential notation, whichever is more appropriate for its magnitude. Unless an ‘#’ flag has been supplied trailing zeros after a decimal point will be stripped off. ‘%g’ prints ‘e’ between mantissa and exponont. ‘%G’ prints ‘E’ between mantissa and exponent.
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Print a single character. The ‘-’ flag is the only one which can be specified. It is an error to specify a precision.
Print a string. The ‘-’ flag is the only one which can be specified. A precision specifies the maximum number of characters to output; otherwise all characters in the string are output.
Print a scheme expression. The ‘-’ flag left-justifies the output.
The ‘#’ flag specifies that strings and characters should be quoted
as by write (which can be read using read); otherwise,
output is as display prints. A precision specifies the maximum
number of characters to output; otherwise as many characters as needed
are output.
Note: ‘%a’ and ‘%A’ are SLIB extensions.
Print a literal ‘%’ character. No argument is consumed. It is an error to specifiy flags, field width, precision, or type modifiers with ‘%%’.
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Each function reads characters, interpreting them according to the control string format argument.
scanf-read-list returns a list of the items specified as far as
the input matches format. scanf, fscanf, and
sscanf return the number of items successfully matched and
stored. scanf, fscanf, and sscanf also set the
location corresponding to arg1 … using the methods:
set!
set-car!
set-cdr!
vector-set!
substring-move-left!
The argument to a substring expression in arg1 … must
be a non-constant string. Characters will be stored starting at the
position specified by the second argument to substring. The
number of characters stored will be limited by either the position
specified by the third argument to substring or the length of the
matched string, whichever is less.
The control string, format, contains conversion specifications and other characters used to direct interpretation of input sequences. The control string contains:
Unless the specification contains the ‘n’ conversion character (described below), a conversion specification directs the conversion of the next input field. The result of a conversion specification is returned in the position of the corresponding argument points, unless ‘*’ indicates assignment suppression. Assignment suppression provides a way to describe an input field to be skipped. An input field is defined as a string of characters; it extends to the next inappropriate character or until the field width, if specified, is exhausted.
Note: This specification of format strings differs from the ANSI C and POSIX specifications. In SLIB, white space before an input field is not skipped unless white space appears before the conversion specification in the format string. In order to write format strings which work identically with ANSI C and SLIB, prepend whitespace to all conversion specifications except ‘[’ and ‘c’.
The conversion code indicates the interpretation of the input field; For a suppressed field, no value is returned. The following conversion codes are legal:
A single % is expected in the input at this point; no value is returned.
A decimal integer is expected.
An unsigned decimal integer is expected.
An octal integer is expected.
A hexadecimal integer is expected.
An integer is expected. Returns the value of the next input item, interpreted according to C conventions; a leading ‘0’ implies octal, a leading ‘0x’ implies hexadecimal; otherwise, decimal is assumed.
Returns the total number of bytes (including white space) read by
scanf. No input is consumed by %n.
A floating-point number is expected. The input format for floating-point numbers is an optionally signed string of digits, possibly containing a radix character ‘.’, followed by an optional exponent field consisting of an ‘E’ or an ‘e’, followed by an optional ‘+’, ‘-’, or space, followed by an integer.
Width characters are expected. The normal skip-over-white-space is suppressed in this case; to read the next non-space character, use ‘%1s’. If a field width is given, a string is returned; up to the indicated number of characters is read.
A character string is expected The input field is terminated by a
white-space character. scanf cannot read a null string.
Indicates string data and the normal skip-over-leading-white-space is suppressed. The left bracket is followed by a set of characters, called the scanset, and a right bracket; the input field is the maximal sequence of input characters consisting entirely of characters in the scanset. ‘^’, when it appears as the first character in the scanset, serves as a complement operator and redefines the scanset as the set of all characters not contained in the remainder of the scanset string. Construction of the scanset follows certain conventions. A range of characters may be represented by the construct first-last, enabling ‘[0123456789]’ to be expressed ‘[0-9]’. Using this convention, first must be lexically less than or equal to last; otherwise, the dash stands for itself. The dash also stands for itself when it is the first or the last character in the scanset. To include the right square bracket as an element of the scanset, it must appear as the first character (possibly preceded by a ‘^’) of the scanset, in which case it will not be interpreted syntactically as the closing bracket. At least one character must match for this conversion to succeed.
The scanf functions terminate their conversions at end-of-file,
at the end of the control string, or when an input character conflicts
with the control string. In the latter case, the offending character is
left unread in the input stream.
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| 3.4.1 Getopt | Command Line option parsing | |
| 3.4.3 Command Line | A command line reader for Scheme shells | |
| 3.4.4 Parameter lists | ’parameters | |
| 3.4.5 Getopt Parameter lists | ’getopt-parameters | |
| 3.4.6 Filenames | ’glob or ’filename | |
| 3.4.7 Batch | ’batch |
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This routine implements Posix command line argument parsing. Notice
that returning values through global variables means that getopt
is not reentrant.
Is the index of the current element of the command line. It is initially one. In order to parse a new command line or reparse an old one, *opting* must be reset.
Is set by getopt to the (string) option-argument of the current option.
Returns the next option letter in argv (starting from
(vector-ref argv *optind*)) that matches a letter in
optstring. argv is a vector or list of strings, the 0th of
which getopt usually ignores. argc is the argument count, usually
the length of argv. optstring is a string of recognized
option characters; if a character is followed by a colon, the option
takes an argument which may be immediately following it in the string or
in the next element of argv.
*optind* is the index of the next element of the argv vector
to be processed. It is initialized to 1 by ‘getopt.scm’, and
getopt updates it when it finishes with each element of
argv.
getopt returns the next option character from argv that
matches a character in optstring, if there is one that matches.
If the option takes an argument, getopt sets the variable
*optarg* to the option-argument as follows:
getopt returns an error
indication.
If, when getopt is called, the string (vector-ref argv
*optind*) either does not begin with the character #\- or is
just "-", getopt returns #f without changing
*optind*. If (vector-ref argv *optind*) is the string
"--", getopt returns #f after incrementing
*optind*.
If getopt encounters an option character that is not contained in
optstring, it returns the question-mark #\? character. If
it detects a missing option argument, it returns the colon character
#\: if the first character of optstring was a colon, or a
question-mark character otherwise. In either case, getopt sets
the variable getopt:opt to the option character that caused the
error.
The special option "--" can be used to delimit the end of the
options; #f is returned, and "--" is skipped.
RETURN VALUE
getopt returns the next option character specified on the command
line. A colon #\: is returned if getopt detects a missing
argument and the first character of optstring was a colon
#\:.
A question-mark #\? is returned if getopt encounters an
option character not in optstring or detects a missing argument
and the first character of optstring was not a colon #\:.
Otherwise, getopt returns #f when all command line options
have been parsed.
Example:
#! /usr/local/bin/scm ;;;This code is SCM specific. (define argv (program-arguments)) (require 'getopt) (define opts ":a:b:cd") (let loop ((opt (getopt (length argv) argv opts))) (case opt ((#\a) (print "option a: " *optarg*)) ((#\b) (print "option b: " *optarg*)) ((#\c) (print "option c")) ((#\d) (print "option d")) ((#\?) (print "error" getopt:opt)) ((#\:) (print "missing arg" getopt:opt)) ((#f) (if (< *optind* (length argv)) (print "argv[" *optind* "]=" (list-ref argv *optind*))) (set! *optind* (+ *optind* 1)))) (if (< *optind* (length argv)) (loop (getopt (length argv) argv opts)))) (slib:exit)
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The procedure getopt-- is an extended version of getopt
which parses long option names of the form
‘--hold-the-onions’ and ‘--verbosity-level=extreme’.
Getopt-- behaves as getopt except for non-empty
options beginning with ‘--’.
Options beginning with ‘--’ are returned as strings rather than
characters. If a value is assigned (using ‘=’) to a long option,
*optarg* is set to the value. The ‘=’ and value are
not returned as part of the option string.
No information is passed to getopt-- concerning which long
options should be accepted or whether such options can take arguments.
If a long option did not have an argument, *optarg will be set to
#f. The caller is responsible for detecting and reporting
errors.
(define opts ":-:b:")
(define argc 5)
(define argv '("foo" "-b9" "--f1" "--2=" "--g3=35234.342" "--"))
(define *optind* 1)
(define *optarg* #f)
(require 'qp)
(do ((i 5 (+ -1 i)))
((zero? i))
(define opt (getopt-- argc argv opts))
(print *optind* opt *optarg*)))
-|
2 #\b "9"
3 "f1" #f
4 "2" ""
5 "g3" "35234.342"
5 #f "35234.342"
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read-command converts a command line into a list of strings
suitable for parsing by getopt. The syntax of command lines
supported resembles that of popular shells. read-command
updates port to point to the first character past the command
delimiter.
If an end of file is encountered in the input before any characters are found that can begin an object or comment, then an end of file object is returned.
The port argument may be omitted, in which case it defaults to the
value returned by current-input-port.
The fields into which the command line is split are delimited by
whitespace as defined by char-whitespace?. The end of a command
is delimited by end-of-file or unescaped semicolon (<;>) or
<newline>. Any character can be literally included in a field by
escaping it with a backslach (<\>).
The initial character and types of fields recognized are:
The next character has is taken literally and not interpreted as a field delimiter. If <\> is the last character before a <newline>, that <newline> is just ignored. Processing continues from the characters after the <newline> as though the backslash and <newline> were not there.
The characters up to the next unescaped <"> are taken literally, according to [R4RS] rules for literal strings (see Strings in Revised(4) Scheme).
One scheme expression is read starting with this character. The
read expression is evaluated, converted to a string
(using display), and replaces the expression in the returned
field.
Semicolon delimits a command. Using semicolons more than one command can appear on a line. Escaped semicolons and semicolons inside strings do not delimit commands.
The comment field differs from the previous fields in that it must be
the first character of a command or appear after whitespace in order to
be recognized. <#> can be part of fields if these conditions are
not met. For instance, ab#c is just the field ab#c.
Introduces a comment. The comment continues to the end of the line on
which the semicolon appears. Comments are treated as whitespace by
read-dommand-line and backslashes before <newline>s in
comments are also ignored.
read-options-file converts an options file into a list of
strings suitable for parsing by getopt. The syntax of options
files is the same as the syntax for command
lines, except that <newline>s do not terminate reading (only <;>
or end of file).
If an end of file is encountered before any characters are found that can begin an object or comment, then an end of file object is returned.
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Arguments to procedures in scheme are distinguished from each other by their position in the procedure call. This can be confusing when a procedure takes many arguments, many of which are not often used.
A parameter-list is a way of passing named information to a procedure. Procedures are also defined to set unused parameters to default values, check parameters, and combine parameter lists.
A parameter has the form (parameter-name value1
…). This format allows for more than one value per
parameter-name.
A parameter-list is a list of parameters, each with a different parameter-name.
Returns an empty parameter-list with slots for parameter-names.
parameter-name must name a valid slot of parameter-list.
parameter-list-ref returns the value of parameter
parameter-name of parameter-list.
Returns parameter-list with parameter1 … merged in.
expanders is a list of procedures whose order matches the order of
the parameter-names in the call to make-parameter-list
which created parameter-list. For each non-false element of
expanders that procedure is mapped over the corresponding
parameter value and the returned parameter lists are merged into
parameter-list.
This process is repeated until parameter-list stops growing. The
value returned from parameter-list-expand is unspecified.
defaulters is a list of procedures whose order matches the order
of the parameter-names in the call to make-parameter-list
which created parameter-list. fill-empty-parameters
returns a new parameter-list with each empty parameter replaced with the
list returned by calling the corresponding defaulter with
parameter-list as its argument.
checks is a list of procedures whose order matches the order of
the parameter-names in the call to make-parameter-list
which created parameter-list.
check-parameters returns parameter-list if each check
of the corresponding parameter-list returns non-false. If some
check returns #f an error is signaled.
In the following procedures arities is a list of symbols. The
elements of arities can be:
singleRequires a single parameter.
optionalA single parameter or no parameter is acceptable.
booleanA single boolean parameter or zero parameters is acceptable.
naryAny number of parameters are acceptable.
nary1One or more of parameters are acceptable.
Returns parameter-list converted to an argument list. Parameters
of arity type single and boolean are converted to
the single value associated with them. The other arity types are
converted to lists of the value(s) of type types.
positions is a list of positive integers whose order matches the
order of the parameter-names in the call to
make-parameter-list which created parameter-list. The
integers specify in which argument position the corresponding parameter
should appear.
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(require 'getopt-parameters)
Returns argv converted to a parameter-list. optnames are
the parameter-names. aliases is a list of lists of strings and
elements of optnames. Each of these strings which have length of
1 will be treated as a single <-> option by getopt. Longer
strings will be treated as long-named options (see section getopt–).
Like getopt->parameter-list, but converts argv to an
argument-list as specified by optnames, positions,
arities, types, defaulters, checks, and
aliases.
These getopt functions can be used with SLIB relational
databases. For an example, See section make-command-server.
If errors are encountered while processing options, directions for using
the options are printed to current-error-port.
(begin
(set! *optind* 1)
(getopt->parameter-list
2
'("cmd" "-?")
'(flag number symbols symbols string flag2 flag3 num2 num3)
'(boolean optional nary1 nary single boolean boolean nary nary)
'(boolean integer symbol symbol string boolean boolean integer integer)
'(("flag" flag)
("f" flag)
("Flag" flag2)
("B" flag3)
("optional" number)
("o" number)
("nary1" symbols)
("N" symbols)
("nary" symbols)
("n" symbols)
("single" string)
("s" string)
("a" num2)
("Abs" num3))))
-|
Usage: cmd [OPTION ARGUMENT ...] ...
-f, --flag
-o, --optional=<number>
-n, --nary=<symbols> ...
-N, --nary1=<symbols> ...
-s, --single=<string>
--Flag
-B
-a <num2> ...
--Abs=<num3> ...
ERROR: getopt->parameter-list "unrecognized option" "-?"
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(require 'filename) or (require 'glob)
Returns a predicate which returns a non-false value if its string argument matches (the string) pattern, false otherwise. Filename matching is like glob expansion described the bash manpage, except that names beginning with ‘.’ are matched and ‘/’ characters are not treated specially.
These functions interpret the following characters specially in pattern strings:
Matches any string, including the null string.
Matches any single character.
Matches any one of the enclosed characters. A pair of characters separated by a minus sign (-) denotes a range; any character lexically between those two characters, inclusive, is matched. If the first character following the ‘[’ is a ‘!’ or a ‘^’ then any character not enclosed is matched. A ‘-’ or ‘]’ may be matched by including it as the first or last character in the set.
Returns a function transforming a single string argument according to
glob patterns pattern and template. pattern and
template must have the same number of wildcard specifications,
which need not be identical. pattern and template may have
a different number of literal sections. If an argument to the function
matches pattern in the sense of filename:match?? then it
returns a copy of template in which each wildcard specification is
replaced by the part of the argument matched by the corresponding
wildcard specification in pattern. A * wildcard matches
the longest leftmost string possible. If the argument does not match
pattern then false is returned.
((filename:substitute?? "scm_[0-9]*.html" "scm5c4_??.htm") "scm_10.html") ⇒ "scm5c4_10.htm" ((filename:substitute?? "??" "beg?mid?end") "AZ") ⇒ "begAmidZend" ((filename:substitute?? "*na*" "?NA?") "banana") ⇒ "banaNA"
str can be a string or a list of strings. Returns a new string
(or strings) similar to str but with the suffix string old
removed and the suffix string new appended. If the end of
str does not match old, an error is signaled.
(replace-suffix "/usr/local/lib/slib/batch.scm" ".scm" ".c") ⇒ "/usr/local/lib/slib/batch.c"
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The batch procedures provide a way to write and execute portable scripts
for a variety of operating systems. Each batch: procedure takes
as its first argument a parameter-list (see section Parameter lists). This
parameter-list argument parms contains named associations. Batch
currently uses 2 of these:
batch-portThe port on which to write lines of the batch file.
batch-dialectThe syntax of batch file to generate. Currently supported are:
‘batch.scm’ uses 2 enhanced relational tables (see section Database Utilities) to store information linking the names of
operating-systems to batch-dialectes.
Defines operating-system and batch-dialect tables and adds
the domain operating-system to the enhanced relational database
database.
Is batch’s best guess as to which operating-system it is running under.
batch:platform is set to (software-type)
(see section Configuration) unless (software-type) is unix,
in which case finer distinctions are made.
proc should be a procedure of one argument. If file is an
output-port, batch:call-with-output-script writes an appropriate
header to file and then calls proc with file as the
only argument. If file is a string,
batch:call-with-output-script opens a output-file of name
file, writes an appropriate header to file, and then calls
proc with the newly opened port as the only argument. Otherwise,
batch:call-with-output-script acts as if it was called with the
result of (current-output-port) as its third argument.
The procedure proc must accept at least one argument and return
#t if successful, #f if not.
batch:apply-chop-to-fit calls proc with arg1,
arg2, …, and chunk, where chunk is a subset of
list. batch:apply-chop-to-fit tries proc with
successively smaller subsets of list until either proc
returns non-false, or the chunks become empty.
The rest of the batch: procedures write (or execute if
batch-dialect is system) commands to the batch port which
has been added to parms or (copy-tree parms) by the
code:
(adjoin-parameters! parms (list 'batch-port port))
Calls batch:try-system (below) with arguments, but signals an
error if batch:try-system returns #f.
These functions return a non-false value if the command was successfully
translated into the batch dialect and #f if not. In the case of
the system dialect, the value is non-false if the operation
suceeded.
Writes a command to the batch-port in parms which executes
the program named string1 with arguments string2 ….
Writes a command to the batch-port in parms which executes
the batch script named string1 with arguments string2
….
Note: batch:run-script and batch:try-system are not the
same for some operating systems (VMS).
Writes comment lines line1 … to the batch-port in
parms.
Writes commands to the batch-port in parms which create a
file named file with contents line1 ….
Writes a command to the batch-port in parms which deletes
the file named file.
Writes a command to the batch-port in parms which renames
the file old-name to new-name.
In addition, batch provides some small utilities very useful for writing scripts:
path can be a string or a list of strings. Returns path sans any prefixes ending with a character of the second argument. This can be used to derive a filename moved locally from elsewhere.
(truncate-up-to "/usr/local/lib/slib/batch.scm" "/") ⇒ "batch.scm"
Returns a new string consisting of all the strings string1 … in order appended together with the string joiner between each adjacent pair.
Returns a new list consisting of the elements of list2 ordered so
that if some elements of list1 are equal? to elements of
list2, then those elements will appear first and in the order of
list1.
Returns a new list consisting of the elements of list1 ordered so
that if some elements of list2 are equal? to elements of
list1, then those elements will appear last and in the order of
list2.
Returns its best guess for the batch-dialect to be used for the
operating-system named osname. os->batch-dialect uses the
tables added to database by batch:initialize!.
Here is an example of the use of most of batch’s procedures:
(require 'database-utilities) (require 'parameters) (require 'batch) (require 'glob) (define batch (create-database #f 'alist-table)) (batch:initialize! batch) (define my-parameters (list (list 'batch-dialect (os->batch-dialect batch:platform)) (list 'platform batch:platform) (list 'batch-port (current-output-port)))) ;gets filled in later (batch:call-with-output-script my-parameters "my-batch" (lambda (batch-port) (adjoin-parameters! my-parameters (list 'batch-port batch-port)) (and (batch:comment my-parameters "================ Write file with C program.") (batch:rename-file my-parameters "hello.c" "hello.c~") (batch:lines->file my-parameters "hello.c" "#include <stdio.h>" "int main(int argc, char **argv)" "{" " printf(\"hello world\\n\");" " return 0;" "}" ) (batch:system my-parameters "cc" "-c" "hello.c") (batch:system my-parameters "cc" "-o" "hello" (replace-suffix "hello.c" ".c" ".o")) (batch:system my-parameters "hello") (batch:delete-file my-parameters "hello") (batch:delete-file my-parameters "hello.c") (batch:delete-file my-parameters "hello.o") (batch:delete-file my-parameters "my-batch") )))
Produces the file ‘my-batch’:
#!/bin/sh
# "my-batch" build script created Sat Jun 10 21:20:37 1995
# ================ Write file with C program.
mv -f hello.c hello.c~
rm -f hello.c
echo '#include <stdio.h>'>>hello.c
echo 'int main(int argc, char **argv)'>>hello.c
echo '{'>>hello.c
echo ' printf("hello world\n");'>>hello.c
echo ' return 0;'>>hello.c
echo '}'>>hello.c
cc -c hello.c
cc -o hello hello.o
hello
rm -f hello
rm -f hello.c
rm -f hello.o
rm -f my-batch
When run, ‘my-batch’ prints:
bash$ my-batch mv: hello.c: No such file or directory hello world
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| 3.6.1 Generic-Write | ’generic-write | |
| 3.6.2 Object-To-String | ’object->string | |
| 3.6.3 Pretty-Print | ’pretty-print, ’pprint-file |
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generic-write is a procedure that transforms a Scheme data value
(or Scheme program expression) into its textual representation and
prints it. The interface to the procedure is sufficiently general to
easily implement other useful formatting procedures such as pretty
printing, output to a string and truncated output.
Scheme data value to transform.
Boolean, controls whether characters and strings are quoted.
Extended boolean, selects format:
single line format
pretty-print (value = max nb of chars per line)
Procedure of 1 argument of string type, called repeatedly with
successive substrings of the textual representation. This procedure can
return #f to stop the transformation.
The value returned by generic-write is undefined.
Examples:
(write obj) ≡ (generic-write obj #f #f display-string) (display obj) ≡ (generic-write obj #t #f display-string)
where
display-string ≡ (lambda (s) (for-each write-char (string->list s)) #t)
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pretty-prints obj on port. If port is not
specified, current-output-port is used.
Example:
(pretty-print '((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15)
(16 17 18 19 20) (21 22 23 24 25)))
-| ((1 2 3 4 5)
-| (6 7 8 9 10)
-| (11 12 13 14 15)
-| (16 17 18 19 20)
-| (21 22 23 24 25))
Pretty-prints all the code in infile. If outfile is
specified, the output goes to outfile, otherwise it goes to
(current-output-port).
infile is a port or a string naming an existing file. Scheme source code expressions and definitions are read from the port (or file) and proc is applied to them sequentially.
outfile is a port or a string. If no outfile is specified
then current-output-port is assumed. These expanded expressions
are then pretty-printed to this port.
Whitepsace and comments (introduced by ;) which are not part of
scheme expressions are reproduced in the output. This procedure does
not affect the values returned by current-input-port and
current-output-port.
pprint-filter-file can be used to pre-compile macro-expansion and
thus can reduce loading time. The following will write into
‘exp-code.scm’ the result of expanding all defmacros in
‘code.scm’.
(require 'pprint-file) (require 'defmacroexpand) (defmacro:load "my-macros.scm") (pprint-filter-file "code.scm" defmacro:expand* "exp-code.scm")
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| 3.7.1 Time Zone | ||
| 3.7.2 Posix Time | ’posix-time | |
| 3.7.3 Common-Lisp Time | ’common-lisp-time |
If (provided? 'current-time):
The procedures current-time, difftime, and
offset-time deal with a calendar time datatype
which may or may not be disjoint from other Scheme datatypes.
Returns the time since 00:00:00 GMT, January 1, 1970, measured in
seconds. Note that the reference time is different from the reference
time for get-universal-time in Common-Lisp Time.
Returns the difference (number of seconds) between twe calendar times: caltime1 - caltime0. caltime0 may also be a number.
Returns the calendar time of caltime offset by offset number
of seconds (+ caltime offset).
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(require ’time-zone)
POSIX standards specify several formats for encoding time-zone rules.
If the first character of <pathname> is ‘/’, then <pathname> specifies the absolute pathname of a tzfile(5) format time-zone file. Otherwise, <pathname> is interpreted as a pathname within tzfile:vicinity (/usr/lib/zoneinfo/) naming a tzfile(5) format time-zone file.
The string <std> consists of 3 or more alphabetic characters.
<offset> specifies the time difference from GMT. The <offset>
is positive if the local time zone is west of the Prime Meridian and
negative if it is east. <offset> can be the number of hours or
hours and minutes (and optionally seconds) separated by ‘:’. For
example, -4:30.
<dst> is the at least 3 alphabetic characters naming the local daylight-savings-time.
<doffset> specifies the offset from the Prime Meridian when daylight-savings-time is in effect.
The non-tzfile formats can optionally be followed by transition times specifying the day and time when a zone changes from standard to daylight-savings and back again.
The <time>s are specified like the <offset>s above, except that leading ‘+’ and ‘-’ are not allowed.
Each <date> has one of the formats:
specifies the Julian day with <day> between 1 and 365. February 29 is never counted and cannot be referenced.
This specifies the Julian day with n between 0 and 365. February 29 is counted in leap years and can be specified.
This specifies day <day> (0 <= <day> <= 6) of week <week> (1 <= <week> <= 5) of month <month> (1 <= <month> <= 12). Week 1 is the first week in which day d occurs and week 5 is the last week in which day <day> occurs. Day 0 is a Sunday.
is a datatype encoding how many hours from Greenwich Mean Time the local time is, and the Daylight Savings Time rules for changing it.
Creates and returns a time-zone object specified by the string
TZ-string. If time-zone cannot interpret TZ-string,
#f is returned.
tz is a time-zone object. tz:params returns a list of
three items:
tz:params is unaffected by the default timezone; inquiries can be
made of any timezone at any calendar time.
The rest of these procedures and variables are provided for POSIX compatability. Because of shared state they are not thread-safe.
Returns the default time-zone.
Sets (and returns) the default time-zone to tz.
Sets (and returns) the default time-zone to that specified by TZ-string.
tzset also sets the variables *timezone*, daylight?,
and tzname. This function is automatically called by the time
conversion procedures which depend on the time zone (see section Time and Date).
Contains the difference, in seconds, between Greenwich Mean Time and
local standard time (for example, in the U.S. Eastern time zone (EST),
timezone is 5*60*60). *timezone* is initialized by tzset.
is #t if the default timezone has rules for Daylight Savings
Time. Note: daylight? does not tell you when Daylight
Savings Time is in effect, just that the default zone sometimes has
Daylight Savings Time.
is a vector of strings. Index 0 has the abbreviation for the standard timezone; If daylight?, then index 1 has the abbreviation for the Daylight Savings timezone.
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is a datatype encapsulating time.
(abbreviated UTC) is a vector of integers representing time:
decode-universal-time.
decode-universal-time.
Converts the calendar time caltime to UTC and returns it.
Returns caltime converted to UTC relative to timezone tz.
converts the calendar time caltime to a vector of integers
expressed relative to the user’s time zone. localtime sets the
variable *timezone* with the difference between Coordinated
Universal Time (UTC) and local standard time in seconds
(see section tzset).
Converts a vector of integers in GMT Coordinated Universal Time (UTC) format to a calendar time.
Converts a vector of integers in local Coordinated Universal Time (UTC) format to a calendar time.
Converts a vector of integers in Coordinated Universal Time (UTC) format (relative to time-zone tz) to calendar time.
Converts the vector of integers caltime in Coordinated
Universal Time (UTC) format into a string of the form
"Wed Jun 30 21:49:08 1993".
Equivalent to (asctime (gmtime caltime)),
(asctime (localtime caltime)), and
(asctime (localtime caltime tz)), respectively.
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Equivalent to (decode-universal-time (get-universal-time)).
Returns the current time as Universal Time, number of seconds
since 00:00:00 Jan 1, 1900 GMT. Note that the reference time is
different from current-time.
Converts univtime to Decoded Time format. Nine values are returned:
gmtime and localtime.
gmtime and localtime.
Notice that the values returned by decode-universal-time do not
match the arguments to encode-universal-time.
Converts the arguments in Decoded Time format to Universal Time format. If time-zone is not specified, the returned time is adjusted for daylight saving time. Otherwise, no adjustment is performed.
Notice that the values returned by decode-universal-time do not
match the arguments to encode-universal-time.
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| 3.8.1 Tektronix Graphics Support |
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Note: The Tektronix graphics support files need more work, and are not complete.
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The Tektronix 4000 series graphics protocol gives the user a 1024 by 1024 square drawing area. The origin is in the lower left corner of the screen. Increasing y is up and increasing x is to the right.
The graphics control codes are sent over the current-output-port and can be mixed with regular text and ANSI or other terminal control sequences.
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The graphics control codes are sent over the current-output-port and can be mixed with regular text and ANSI or other terminal control sequences.
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Schmooz is a simple, lightweight markup language for interspersing Texinfo documentation with Scheme source code. Schmooz does not create the top level Texinfo file; it creates ‘txi’ files which can be imported into the documentation using the Texinfo command ‘@include’.
(require 'schmooz) defines the function schmooz, which is
used to process files. Files containing schmooz documentation should
not contain (require 'schmooz).
Filenamescm should be a string ending with ‘scm’ naming an
existing file containing Scheme source code. schmooz extracts
top-level comments containing schmooz commands from filenamescm
and writes the converted Texinfo source to a file named
filenametxi.
Filename should be a string naming an existing file containing
Texinfo source code. For every occurrence of the string ‘@include
filenametxi’ within that file, schmooz calls itself with
the argument ‘filenamescm’.
Schmooz comments are distinguished (from non-schmooz comments) by their first line, which must start with an at-sign (@) preceded by one or more semicolons (;). A schmooz comment ends at the first subsequent line which does not start with a semicolon. Currently schmooz comments are recognized only at top level.
Schmooz comments are copied to the Texinfo output file with the leading contiguous semicolons removed. Certain character sequences starting with at-sign are treated specially. Others are copied unchanged.
A schmooz comment starting with ‘@body’ must be followed by a Scheme definition. All comments between the ‘@body’ line and the definition will be included in a Texinfo definition, either a ‘@defun’ or a ‘@defvar’, depending on whether a procedure or a variable is being defined.
Within the text of that schmooz comment, at-sign
followed by ‘0’ will be replaced by @code{procedure-name}
if the following definition is of a procedure; or
@var{variable} if defining a variable.
An at-sign followed by a non-zero digit will expand to the variable citation of that numbered argument: ‘@var{argument-name}’.
If more than one definition follows a ‘@body’ comment line without an intervening blank or comment line, then those definitions will be included in the same Texinfo definition using ‘@defvarx’ or ‘@defunx’, depending on whether the first definition is of a variable or of a procedure.
Schmooz can figure out whether a definition is of a procedure if it is of the form:
‘(define (<identifier> <arg> ...) <expression>)’
or if the left hand side of the definition is some form ending in a lambda expression. Obviously, it can be fooled. In order to force recognition of a procedure definition, start the documentation with ‘@args’ instead of ‘@body’. ‘@args’ should be followed by the argument list of the function being defined, which may be enclosed in parentheses and delimited by whitespace, (as in Scheme), enclosed in braces and separated by commas, (as in Texinfo), or consist of the remainder of the line, separated by whitespace.
For example:
;;@args arg1 args ... ;;@0 takes argument @1 and any number of @2 (define myfun (some-function-returning-magic))
Will result in:
@defun myfun arg1 args @dots{}
@code{myfun} takes argument @var{arg1} and any number of @var{args}
@end defun
‘@args’ may also be useful for indicating optional arguments by name. If ‘@args’ occurs inside a schmooz comment section, rather than at the beginning, then it will generate a ‘@defunx’ line with the arguments supplied.
If the first at-sign in a schmooz comment is immediately followed by whitespace, then the comment will be expanded to whatever follows that whitespace. If the at-sign is followed by a non-whitespace character then the at-sign will be included as the first character of the expansion. This feature is intended to make it easy to include Texinfo directives in schmooz comments.
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| 4.1 Bit-Twiddling | ’logical | |
| 4.2 Modular Arithmetic | ’modular | |
| 4.3 Prime Numbers | ’factor | |
| 4.4 Random Numbers | ’random | |
| 4.5 Cyclic Checksum | ’make-crc | |
| 4.6 Plotting on Character Devices | ’charplot | |
| 4.7 Root Finding | ’root | |
| 4.8 Commutative Rings | ’commutative-ring | |
| 4.9 Determinant | ’determinant |
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The bit-twiddling functions are made available through the use of the
logical package. logical is loaded by inserting
(require 'logical) before the code that uses these
functions. These functions behave as though operating on integers
in two’s-complement representation.
Returns the integer which is the bit-wise AND of the two integer arguments.
Example:
(number->string (logand #b1100 #b1010) 2) ⇒ "1000"
Returns the integer which is the bit-wise OR of the two integer arguments.
Example:
(number->string (logior #b1100 #b1010) 2) ⇒ "1110"
Returns the integer which is the bit-wise XOR of the two integer arguments.
Example:
(number->string (logxor #b1100 #b1010) 2) ⇒ "110"
Returns the integer which is the 2s-complement of the integer argument.
Example:
(number->string (lognot #b10000000) 2) ⇒ "-10000001" (number->string (lognot #b0) 2) ⇒ "-1"
Returns an integer composed of some bits from integer n0 and some from integer n1. A bit of the result is taken from n0 if the corresponding bit of integer mask is 1 and from n1 if that bit of mask is 0.
(logtest j k) ≡ (not (zero? (logand j k))) (logtest #b0100 #b1011) ⇒ #f (logtest #b0100 #b0111) ⇒ #t
Returns the number of bits in integer n. If integer is positive, the 1-bits in its binary representation are counted. If negative, the 0-bits in its two’s-complement binary representation are counted. If 0, 0 is returned.
Example:
(logcount #b10101010) ⇒ 4 (logcount 0) ⇒ 0 (logcount -2) ⇒ 1
(logbit? index j) ≡ (logtest (integer-expt 2 index) j) (logbit? 0 #b1101) ⇒ #t (logbit? 1 #b1101) ⇒ #f (logbit? 2 #b1101) ⇒ #t (logbit? 3 #b1101) ⇒ #t (logbit? 4 #b1101) ⇒ #f
Returns an integer the same as from except in the indexth bit,
which is 1 if bit is #t and 0 if bit is #f.
Example:
(number->string (copy-bit 0 0 #t) 2) ⇒ "1" (number->string (copy-bit 2 0 #t) 2) ⇒ "100" (number->string (copy-bit 2 #b1111 #f) 2) ⇒ "1011"
Returns the integer composed of the start (inclusive) through end (exclusive) bits of n. The startth bit becomes the 0-th bit in the result.
This function was called bit-extract in previous versions of SLIB.
Example:
(number->string (bit-field #b1101101010 0 4) 2) ⇒ "1010" (number->string (bit-field #b1101101010 4 9) 2) ⇒ "10110"
Returns an integer the same as to except possibly in the start (inclusive) through end (exclusive) bits, which are the same as those of from. The 0-th bit of from becomes the startth bit of the result.
Example:
(number->string (copy-bit-field #b1101101010 0 4 0) 2)
⇒ "1101100000"
(number->string (copy-bit-field #b1101101010 0 4 -1) 2)
⇒ "1101101111"
Returns an integer equivalent to
(inexact->exact (floor (* int (expt 2 count)))).
Example:
(number->string (ash #b1 3) 2) ⇒ "1000" (number->string (ash #b1010 -1) 2) ⇒ "101"
Returns the number of bits neccessary to represent n.
Example:
(integer-length #b10101010) ⇒ 8 (integer-length 0) ⇒ 0 (integer-length #b1111) ⇒ 4
Returns n raised to the non-negative integer exponent k.
Example:
(integer-expt 2 5) ⇒ 32 (integer-expt -3 3) ⇒ -27
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Returns a list of 3 integers (d x y) such that d = gcd(n1,
n2) = n1 * x + n2 * y.
Returns (quotient (+ -1 n) -2) for positive odd integer n.
Returns the non-negative integer characteristic of the ring formed when
modulus is used with modular: procedures.
Returns the integer (modulo n (modulus->integer
modulus)) in the representation specified by modulus.
The rest of these functions assume normalized arguments; That is, the arguments are constrained by the following table:
For all of these functions, if the first argument (modulus) is:
positive?Work as before. The result is between 0 and modulus.
zero?The arguments are treated as integers. An integer is returned.
negative?The arguments and result are treated as members of the integers modulo
(+ 1 (* -2 modulus)), but with symmetric
representation; i.e. (<= (- modulus) n
modulus).
If all the arguments are fixnums the computation will use only fixnums.
Returns #t if there exists an integer n such that k * n
≡ 1 mod modulus, and #f otherwise.
Returns an integer n such that 1 = (n * k2) mod modulus. If k2 has no inverse mod modulus an error is signaled.
Returns (-k2) mod modulus.
Returns (k2 + k3) mod modulus.
Returns (k2 - k3) mod modulus.
Returns (k2 * k3) mod modulus.
The Scheme code for modular:* with negative modulus is not
completed for fixnum-only implementations.
Returns (k2 ^ k3) mod modulus.
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A pseudo-random number generator is only as good as the tests it passes. George Marsaglia of Florida State University developed a battery of tests named DIEHARD (http://stat.fsu.edu/~geo/diehard.html). ‘diehard.c’ has a bug which the patch ftp://swissnet.ai.mit.edu/pub/users/jaffer/diehard.c.pat corrects.
SLIB’s new PRNG generates 8 bits at a time. With the degenerate seed ‘0’, the numbers generated pass DIEHARD; but when bits are combined from sequential bytes, tests fail. With the seed ‘http://swissnet.ai.mit.edu/~jaffer/SLIB.html’, all of those tests pass.
If inexact numbers are supported by the Scheme implementation, ‘randinex.scm’ will be loaded as well. ‘randinex.scm’ contains procedures for generating inexact distributions.
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Returns an expression for a procedure of one argument, a port. This procedure reads characters from the port until the end of file and returns the integer checksum of the bytes read.
The integer degree, if given, specifies the degree of the polynomial being computed – which is also the number of bits computed in the checksums. The default value is 32.
The integer generator specifies the polynomial being computed. The power of 2 generating each 1 bit is the exponent of a term of the polynomial. The bit at position degree is implicit and should not be part of generator. This allows systems with numbers limited to 32 bits to calculate 32 bit checksums. The default value of generator when degree is 32 (its default) is:
(make-port-crc 32 #b00000100110000010001110110110111)
Creates a procedure to calculate the P1003.2/D11.2 (POSIX.2) 32-bit checksum from the polynomial:
32 26 23 22 16 12 11
( x + x + x + x + x + x + x +
10 8 7 5 4 2 1
x + x + x + x + x + x + x + 1 ) mod 2
(require 'make-crc) (define crc32 (slib:eval (make-port-crc))) (define (file-check-sum file) (call-with-input-file file crc32)) (file-check-sum (in-vicinity (library-vicinity) "ratize.scm")) ⇒ 3553047446
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The plotting procedure is made available through the use of the
charplot package. charplot is loaded by inserting
(require 'charplot) before the code that uses this
procedure.
The number of rows to make the plot vertically.
The number of columns to make the plot horizontally.
coords is a list of pairs of x and y coordinates. x-label and y-label are strings with which to label the x and y axes.
Example:
(require 'charplot) (set! charplot:height 19) (set! charplot:width 45) (define (make-points n) (if (zero? n) '() (cons (cons (/ n 6) (sin (/ n 6))) (make-points (1- n))))) (plot! (make-points 37) "x" "Sin(x)") -|
Sin(x) ______________________________________________
1.25|- |
| |
1|- **** |
| ** ** |
750.0e-3|- * * |
| * * |
500.0e-3|- * * |
| * |
250.0e-3|- * |
| * * |
0|-------------------*--------------------------|
| * |
-250.0e-3|- * * |
| * * |
-500.0e-3|- * |
| * * |
-750.0e-3|- * * |
| ** ** |
-1|- **** |
|____________:_____._____:_____._____:_________|
x 2 4
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Given integer valued procedure f, its derivative (with respect to
its argument) df/dx, and initial integer value x0 for which
df/dx(x0) is non-zero, returns an integer x for which
f(x) is closer to zero than either of the integers adjacent
to x; or returns #f if such an integer can’t be found.
To find the closest integer to a given integers square root:
(define (integer-sqrt y) (newton:find-integer-root (lambda (x) (- (* x x) y)) (lambda (x) (* 2 x)) (ash 1 (quotient (integer-length y) 2)))) (integer-sqrt 15) ⇒ 4
Given a non-negative integer y, returns the rounded square-root of y.
Given real valued procedures f, df/dx of one (real)
argument, initial real value x0 for which df/dx(x0) is
non-zero, and positive real number prec, returns a real x
for which abs(f(x)) is less than prec; or
returns #f if such a real can’t be found.
If prec is instead a negative integer, newton:find-root
returns the result of -prec iterations.
H. J. Orchard, The Laguerre Method for Finding the Zeros of Polynomials, IEEE Transactions on Circuits and Systems, Vol. 36, No. 11, November 1989, pp 1377-1381.
There are 2 errors in Orchard’s Table II. Line k=2 for starting value of 1000+j0 should have Z_k of 1.0475 + j4.1036 and line k=2 for starting value of 0+j1000 should have Z_k of 1.0988 + j4.0833.
Given complex valued procedure f of one (complex) argument, its
derivative (with respect to its argument) df/dx, its second
derivative ddf/dz^2, initial complex value z0, and positive
real number prec, returns a complex number z for which
magnitude(f(z)) is less than prec; or returns
#f if such a number can’t be found.
If prec is instead a negative integer, laguerre:find-root
returns the result of -prec iterations.
Given polynomial procedure f of integer degree deg of one
argument, its derivative (with respect to its argument) df/dx, its
second derivative ddf/dz^2, initial complex value z0, and
positive real number prec, returns a complex number z for
which magnitude(f(z)) is less than prec; or
returns #f if such a number can’t be found.
If prec is instead a negative integer,
laguerre:find-polynomial-root returns the result of -prec
iterations.
Given a real valued procedure f and two real valued starting
points x0 and x1, returns a real x for which
(abs (f x)) is less than prec; or returns
#f if such a real can’t be found.
If x0 and x1 are chosen such that they bracket a root, that is
(or (< (f x0) 0 (f x1))
(< (f x1) 0 (f x0)))
then the root returned will be between x0 and x1, and f will not be passed an argument outside of that interval.
secant:find-bracketed-root will return #f unless x0
and x1 bracket a root.
The secant or regula falsi method will be used unless a bracketing interval has been found and the secant method is not making sufficient progress, in which case bisection of the interval will be used.
If prec is instead a negative integer, secant:find-root
returns the result of -prec iterations.
If prec is a procedure it should accept 5 arguments: x0
f0 x1 f1 and count, where f0 will be
(f x0), f1 (f x1), and count the number of
iterations performed so far. prec should return non-false
if the iteration should be stopped.
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Scheme provides a consistent and capable set of numeric functions. Inexacts implement a field; integers a commutative ring (and Euclidean domain). This package allows one to use basic Scheme numeric functions with symbols and non-numeric elements of commutative rings.
The commutative-ring package makes the procedures +,
-, *, /, and ^ careful in the sense
that any non-numeric arguments they do not reduce appear in the
expression output. In order to see what working with this package is
like, self-set all the single letter identifiers (to their corresponding
symbols).
(define a 'a) … (define z 'z)
Or just (require 'self-set). Now try some sample expressions:
(+ (+ a b) (- a b)) ⇒ (* a 2) (* (+ a b) (+ a b)) ⇒ (^ (+ a b) 2) (* (+ a b) (- a b)) ⇒ (* (+ a b) (- a b)) (* (- a b) (- a b)) ⇒ (^ (- a b) 2) (* (- a b) (+ a b)) ⇒ (* (+ a b) (- a b)) (/ (+ a b) (+ c d)) ⇒ (/ (+ a b) (+ c d)) (^ (+ a b) 3) ⇒ (^ (+ a b) 3) (^ (+ a 2) 3) ⇒ (^ (+ 2 a) 3)
Associative rules have been applied and repeated addition and multiplication converted to multiplication and exponentiation.
We can enable distributive rules, thus expanding to sum of products form:
(set! *ruleset* (combined-rulesets distribute* distribute/)) (* (+ a b) (+ a b)) ⇒ (+ (* 2 a b) (^ a 2) (^ b 2)) (* (+ a b) (- a b)) ⇒ (- (^ a 2) (^ b 2)) (* (- a b) (- a b)) ⇒ (- (+ (^ a 2) (^ b 2)) (* 2 a b)) (* (- a b) (+ a b)) ⇒ (- (^ a 2) (^ b 2)) (/ (+ a b) (+ c d)) ⇒ (+ (/ a (+ c d)) (/ b (+ c d))) (/ (+ a b) (- c d)) ⇒ (+ (/ a (- c d)) (/ b (- c d))) (/ (- a b) (- c d)) ⇒ (- (/ a (- c d)) (/ b (- c d))) (/ (- a b) (+ c d)) ⇒ (- (/ a (+ c d)) (/ b (+ c d))) (^ (+ a b) 3) ⇒ (+ (* 3 a (^ b 2)) (* 3 b (^ a 2)) (^ a 3) (^ b 3)) (^ (+ a 2) 3) ⇒ (+ 8 (* a 12) (* (^ a 2) 6) (^ a 3))
Use of this package is not restricted to simple arithmetic expressions:
(require 'determinant) (determinant '((a b c) (d e f) (g h i))) ⇒ (- (+ (* a e i) (* b f g) (* c d h)) (* a f h) (* b d i) (* c e g))
Currently, only +, -, *, /, and ^
support non-numeric elements. Expressions with - are converted
to equivalent expressions without -, so behavior for - is
not defined separately. / expressions are handled similarly.
This list might be extended to include quotient, modulo,
remainder, lcm, and gcd; but these work only for
the more restrictive Euclidean (Unique Factorization) Domain.
The commutative-ring package allows control of ring properties through the use of rulesets.
Contains the set of rules currently in effect. Rules defined by
cring:define-rule are stored within the value of *ruleset* at the
time cring:define-rule is called. If *ruleset* is
#f, then no rules apply.
Returns a new ruleset containing the rules formed by applying
cring:define-rule to each 4-element list argument rule. If
the first argument to make-ruleset is a symbol, then the database
table created for the new ruleset will be named name. Calling
make-ruleset with no rule arguments creates an empty ruleset.
Returns a new ruleset containing the rules contained in each ruleset
argument ruleset. If the first argument to
combined-ruleset is a symbol, then the database table created for
the new ruleset will be named name. Calling
combined-ruleset with no ruleset arguments creates an empty
ruleset.
Two rulesets are defined by this package.
Contain the ruleset to distribute multiplication over addition and subtraction.
Contain the ruleset to distribute division over addition and subtraction.
Take care when using both distribute* and distribute/
simultaneously. It is possible to put / into an infinite loop.
You can specify how sum and product expressions containing non-numeric
elements simplify by specifying the rules for + or * for
cases where expressions involving objects reduce to numbers or to
expressions involving different non-numeric elements.
Defines a rule for the case when the operation represented by symbol
op is applied to lists whose cars are sub-op1 and
sub-op2, respectively. The argument reduction is a
procedure accepting 2 arguments which will be lists whose cars
are sub-op1 and sub-op2.
Defines a rule for the case when the operation represented by symbol
op is applied to a list whose car is sub-op1, and
some other argument. Reduction will be called with the list whose
car is sub-op1 and some other argument.
If reduction returns #f, the reduction has failed and other
reductions will be tried. If reduction returns a non-false value,
that value will replace the two arguments in arithmetic (+,
-, and *) calculations involving non-numeric elements.
The operations + and * are assumed commutative; hence both
orders of arguments to reduction will be tried if necessary.
The following rule is the definition for distributing * over
+.
(cring:define-rule '* '+ 'identity (lambda (exp1 exp2) (apply + (map (lambda (trm) (* trm exp2)) (cdr exp1))))))
The first step in creating your commutative ring is to write procedures to create elements of the ring. A non-numeric element of the ring must be represented as a list whose first element is a symbol or string. This first element identifies the type of the object. A convenient and clear convention is to make the type-identifying element be the same symbol whose top-level value is the procedure to create it.
(define (n . list1)
(cond ((and (= 2 (length list1))
(eq? (car list1) (cadr list1)))
0)
((not (term< (first list1) (last1 list1)))
(apply n (reverse list1)))
(else (cons 'n list1))))
(define (s x y) (n x y))
(define (m . list1)
(cond ((neq? (first list1) (term_min list1))
(apply m (cyclicrotate list1)))
((term< (last1 list1) (cadr list1))
(apply m (reverse (cyclicrotate list1))))
(else (cons 'm list1))))
Define a procedure to multiply 2 non-numeric elements of the ring. Other multiplicatons are handled automatically. Objects for which rules have not been defined are not changed.
(define (n*n ni nj)
(let ((list1 (cdr ni)) (list2 (cdr nj)))
(cond ((null? (intersection list1 list2)) #f)
((and (eq? (last1 list1) (first list2))
(neq? (first list1) (last1 list2)))
(apply n (splice list1 list2)))
((and (eq? (first list1) (first list2))
(neq? (last1 list1) (last1 list2)))
(apply n (splice (reverse list1) list2)))
((and (eq? (last1 list1) (last1 list2))
(neq? (first list1) (first list2)))
(apply n (splice list1 (reverse list2))))
((and (eq? (last1 list1) (first list2))
(eq? (first list1) (last1 list2)))
(apply m (cyclicsplice list1 list2)))
((and (eq? (first list1) (first list2))
(eq? (last1 list1) (last1 list2)))
(apply m (cyclicsplice (reverse list1) list2)))
(else #f))))
Test the procedures to see if they work.
;;; where cyclicrotate(list) is cyclic rotation of the list one step
;;; by putting the first element at the end
(define (cyclicrotate list1)
(append (rest list1) (list (first list1))))
;;; and where term_min(list) is the element of the list which is
;;; first in the term ordering.
(define (term_min list1)
(car (sort list1 term<)))
(define (term< sym1 sym2)
(string<? (symbol->string sym1) (symbol->string sym2)))
(define first car)
(define rest cdr)
(define (last1 list1) (car (last-pair list1)))
(define (neq? obj1 obj2) (not (eq? obj1 obj2)))
;;; where splice is the concatenation of list1 and list2 except that their
;;; common element is not repeated.
(define (splice list1 list2)
(cond ((eq? (last1 list1) (first list2))
(append list1 (cdr list2)))
(else (error 'splice list1 list2))))
;;; where cyclicsplice is the result of leaving off the last element of
;;; splice(list1,list2).
(define (cyclicsplice list1 list2)
(cond ((and (eq? (last1 list1) (first list2))
(eq? (first list1) (last1 list2)))
(butlast (splice list1 list2) 1))
(else (error 'cyclicsplice list1 list2))))
(N*N (S a b) (S a b)) ⇒ (m a b)
Then register the rule for multiplying type N objects by type N objects.
(cring:define-rule '* 'N 'N N*N))
Now we are ready to compute!
(define (t)
(define detM
(+ (* (S g b)
(+ (* (S f d)
(- (* (S a f) (S d g)) (* (S a g) (S d f))))
(* (S f f)
(- (* (S a g) (S d d)) (* (S a d) (S d g))))
(* (S f g)
(- (* (S a d) (S d f)) (* (S a f) (S d d))))))
(* (S g d)
(+ (* (S f b)
(- (* (S a g) (S d f)) (* (S a f) (S d g))))
(* (S f f)
(- (* (S a b) (S d g)) (* (S a g) (S d b))))
(* (S f g)
(- (* (S a f) (S d b)) (* (S a b) (S d f))))))
(* (S g f)
(+ (* (S f b)
(- (* (S a d) (S d g)) (* (S a g) (S d d))))
(* (S f d)
(- (* (S a g) (S d b)) (* (S a b) (S d g))))
(* (S f g)
(- (* (S a b) (S d d)) (* (S a d) (S d b))))))
(* (S g g)
(+ (* (S f b)
(- (* (S a f) (S d d)) (* (S a d) (S d f))))
(* (S f d)
(- (* (S a b) (S d f)) (* (S a f) (S d b))))
(* (S f f)
(- (* (S a d) (S d b)) (* (S a b) (S d d))))))))
(* (S b e) (S c a) (S e c)
detM
))
(pretty-print (t))
-|
(- (+ (m a c e b d f g)
(m a c e b d g f)
(m a c e b f d g)
(m a c e b f g d)
(m a c e b g d f)
(m a c e b g f d))
(* 2 (m a b e c) (m d f g))
(* (m a c e b d) (m f g))
(* (m a c e b f) (m d g))
(* (m a c e b g) (m d f)))
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(require 'determinant) (determinant '((1 2) (3 4))) ⇒ -2 (determinant '((1 2 3) (4 5 6) (7 8 9))) ⇒ 0 (determinant '((1 2 3 4) (5 6 7 8) (9 10 11 12))) ⇒ 0
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| 5.1 Base Table | ||
| 5.2 Relational Database | ’relational-database | |
| 5.3 Weight-Balanced Trees | ’wt-tree |
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A base table implementation using Scheme association lists is available
as the value of the identifier alist-table after doing:
Association list base tables are suitable for small databases and support all Scheme types when temporary and readable/writeable Scheme types when saved. I hope support for other base table implementations will be added in the future.
This rest of this section documents the interface for a base table implementation from which the Relational Database package constructs a Relational system. It will be of interest primarily to those wishing to port or write new base-table implementations.
All of these functions are accessed through a single procedure by
calling that procedure with the symbol name of the operation. A
procedure will be returned if that operation is supported and #f
otherwise. For example:
(require 'alist-table) (define open-base (alist-table 'make-base)) make-base ⇒ *a procedure* (define foo (alist-table 'foo)) foo ⇒ #f
Returns a new, open, low-level database (collection of tables)
associated with filename. This returned database has an empty
table associated with catalog-id. The positive integer
key-dimension is the number of keys composed to make a
primary-key for the catalog table. The list of symbols
column-types describes the types of each column for that table.
If the database cannot be created as specified, #f is returned.
Calling the close-base method on this database and possibly other
operations will cause filename to be written to. If
filename is #f a temporary, non-disk based database will be
created if such can be supported by the base table implelentation.
Returns an open low-level database associated with filename. If
mutable? is #t, this database will have methods capable of
effecting change to the database. If mutable? is #f, only
methods for inquiring the database will be available. If the database
cannot be opened as specified #f is returned.
Calling the close-base (and possibly other) method on a
mutable? database will cause filename to be written to.
Causes the low-level database lldb to be written to
filename. If the write is successful, also causes lldb to
henceforth be associated with filename. Calling the
close-database (and possibly other) method on lldb may
cause filename to be written to. If filename is #f
this database will be changed to a temporary, non-disk based database if
such can be supported by the underlying base table implelentation. If
the operations completed successfully, #t is returned.
Otherwise, #f is returned.
Causes the file associated with the low-level database lldb to be
updated to reflect its current state. If the associated filename is
#f, no action is taken and #f is returned. If this
operation completes successfully, #t is returned. Otherwise,
#f is returned.
Causes the low-level database lldb to be written to its associated
file (if any). If the write is successful, subsequent operations to
lldb will signal an error. If the operations complete
successfully, #t is returned. Otherwise, #f is returned.
Returns the base-id for a new base table, otherwise returns
#f. The base table can then be opened using (open-table
lldb base-id). The positive integer key-dimension is
the number of keys composed to make a primary-key for this table.
The list of symbols column-types describes the types of each
column.
A constant base-id suitable for passing as a parameter to
open-table. catalog-id will be used as the base table for
the system catalog.
Returns a handle for an existing base table in the low-level
database lldb if that table exists and can be opened in the mode
indicated by mutable?, otherwise returns #f.
As with make-table, the positive integer key-dimension is
the number of keys composed to make a primary-key for this table.
The list of symbols column-types describes the types of each
column.
Returns #t if the base table associated with base-id was
removed from the low level database lldb, and #f otherwise.
Returns a procedure which accepts a single argument which must be of type type. This returned procedure returns an object suitable for being a key argument in the functions whose descriptions follow.
Any 2 arguments of the supported type passed to the returned function
which are not equal? must result in returned values which are not
equal?.
The list of symbols types must have at least key-dimension elements. Returns a procedure which accepts a list of length key-dimension and whose types must corresopond to the types named by types. This returned procedure combines the elements of its list argument into an object suitable for being a key argument in the functions whose descriptions follow.
Any 2 lists of supported types (which must at least include symbols and
non-negative integers) passed to the returned function which are not
equal? must result in returned values which are not
equal?.
Returns a procedure which accepts objects produced by application of the
result of (make-list-keyifier key-dimension types).
This procedure returns a key which is equal? to the
column-numberth element of the list which was passed to create
combined-key. The list types must have at least
key-dimension elements.
Returns a procedure which accepts objects produced by application of the
result of (make-list-keyifier key-dimension types).
This procedure returns a list of keys which are elementwise
equal? to the list which was passed to create combined-key.
In the following functions, the key argument can always be assumed to be the value returned by a call to a keyify routine.
In contrast, a match-key argument is a list of length equal to the number of primary keys. The match-key restricts the actions of the table command to those records whose primary keys all satisfy the corresponding element of the match-key list. The elements and their actions are:
#fThe false value matches any key in the corresponding position.
- an object of type procedure
This procedure must take a single argument, the key in the corresponding position. Any key for which the procedure returns a non-false value is a match; Any key for which the procedure returns a
#fis not.- other values
Any other value matches only those keys
equal?to it.
Calls procedure once with each key in the table opened in handle which satisfies match-key in an unspecified order. An unspecified value is returned.
Returns a list of the values returned by calling procedure once with each key in the table opened in handle which satisfies match-key in an unspecified order.
Calls procedure once with each key in the table opened in handle which satisfies match-key in the natural order for the types of the primary key fields of that table. An unspecified value is returned.
Removes all rows which satisfy match-key from the table opened in handle. An unspecified value is returned.
Returns a non-#f value if there is a row associated with
key in the table opened in handle and #f otherwise.
Removes the row associated with key from the table opened in handle. An unspecified value is returned.
Returns a procedure which takes arguments handle and key.
This procedure returns a list of the non-primary values of the relation
(in the base table opened in handle) whose primary key is
key if it exists, and #f otherwise.
Returns a procedure which takes arguments handle and key and value-list. This procedure associates the primary key key with the values in value-list (in the base table opened in handle) and returns an unspecified value.
Returns #t if symbol names a type allowed as a column value
by the implementation, and #f otherwise. At a minimum, an
implementation must support the types integer, symbol,
string, boolean, and base-id.
Returns #t if symbol names a type allowed as a key value by
the implementation, and #f otherwise. At a minimum, an
implementation must support the types integer, and symbol.
integerScheme exact integer.
symbolScheme symbol.
boolean#t or #f.
base-idObjects suitable for passing as the base-id parameter to
open-table. The value of catalog-id must be an acceptable
base-id.
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(require 'relational-database)
This package implements a database system inspired by the Relational Model (E. F. Codd, A Relational Model of Data for Large Shared Data Banks). An SLIB relational database implementation can be created from any Base Table implementation.
| 5.2.1 Motivations | Database Manifesto | |
| 5.2.2 Creating and Opening Relational Databases | ||
| 5.2.3 Relational Database Operations | ||
| 5.2.4 Table Operations | ||
| 5.2.5 Catalog Representation | ||
| 5.2.6 Unresolved Issues | ||
| 5.2.7 Database Utilities | ’database-utilities | |
| 5.2.8 Database Reports | ||
| 5.2.9 Database Browser | ’database-browse |
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Most nontrivial programs contain databases: Makefiles, configure scripts, file backup, calendars, editors, source revision control, CAD systems, display managers, menu GUIs, games, parsers, debuggers, profilers, and even error reporting are all rife with databases. Coding databases is such a common activity in programming that many may not be aware of how often they do it.
A database often starts as a dispatch in a program. The author, perhaps because of the need to make the dispatch configurable, the need for correlating dispatch in other routines, or because of changes or growth, devises a data structure to contain the information, a routine for interpreting that data structure, and perhaps routines for augmenting and modifying the stored data. The dispatch must be converted into this form and tested.
The programmer may need to devise an interactive program for enabling easy examination and modification of the information contained in this database. Often, in an attempt to foster modularity and avoid delays in release, intermediate file formats for the database information are devised. It often turns out that users prefer modifying these intermediate files with a text editor to using the interactive program in order to do operations (such as global changes) not forseen by the program’s author.
In order to address this need, the conscientious software engineer may even provide a scripting language to allow users to make repetitive database changes. Users will grumble that they need to read a large manual and learn yet another programming language (even if it almost has language "xyz" syntax) in order to do simple configuration.
All of these facilities need to be designed, coded, debugged, documented, and supported; often causing what was very simple in concept to become a major developement project.
This view of databases just outlined is somewhat the reverse of the view of the originators of the Relational Model of database abstraction. The relational model was devised to unify and allow interoperation of large multi-user databases running on diverse platforms. A fairly general purpose "Comprehensive Language" for database manipulations is mandated (but not specified) as part of the relational model for databases.
One aspect of the Relational Model of some importance is that the "Comprehensive Language" must be expressible in some form which can be stored in the database. This frees the programmer from having to make programs data-driven in order to use a database.
This package includes as one of its basic supported types Scheme
expressions. This type allows expressions as defined by the
Scheme standards to be stored in the database. Using slib:eval
retrieved expressions can be evaluated (in the top-level environment).
Scheme’s lambda facilitates closure of environments, modularity,
etc. so that procedures (which could not be stored directly most
databases) can still be effectively retrieved. Since slib:eval
evaluates expressions in the top-level environment, built-in and user
defined procedures can be easily accessed by name.
This package’s purpose is to standardize (through a common interface) database creation and usage in Scheme programs. The relational model’s provision for inclusion of language expressions as data as well as the description (in tables, of course) of all of its tables assures that relational databases are powerful enough to assume the roles currently played by thousands of ad-hoc routines and data formats.
Such standardization to a relational-like model brings many benefits:
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Returns a procedure implementing a relational database using the base-table-implementation.
All of the operations of a base table implementation are accessed
through a procedure defined by requireing that implementation.
Similarly, all of the operations of the relational database
implementation are accessed through the procedure returned by
make-relational-system. For instance, a new relational database
could be created from the procedure returned by
make-relational-system by:
What follows are the descriptions of the methods available from
relational system returned by a call to make-relational-system.
Returns an open, nearly empty relational database associated with
filename. The only tables defined are the system catalog and
domain table. Calling the close-database method on this database
and possibly other operations will cause filename to be written
to. If filename is #f a temporary, non-disk based database
will be created if such can be supported by the underlying base table
implelentation. If the database cannot be created as specified
#f is returned. For the fields and layout of descriptor tables,
See section Catalog Representation
Returns an open relational database associated with filename. If
mutable? is #t, this database will have methods capable of
effecting change to the database. If mutable? is #f, only
methods for inquiring the database will be available. Calling the
close-database (and possibly other) method on a mutable?
database will cause filename to be written to. If the database
cannot be opened as specified #f is returned.
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These are the descriptions of the methods available from an open relational database. A method is retrieved from a database by calling the database with the symbol name of the operation. For example:
(define my-database
(create-alist-database "mydata.db"))
(define telephone-table-desc
((my-database 'create-table) 'telephone-table-desc))
Causes the relational database to be written to its associated file (if
any). If the write is successful, subsequent operations to this
database will signal an error. If the operations completed
successfully, #t is returned. Otherwise, #f is returned.
Causes the relational database to be written to filename. If the
write is successful, also causes the database to henceforth be
associated with filename. Calling the close-database (and
possibly other) method on this database will cause filename to be
written to. If filename is #f this database will be
changed to a temporary, non-disk based database if such can be supported
by the underlying base table implelentation. If the operations
completed successfully, #t is returned. Otherwise, #f is
returned.
Returns #t if table-name exists in the system catalog,
otherwise returns #f.
Returns a methods procedure for an existing relational table in
this database if it exists and can be opened in the mode indicated by
mutable?, otherwise returns #f.
These methods will be present only in databases which are mutable?.
Removes and returns the table-name row from the system catalog if
the table or view associated with table-name gets removed from the
database, and #f otherwise.
Returns a methods procedure for a new (open) relational table for
describing the columns of a new base table in this database, otherwise
returns #f. For the fields and layout of descriptor tables,
See section Catalog Representation.
Returns a methods procedure for a new (open) relational table with
columns as described by table-desc-name, otherwise returns
#f.
Not yet implemented.
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These are the descriptions of the methods available from an open relational table. A method is retrieved from a table by calling the table with the symbol name of the operation. For example:
(define telephone-table-desc
((my-database 'create-table) 'telephone-table-desc))
(require 'common-list-functions)
(define ndrp (telephone-table-desc 'row:insert))
(ndrp '(1 #t name #f string))
(ndrp '(2 #f telephone
(lambda (d)
(and (string? d) (> (string-length d) 2)
(every
(lambda (c)
(memv c '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
#\+ #\( #\ #\) #\-)))
(string->list d))))
string))
Some operations described below require primary key arguments. Primary keys arguments are denoted key1 key2 …. It is an error to call an operation for a table which takes primary key arguments with the wrong number of primary keys for that table.
The term row used below refers to a Scheme list of values (one for
each column) in the order specified in the descriptor (table) for this
table. Missing values appear as #f. Primary keys must not
be missing.
Returns a procedure of arguments key1 key2 … which
returns the value for the column-name column of the row associated
with primary keys key1, key2 … if that row exists in
the table, or #f otherwise.
((plat 'get 'processor) 'djgpp) ⇒ i386 ((plat 'get 'processor) 'be-os) ⇒ #f
Returns a procedure of optional arguments match-key1 … which returns a list of the values for the specified column for all rows in this table. The optional match-key1 … arguments restrict actions to a subset of the table. See the match-key description below for details.
((plat 'get* 'processor)) ⇒ (i386 8086 i386 8086 i386 i386 8086 m68000 m68000 m68000 m68000 m68000 powerpc) ((plat 'get* 'processor) #f) ⇒ (i386 8086 i386 8086 i386 i386 8086 m68000 m68000 m68000 m68000 m68000 powerpc) (define (a-key? key) (char=? #\a (string-ref (symbol->string key) 0))) ((plat 'get* 'processor) a-key?) ⇒ (m68000 m68000 m68000 m68000 m68000 powerpc) ((plat 'get* 'name) a-key?) ⇒ (atari-st-turbo-c atari-st-gcc amiga-sas/c-5.10 amiga-aztec amiga-dice-c aix)
Returns a procedure of arguments key1 key2 … which
returns the row associated with primary keys key1, key2
… if it exists, or #f otherwise.
((plat 'row:retrieve) 'linux) ⇒ (linux i386 linux gcc) ((plat 'row:retrieve) 'multics) ⇒ #f
Returns a procedure of optional arguments match-key1 … which returns a list of all rows in this table. The optional match-key1 … arguments restrict actions to a subset of the table. See the match-key description below for details.
((plat 'row:retrieve*) a-key?) ⇒ ((atari-st-turbo-c m68000 atari turbo-c) (atari-st-gcc m68000 atari gcc) (amiga-sas/c-5.10 m68000 amiga sas/c) (amiga-aztec m68000 amiga aztec) (amiga-dice-c m68000 amiga dice-c) (aix powerpc aix -))
Returns a procedure of arguments key1 key2 … which
removes and returns the row associated with primary keys key1,
key2 … if it exists, or #f otherwise.
Returns a procedure of optional arguments match-key1 … which removes and returns a list of all rows in this table. The optional match-key1 … arguments restrict actions to a subset of the table. See the match-key description below for details.
Returns a procedure of arguments key1 key2 … which deletes the row associated with primary keys key1, key2 … if it exists. The value returned is unspecified.
Returns a procedure of optional arguments match-key1 … which Deletes all rows from this table. The optional match-key1 … arguments restrict deletions to a subset of the table. See the match-key description below for details. The value returned is unspecified. The descriptor table and catalog entry for this table are not affected.
Returns a procedure of one argument, row, which adds the row, row, to this table. If a row for the primary key(s) specified by row already exists in this table, it will be overwritten. The value returned is unspecified.
Returns a procedure of one argument, rows, which adds each row in the list of rows, rows, to this table. If a row for the primary key specified by an element of rows already exists in this table, it will be overwritten. The value returned is unspecified.
Adds the row row to this table. If a row for the primary key(s) specified by row already exists in this table an error is signaled. The value returned is unspecified.
Returns a procedure of one argument, rows, which adds each row in the list of rows, rows, to this table. If a row for the primary key specified by an element of rows already exists in this table, an error is signaled. The value returned is unspecified.
Returns a procedure of arguments proc match-key1 … which calls proc with each row in this table in the (implementation-dependent) natural ordering for rows. The optional match-key1 … arguments restrict actions to a subset of the table. See the match-key description below for details.
Real relational programmers would use some least-upper-bound join for every row to get them in order; But we don’t have joins yet.
The (optional) match-key1 … arguments are used to restrict
actions of a whole-table operation to a subset of that table. Those
procedures (returned by methods) which accept match-key arguments will
accept any number of match-key arguments between zero and the number of
primary keys in the table. Any unspecified match-key arguments
default to #f.
The match-key1 … restrict the actions of the table command to those records whose primary keys each satisfy the corresponding match-key argument. The arguments and their actions are:
#fThe false value matches any key in the corresponding position.
- an object of type procedure
This procedure must take a single argument, the key in the corresponding position. Any key for which the procedure returns a non-false value is a match; Any key for which the procedure returns a
#fis not.- other values
Any other value matches only those keys
equal?to it.
Subsequent operations to this table will signal an error.
Return a list of the column names, foreign-key table names, domain names, or type names respectively for this table. These 4 methods are different from the others in that the list is returned, rather than a procedure to obtain the list.
Returns the number of primary keys fields in the relations in this table.
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Each database (in an implementation) has a system catalog which describes all the user accessible tables in that database (including itself).
The system catalog base table has the following fields. PRI
indicates a primary key for that table.
PRI table-name
column-limit the highest column number
coltab-name descriptor table name
bastab-id data base table identifier
user-integrity-rule
view-procedure A scheme thunk which, when called,
produces a handle for the view. coltab
and bastab are specified if and only if
view-procedure is not.
Descriptors for base tables (not views) are tables (pointed to by system catalog). Descriptor (base) tables have the fields:
PRI column-number sequential integers from 1
primary-key? boolean TRUE for primary key components
column-name
column-integrity-rule
domain-name
A primary key is any column marked as primary-key? in the
corresponding descriptor table. All the primary-key? columns
must have lower column numbers than any non-primary-key? columns.
Every table must have at least one primary key. Primary keys must be
sufficient to distinguish all rows from each other in the table. All of
the system defined tables have a single primary key.
This package currently supports tables having from 1 to 4 primary keys if there are non-primary columns, and any (natural) number if all columns are primary keys. If you need more than 4 primary keys, I would like to hear what you are doing!
A domain is a category describing the allowable values to occur in a column. It is described by a (base) table with the fields:
PRI domain-name
foreign-table
domain-integrity-rule
type-id
type-param
The type-id field value is a symbol. This symbol may be used by the underlying base table implementation in storing that field.
If the foreign-table field is non-#f then that field names
a table from the catalog. The values for that domain must match a
primary key of the table referenced by the type-param (or
#f, if allowed). This package currently does not support
composite foreign-keys.
The types for which support is planned are:
atom
symbol
string [<length>]
number [<base>]
money <currency>
date-time
boolean
foreign-key <table-name>
expression
virtual <expression>
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Although ‘rdms.scm’ is not large, I found it very difficult to write (six rewrites). I am not aware of any other examples of a generalized relational system (although there is little new in CS). I left out several aspects of the Relational model in order to simplify the job. The major features lacking (which might be addressed portably) are views, transaction boundaries, and protection.
Protection needs a model for specifying priveledges. Given how operations are accessed from handles it should not be difficult to restrict table accesses to those allowed for that user.
The system catalog has a field called view-procedure. This
should allow a purely functional implementation of views. This will
work but is unsatisfying for views resulting from a selection
(subset of rows); for whole table operations it will not be possible to
reduce the number of keys scanned over when the selection is specified
only by an opaque procedure.
Transaction boundaries present the most intriguing area. Transaction boundaries are actually a feature of the "Comprehensive Language" of the Relational database and not of the database. Scheme would seem to provide the opportunity for an extremely clean semantics for transaction boundaries since the builtin procedures with side effects are small in number and easily identified.
These side-effect builtin procedures might all be portably redefined to versions which properly handled transactions. Compiled library routines would need to be recompiled as well. Many system extensions (delete-file, system, etc.) would also need to be redefined.
There are 2 scope issues that must be resolved for multiprocess transaction boundaries:
The actions captured by a transaction should be only for the process
which invoked the start of transaction. Although standard Scheme does
not provide process primitives as such, dynamic-wind would
provide a workable hook into process switching for many implementations.
Some shared utilities have state which should not be part of a transaction. An example would be calling a pseudo-random number generator. If the success of a transaction depended on the pseudo-random number and failed, the state of the generator would be set back. Subsequent calls would keep returning the same number and keep failing.
Pseudo-random number generators are not reentrant; thus they would require locks in order to operate properly in a multiprocess environment. Are all examples of utilities whose state should not be part of transactions also non-reentrant? If so, perhaps suspending transaction capture for the duration of locks would solve this problem.
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This enhancement wraps a utility layer on relational-database
which provides:
*commands*
table in database.
Also included are utilities which provide:
for any SLIB relational database.
Returns an open, nearly empty enhanced (with *commands* table)
relational database (with base-table type base-table-type)
associated with filename.
Returns an open enchanced relational database associated with
filename. The database will be opened with base-table type
base-table-type) if supplied. If base-table-type is not
supplied, open-database will attempt to deduce the correct
base-table-type. If the database can not be opened or if it lacks the
*commands* table, #f is returned.
Returns mutable open enchanced relational database …
The table *commands* in an enhanced relational-database has
the fields (with domains):
PRI name symbol
parameters parameter-list
procedure expression
documentation string
The parameters field is a foreign key (domain
parameter-list) of the *catalog-data* table and should
have the value of a table described by *parameter-columns*. This
parameter-list table describes the arguments suitable for passing
to the associated command. The intent of this table is to be of a form
such that different user-interfaces (for instance, pull-down menus or
plain-text queries) can operate from the same table. A
parameter-list table has the following fields:
PRI index uint
name symbol
arity parameter-arity
domain domain
defaulter expression
expander expression
documentation string
The arity field can take the values:
singleRequires a single parameter of the specified domain.
optionalA single parameter of the specified domain or zero parameters is acceptable.
booleanA single boolean parameter or zero parameters (in which case #f
is substituted) is acceptable.
naryAny number of parameters of the specified domain are acceptable. The argument passed to the command function is always a list of the parameters.
nary1One or more of parameters of the specified domain are acceptable. The argument passed to the command function is always a list of the parameters.
The domain field specifies the domain which a parameter or
parameters in the indexth field must satisfy.
The defaulter field is an expression whose value is either
#f or a procedure of one argument (the parameter-list) which
returns a list of the default value or values as appropriate.
Note that since the defaulter procedure is called every time a
default parameter is needed for this column, sticky defaults can
be implemented using shared state with the domain-integrity-rule.
When an enhanced relational-database is called with a symbol which
matches a name in the *commands* table, the associated
procedure expression is evaluated and applied to the enhanced
relational-database. A procedure should then be returned which the user
can invoke on (optional) arguments.
The command *initialize* is special. If present in the
*commands* table, open-database or open-database!
will return the value of the *initialize* command. Notice that
arbitrary code can be run when the *initialize* procedure is
automatically applied to the enhanced relational-database.
Note also that if you wish to shadow or hide from the user
relational-database methods described in Relational Database Operations, this can be done by a dispatch in the closure returned by
the *initialize* expression rather than by entries in the
*commands* table if it is desired that the underlying methods
remain accessible to code in the *commands* table.
Returns a procedure of 2 arguments, a (symbol) command and a call-back procedure. When this returned procedure is called, it looks up command in table table-name and calls the call-back procedure with arguments:
The command
The result of evaluating the expression in the procedure field of table-name and calling it with rdb.
A list of the official name of each parameter. Corresponds to the
name field of the command’s parameter-table.
A list of the positive integer index of each parameter. Corresponds to
the index field of the command’s parameter-table.
A list of the arities of each parameter. Corresponds to the
arity field of the command’s parameter-table. For a
description of arity see table above.
A list of the type name of each parameter. Correspnds to the
type-id field of the contents of the domain of the
command’s parameter-table.
A list of the defaulters for each parameter. Corresponds to
the defaulters field of the command’s parameter-table.
A list of procedures (one for each parameter) which tests whether a
value for a parameter is acceptable for that parameter. The procedure
should be called with each datum in the list for nary arity
parameters.
A list of lists of (alias parameter-name). There can be
more than one alias per parameter-name.
For information about parameters, See section Parameter lists. Here is an
example of setting up a command with arguments and parsing those
arguments from a getopt style argument list (see section Getopt).
(require 'database-utilities) (require 'fluid-let) (require 'parameters) (require 'getopt) (define my-rdb (create-database #f 'alist-table)) (define-tables my-rdb '(foo-params *parameter-columns* *parameter-columns* ((1 single-string single string (lambda (pl) '("str")) #f "single string") (2 nary-symbols nary symbol (lambda (pl) '()) #f "zero or more symbols") (3 nary1-symbols nary1 symbol (lambda (pl) '(symb)) #f "one or more symbols") (4 optional-number optional uint (lambda (pl) '()) #f "zero or one number") (5 flag boolean boolean (lambda (pl) '(#f)) #f "a boolean flag"))) '(foo-pnames ((name string)) ((parameter-index uint)) (("s" 1) ("single-string" 1) ("n" 2) ("nary-symbols" 2) ("N" 3) ("nary1-symbols" 3) ("o" 4) ("optional-number" 4) ("f" 5) ("flag" 5))) '(my-commands ((name symbol)) ((parameters parameter-list) (parameter-names parameter-name-translation) (procedure expression) (documentation string)) ((foo foo-params foo-pnames (lambda (rdb) (lambda args (print args))) "test command arguments")))) (define (dbutil:serve-command-line rdb command-table command argc argv) (set! argv (if (vector? argv) (vector->list argv) argv)) ((make-command-server rdb command-table) command (lambda (comname comval options positions arities types defaulters dirs aliases) (apply comval (getopt->arglist argc argv options positions arities types defaulters dirs aliases))))) (define (cmd . opts) (fluid-let ((*optind* 1)) (printf "%-34s ⇒ " (call-with-output-string (lambda (pt) (write (cons 'cmd opts) pt)))) (set! opts (cons "cmd" opts)) (force-output) (dbutil:serve-command-line my-rdb 'my-commands 'foo (length opts) opts))) (cmd) ⇒ ("str" () (symb) () #f) (cmd "-f") ⇒ ("str" () (symb) () #t) (cmd "--flag") ⇒ ("str" () (symb) () #t) (cmd "-o177") ⇒ ("str" () (symb) (177) #f) (cmd "-o" "177") ⇒ ("str" () (symb) (177) #f) (cmd "--optional" "621") ⇒ ("str" () (symb) (621) #f) (cmd "--optional=621") ⇒ ("str" () (symb) (621) #f) (cmd "-s" "speciality") ⇒ ("speciality" () (symb) () #f) (cmd "-sspeciality") ⇒ ("speciality" () (symb) () #f) (cmd "--single" "serendipity") ⇒ ("serendipity" () (symb) () #f) (cmd "--single=serendipity") ⇒ ("serendipity" () (symb) () #f) (cmd "-n" "gravity" "piety") ⇒ ("str" () (piety gravity) () #f) (cmd "-ngravity" "piety") ⇒ ("str" () (piety gravity) () #f) (cmd "--nary" "chastity") ⇒ ("str" () (chastity) () #f) (cmd "--nary=chastity" "") ⇒ ("str" () ( chastity) () #f) (cmd "-N" "calamity") ⇒ ("str" () (calamity) () #f) (cmd "-Ncalamity") ⇒ ("str" () (calamity) () #f) (cmd "--nary1" "surety") ⇒ ("str" () (surety) () #f) (cmd "--nary1=surety") ⇒ ("str" () (surety) () #f) (cmd "-N" "levity" "fealty") ⇒ ("str" () (fealty levity) () #f) (cmd "-Nlevity" "fealty") ⇒ ("str" () (fealty levity) () #f) (cmd "--nary1" "surety" "brevity") ⇒ ("str" () (brevity surety) () #f) (cmd "--nary1=surety" "brevity") ⇒ ("str" () (brevity surety) () #f) (cmd "-?") -| Usage: cmd [OPTION ARGUMENT ...] ... -f, --flag -o, --optional[=]<number> -n, --nary[=]<symbols> ... -N, --nary1[=]<symbols> ... -s, --single[=]<string> ERROR: getopt->parameter-list "unrecognized option" "-?"
Some commands are defined in all extended relational-databases. The are called just like Relational Database Operations.
Adds domain-row to the domains table if there is no row in
the domains table associated with key (car domain-row) and
returns #t. Otherwise returns #f.
For the fields and layout of the domain table, See section Catalog Representation. Currently, these fields are
The following example adds 3 domains to the ‘build’ database.
‘Optstring’ is either a string or #f. filename is a
string and build-whats is a symbol.
(for-each (build 'add-domain)
'((optstring #f
(lambda (x) (or (not x) (string? x)))
string
#f)
(filename #f #f string #f)
(build-whats #f #f symbol #f)))
Removes and returns the domain-name row from the domains table.
Returns a procedure to check an argument for conformance to domain domain.
Adds tables as specified in spec-0 … to the open relational-database rdb. Each spec has the form:
(<name> <descriptor-name> <descriptor-name> <rows>)
or
(<name> <primary-key-fields> <other-fields> <rows>)
where <name> is the table name, <descriptor-name> is the symbol name of a descriptor table, <primary-key-fields> and <other-fields> describe the primary keys and other fields respectively, and <rows> is a list of data rows to be added to the table.
<primary-key-fields> and <other-fields> are lists of field descriptors of the form:
(<column-name> <domain>)
or
(<column-name> <domain> <column-integrity-rule>)
where <column-name> is the column name, <domain> is the domain
of the column, and <column-integrity-rule> is an expression whose
value is a procedure of one argument (which returns #f to signal
an error).
If <domain> is not a defined domain name and it matches the name of this table or an already defined (in one of spec-0 …) single key field table, a foriegn-key domain will be created for it.
The following example shows a new database with the name of ‘foo.db’ being created with tables describing processor families and processor/os/compiler combinations.
The database command define-tables is defined to call
define-tables with its arguments. The database is also
configured to print ‘Welcome’ when the database is opened. The
database is then closed and reopened.
(require 'database-utilities) (define my-rdb (create-database "foo.db" 'alist-table)) (define-tables my-rdb '(*commands* ((name symbol)) ((parameters parameter-list) (procedure expression) (documentation string)) ((define-tables no-parameters no-parameter-names (lambda (rdb) (lambda specs (apply define-tables rdb specs))) "Create or Augment tables from list of specs") (*initialize* no-parameters no-parameter-names (lambda (rdb) (display "Welcome") (newline) rdb) "Print Welcome")))) ((my-rdb 'define-tables) '(processor-family ((family atom)) ((also-ran processor-family)) ((m68000 #f) (m68030 m68000) (i386 8086) (8086 #f) (powerpc #f))) '(platform ((name symbol)) ((processor processor-family) (os symbol) (compiler symbol)) ((aix powerpc aix -) (amiga-dice-c m68000 amiga dice-c) (amiga-aztec m68000 amiga aztec) (amiga-sas/c-5.10 m68000 amiga sas/c) (atari-st-gcc m68000 atari gcc) (atari-st-turbo-c m68000 atari turbo-c) (borland-c-3.1 8086 ms-dos borland-c) (djgpp i386 ms-dos gcc) (linux i386 linux gcc) (microsoft-c 8086 ms-dos microsoft-c) (os/2-emx i386 os/2 gcc) (turbo-c-2 8086 ms-dos turbo-c) (watcom-9.0 i386 ms-dos watcom)))) ((my-rdb 'close-database)) (set! my-rdb (open-database "foo.db" 'alist-table)) -| Welcome
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Code for generating database reports is in ‘report.scm’. After
writing it using format, I discovered that Common-Lisp
format is not useable for this application because there is no
mechanismm for truncating fields. ‘report.scm’ needs to be
rewritten using printf.
The symbol report-name must be primary key in the table named
*reports* in the relational database rdb.
destination is a port, string, or symbol. If destination is
a:
The table is created as ascii text and written to that port.
The table is created as ascii text and written to the file named by destination.
destination is the primary key for a row in the table named *printers*.
The report is prepared as follows:
Format (see section Format (version 3.0)) is called with the header field
and the (list of) column-names of the table.
Format is called with the reporter field and (on
successive calls) each record in the natural order for the table. A
count is kept of the number of newlines output by format. When the
number of newlines to be output exceeds the number of lines per page,
the set of lines will be broken if there are more than
minimum-break left on this page and the number of lines for this
row is larger or equal to twice minimum-break.
Format is called with the footer field and the (list of)
column-names of the table. The footer field should not output a
newline.
Each row in the table *reports* has the fields:
The report name.
The table to report on if none is specified.
A format string. At the beginning and end of each page
respectively, format is called with this string and the (list of)
column-names of this table.
A format string. For each row in the table, format is
called with this string and the row.
The minimum number of lines into which the report lines for a row can be
broken. Use 0 if a row’s lines should not be broken over page
boundaries.
Each row in the table *printers* has the fields:
The printer name.
The procedure to call to actually print.
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(require ’database-browse)
Prints the names of all the tables in database and sets browse’s default to database.
Prints the names of all the tables in the default database.
For each record of the table named by the symbol table-name, prints a line composed of all the field values.
Opens the database named by the string pathname, prints the names of all its tables, and sets browse’s default to the database.
Sets browse’s default to database and prints the records of the table named by the symbol table-name.
Opens the database named by the string pathname and sets browse’s
default to it; browse prints the records of the table named by
the symbol table-name.
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Balanced binary trees are a useful data structure for maintaining large sets of ordered objects or sets of associations whose keys are ordered. MIT Scheme has an comprehensive implementation of weight-balanced binary trees which has several advantages over the other data structures for large aggregates:
(+ 1 x)
modifies neither the constant 1 nor the value bound to x. The
trees are referentially transparent thus the programmer need not worry
about copying the trees. Referential transparency allows space
efficiency to be achieved by sharing subtrees.
These features make weight-balanced trees suitable for a wide range of applications, especially those that require large numbers of sets or discrete maps. Applications that have a few global databases and/or concentrate on element-level operations like insertion and lookup are probably better off using hash-tables or red-black trees.
The size of a tree is the number of associations that it contains. Weight balanced binary trees are balanced to keep the sizes of the subtrees of each node within a constant factor of each other. This ensures logarithmic times for single-path operations (like lookup and insertion). A weight balanced tree takes space that is proportional to the number of associations in the tree. For the current implementation, the constant of proportionality is six words per association.
Weight balanced trees can be used as an implementation for either
discrete sets or discrete maps (associations). Sets are implemented by
ignoring the datum that is associated with the key. Under this scheme
if an associations exists in the tree this indicates that the key of the
association is a member of the set. Typically a value such as
(), #t or #f is associated with the key.
Many operations can be viewed as computing a result that, depending on
whether the tree arguments are thought of as sets or maps, is known by
two different names. An example is wt-tree/member?, which, when
regarding the tree argument as a set, computes the set membership
operation, but, when regarding the tree as a discrete map,
wt-tree/member? is the predicate testing if the map is defined at
an element in its domain. Most names in this package have been chosen
based on interpreting the trees as sets, hence the name
wt-tree/member? rather than wt-tree/defined-at?.
The weight balanced tree implementation is a run-time-loadable option. To use weight balanced trees, execute
(load-option 'wt-tree)
once before calling any of the procedures defined here.
| 5.3.1 Construction of Weight-Balanced Trees | ||
| 5.3.2 Basic Operations on Weight-Balanced Trees | ||
| 5.3.3 Advanced Operations on Weight-Balanced Trees | ||
| 5.3.4 Indexing Operations on Weight-Balanced Trees |
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Binary trees require there to be a total order on the keys used to arrange the elements in the tree. Weight balanced trees are organized by types, where the type is an object encapsulating the ordering relation. Creating a tree is a two-stage process. First a tree type must be created from the predicate which gives the ordering. The tree type is then used for making trees, either empty or singleton trees or trees from other aggregate structures like association lists. Once created, a tree ‘knows’ its type and the type is used to test compatibility between trees in operations taking two trees. Usually a small number of tree types are created at the beginning of a program and used many times throughout the program’s execution.
This procedure creates and returns a new tree type based on the ordering
predicate key<?.
Key<? must be a total ordering, having the property that for all
key values a, b and c:
(key<? a a) ⇒ #f
(and (key<? a b) (key<? b a)) ⇒ #f
(if (and (key<? a b) (key<? b c))
(key<? a c)
#t) ⇒ #t
Two key values are assumed to be equal if neither is less than the other by key<?.
Each call to make-wt-tree-type returns a distinct value, and
trees are only compatible if their tree types are eq?. A
consequence is that trees that are intended to be used in binary tree
operations must all be created with a tree type originating from the
same call to make-wt-tree-type.
A standard tree type for trees with numeric keys. Number-wt-type
could have been defined by
(define number-wt-type (make-wt-tree-type <))
A standard tree type for trees with string keys. String-wt-type
could have been defined by
(define string-wt-type (make-wt-tree-type string<?))
This procedure creates and returns a newly allocated weight balanced
tree. The tree is empty, i.e. it contains no associations.
Wt-tree-type is a weight balanced tree type obtained by calling
make-wt-tree-type; the returned tree has this type.
This procedure creates and returns a newly allocated weight balanced
tree. The tree contains a single association, that of datum with
key. Wt-tree-type is a weight balanced tree type obtained
by calling make-wt-tree-type; the returned tree has this type.
Returns a newly allocated weight-balanced tree that contains the same associations as alist. This procedure is equivalent to:
(lambda (type alist)
(let ((tree (make-wt-tree type)))
(for-each (lambda (association)
(wt-tree/add! tree
(car association)
(cdr association)))
alist)
tree))
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This section describes the basic tree operations on weight balanced trees. These operations are the usual tree operations for insertion, deletion and lookup, some predicates and a procedure for determining the number of associations in a tree.
Returns #t if object is a weight-balanced tree, otherwise
returns #f.
Returns #t if wt-tree contains no associations, otherwise
returns #f.
Returns the number of associations in wt-tree, an exact non-negative integer. This operation takes constant time.
Returns a new tree containing all the associations in wt-tree and the association of datum with key. If wt-tree already had an association for key, the new association overrides the old. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.
Associates datum with key in wt-tree and returns an unspecified value. If wt-tree already has an association for key, that association is replaced. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.
Returns #t if wt-tree contains an association for
key, otherwise returns #f. The average and worst-case
times required by this operation are proportional to the logarithm of
the number of associations in wt-tree.
Returns the datum associated with key in wt-tree. If wt-tree doesn’t contain an association for key, default is returned. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.
Returns a new tree containing all the associations in wt-tree, except that if wt-tree contains an association for key, it is removed from the result. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.
If wt-tree contains an association for key the association is removed. Returns an unspecified value. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in wt-tree.
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In the following the size of a tree is the number of associations that the tree contains, and a smaller tree contains fewer associations.
Returns a new tree containing all and only the associations in wt-tree which have a key that is less than bound in the ordering relation of the tree type of wt-tree. The average and worst-case times required by this operation are proportional to the logarithm of the size of wt-tree.
Returns a new tree containing all and only the associations in wt-tree which have a key that is greater than bound in the ordering relation of the tree type of wt-tree. The average and worst-case times required by this operation are proportional to the logarithm of size of wt-tree.
Returns a new tree containing all the associations from both trees.
This operation is asymmetric: when both trees have an association for
the same key, the returned tree associates the datum from wt-tree-2
with the key. Thus if the trees are viewed as discrete maps then
wt-tree/union computes the map override of wt-tree-1 by
wt-tree-2. If the trees are viewed as sets the result is the set
union of the arguments.
The worst-case time required by this operation
is proportional to the sum of the sizes of both trees.
If the minimum key of one tree is greater than the maximum key of
the other tree then the time required is at worst proportional to
the logarithm of the size of the larger tree.
Returns a new tree containing all and only those associations from
wt-tree-1 which have keys appearing as the key of an association
in wt-tree-2. Thus the associated data in the result are those
from wt-tree-1. If the trees are being used as sets the result is
the set intersection of the arguments. As a discrete map operation,
wt-tree/intersection computes the domain restriction of
wt-tree-1 to (the domain of) wt-tree-2.
The time required by this operation is never worse that proportional to
the sum of the sizes of the trees.
Returns a new tree containing all and only those associations from wt-tree-1 which have keys that do not appear as the key of an association in wt-tree-2. If the trees are viewed as sets the result is the asymmetric set difference of the arguments. As a discrete map operation, it computes the domain restriction of wt-tree-1 to the complement of (the domain of) wt-tree-2. The time required by this operation is never worse that proportional to the sum of the sizes of the trees.
Returns #t iff the key of each association in wt-tree-1 is
the key of some association in wt-tree-2, otherwise returns #f.
Viewed as a set operation, wt-tree/subset? is the improper subset
predicate.
A proper subset predicate can be constructed:
(define (proper-subset? s1 s2)
(and (wt-tree/subset? s1 s2)
(< (wt-tree/size s1) (wt-tree/size s2))))
As a discrete map operation, wt-tree/subset? is the subset
test on the domain(s) of the map(s). In the worst-case the time
required by this operation is proportional to the size of
wt-tree-1.
Returns #t iff for every association in wt-tree-1 there is
an association in wt-tree-2 that has the same key, and vice
versa.
Viewing the arguments as sets wt-tree/set-equal? is the set
equality predicate. As a map operation it determines if two maps are
defined on the same domain.
This procedure is equivalent to
(lambda (wt-tree-1 wt-tree-2)
(and (wt-tree/subset? wt-tree-1 wt-tree-2
(wt-tree/subset? wt-tree-2 wt-tree-1)))
In the worst-case the time required by this operation is proportional to the size of the smaller tree.
This procedure reduces wt-tree by combining all the associations,
using an reverse in-order traversal, so the associations are visited in
reverse order. Combiner is a procedure of three arguments: a key,
a datum and the accumulated result so far. Provided combiner
takes time bounded by a constant, wt-tree/fold takes time
proportional to the size of wt-tree.
A sorted association list can be derived simply:
(wt-tree/fold (lambda (key datum list)
(cons (cons key datum) list))
'()
wt-tree))
The data in the associations can be summed like this:
(wt-tree/fold (lambda (key datum sum) (+ sum datum))
0
wt-tree)
This procedure traverses the tree in-order, applying action to
each association.
The associations are processed in increasing order of their keys.
Action is a procedure of two arguments which take the key and
datum respectively of the association.
Provided action takes time bounded by a constant,
wt-tree/for-each takes time proportional to in the size of
wt-tree.
The example prints the tree:
(wt-tree/for-each (lambda (key value)
(display (list key value)))
wt-tree))
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Weight balanced trees support operations that view the tree as sorted sequence of associations. Elements of the sequence can be accessed by position, and the position of an element in the sequence can be determined, both in logarthmic time.
Returns the 0-based indexth association of wt-tree in the
sorted sequence under the tree’s ordering relation on the keys.
wt-tree/index returns the indexth key,
wt-tree/index-datum returns the datum associated with the
indexth key and wt-tree/index-pair returns a new pair
(key . datum) which is the cons of the
indexth key and its datum. The average and worst-case times
required by this operation are proportional to the logarithm of the
number of associations in the tree.
These operations signal an error if the tree is empty, if
index<0, or if index is greater than or equal to the
number of associations in the tree.
Indexing can be used to find the median and maximum keys in the tree as follows:
median: (wt-tree/index wt-tree
(quotient (wt-tree/size wt-tree) 2))
maximum: (wt-tree/index wt-tree
(-1+ (wt-tree/size wt-tree)))
Determines the 0-based position of key in the sorted sequence of
the keys under the tree’s ordering relation, or #f if the tree
has no association with for key. This procedure returns either an
exact non-negative integer or #f. The average and worst-case
times required by this operation are proportional to the logarithm of
the number of associations in the tree.
Returns the association of wt-tree that has the least key under
the tree’s ordering relation. wt-tree/min returns the least key,
wt-tree/min-datum returns the datum associated with the least key
and wt-tree/min-pair returns a new pair (key . datum)
which is the cons of the minimum key and its datum. The average
and worst-case times required by this operation are proportional to the
logarithm of the number of associations in the tree.
These operations signal an error if the tree is empty. They could be written
(define (wt-tree/min tree) (wt-tree/index tree 0)) (define (wt-tree/min-datum tree) (wt-tree/index-datum tree 0)) (define (wt-tree/min-pair tree) (wt-tree/index-pair tree 0))
Returns a new tree containing all of the associations in wt-tree except the association with the least key under the wt-tree’s ordering relation. An error is signalled if the tree is empty. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree. This operation is equivalent to
(wt-tree/delete wt-tree (wt-tree/min wt-tree))
Removes the association with the least key under the wt-tree’s ordering relation. An error is signalled if the tree is empty. The average and worst-case times required by this operation are proportional to the logarithm of the number of associations in the tree. This operation is equivalent to
(wt-tree/delete! wt-tree (wt-tree/min wt-tree))
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| 6.1 Data Structures | Various data structures. | |
| 6.2 Procedures | Miscellaneous utility procedures. | |
| 6.3 Standards Support | Support for Scheme Standards. | |
| 6.4 Session Support | REPL and Debugging. | |
| 6.5 Extra-SLIB Packages |
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| 6.1.1 Arrays | ’array | |
| 6.1.2 Array Mapping | ’array-for-each | |
| 6.1.3 Association Lists | ’alist | |
| 6.1.4 Byte | ’byte | |
| 6.1.5 Collections | ’collect | |
| 6.1.6 Dynamic Data Type | ’dynamic | |
| 6.1.7 Hash Tables | ’hash-table | |
| 6.1.8 Hashing | ’hash, ’sierpinski, ’soundex | |
| 6.1.9 Macroless Object System | ’object | |
| 6.1.10 Priority Queues | ’priority-queue | |
| 6.1.11 Queues | ’queue | |
| 6.1.12 Records | ’record | |
| 6.1.13 Structures | ’struct, ’structure |
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Returns #t if the obj is an array, and #f if not.
Creates and returns an array that has as many dimensins as there are bounds and fills it with initial-value.
When constructing an array, bound is either an inclusive range of indices expressed as a two element list, or an upper bound expressed as a single integer. So
(make-array 'foo 3 3) ≡ (make-array 'foo '(0 2) '(0 2))
make-shared-array can be used to create shared subarrays of other
arrays. The mapper is a function that translates coordinates in
the new array into coordinates in the old array. A mapper must be
linear, and its range must stay within the bounds of the old array, but
it can be otherwise arbitrary. A simple example:
(define fred (make-array #f 8 8))
(define freds-diagonal
(make-shared-array fred (lambda (i) (list i i)) 8))
(array-set! freds-diagonal 'foo 3)
(array-ref fred 3 3)
⇒ FOO
(define freds-center
(make-shared-array fred (lambda (i j) (list (+ 3 i) (+ 3 j)))
2 2))
(array-ref freds-center 0 0)
⇒ FOO
Returns the number of dimensions of obj. If obj is not an array, 0 is returned.
array-shape returns a list of inclusive bounds. So:
(array-shape (make-array 'foo 3 5)) ⇒ ((0 2) (0 4))
array-dimensions is similar to array-shape but replaces
elements with a 0 minimum with one greater than the maximum. So:
(array-dimensions (make-array 'foo 3 5)) ⇒ (3 5)
Returns #t if its arguments would be acceptable to
array-ref.
Returns the element at the (index1, index2) element
in array.
The functions are just fast versions of array-ref and
array-set! that take a fixed number of arguments, and perform no
bounds checking.
If you comment out the bounds checking code, this is about as efficient as you could ask for without help from the compiler.
An exercise left to the reader: implement the rest of APL.
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array1, … must have the same number of dimensions as array0 and have a range for each index which includes the range for the corresponding index in array0. proc is applied to each tuple of elements of array1 … and the result is stored as the corresponding element in array0. The value returned is unspecified. The order of application is unspecified.
proc is applied to each tuple of elements of array0 … in row-major order. The value returned is unspecified.
Returns an array of lists of indexes for array such that, if li is a list of indexes for which array is defined, (equal? li (apply array-ref (array-indexes array) li)).
applies proc to the indices of each element of array in turn, storing the result in the corresponding element. The value returned and the order of application are unspecified.
One can implement array-indexes as
(define (array-indexes array)
(let ((ra (apply make-array #f (array-shape array))))
(array-index-map! ra (lambda x x))
ra))
Another example:
(define (apl:index-generator n)
(let ((v (make-uniform-vector n 1)))
(array-index-map! v (lambda (i) i))
v))
Copies every element from vector or array source to the corresponding element of destination. destination must have the same rank as source, and be at least as large in each dimension. The order of copying is unspecified.
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Alist functions provide utilities for treating a list of key-value pairs as an associative database. These functions take an equality predicate, pred, as an argument. This predicate should be repeatable, symmetric, and transitive.
Alist functions can be used with a secondary index method such as hash tables for improved performance.
Returns an association function (like assq, assv, or
assoc) corresponding to pred. The returned function
returns a key-value pair whose key is pred-equal to its first
argument or #f if no key in the alist is pred-equal to the
first argument.
Returns a procedure of 2 arguments, alist and key, which
returns the value associated with key in alist or #f if
key does not appear in alist.
Returns a procedure of 3 arguments, alist, key, and value, which returns an alist with key and value associated. Any previous value associated with key will be lost. This returned procedure may or may not have side effects on its alist argument. An example of correct usage is:
(define put (alist-associator string-ci=?)) (define alist '()) (set! alist (put alist "Foo" 9))
Returns a procedure of 2 arguments, alist and key, which returns an alist with an association whose key is key removed. This returned procedure may or may not have side effects on its alist argument. An example of correct usage is:
(define rem (alist-remover string-ci=?)) (set! alist (rem alist "foo"))
Returns a new association list formed by mapping proc over the keys and values of alist. proc must be a function of 2 arguments which returns the new value part.
Applies proc to each pair of keys and values of alist. proc must be a function of 2 arguments. The returned value is unspecified.
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(require 'byte)
Some algorithms are expressed in terms of arrays of small integers. Using Scheme strings to implement these arrays is not portable vis-a-vis the correspondence between integers and characters and non-ascii character sets. These functions abstract the notion of a byte.
k must be a valid index of bytes. byte-ref returns
byte k of bytes using zero-origin indexing.
k must be a valid index of bytes%, and byte must be a
small integer. Byte-set! stores byte in element k
of bytes
and returns an unspecified value.
Make-bytes returns a newly allocated byte-array of
length k. If byte is given, then all elements of the
byte-array are initialized to byte, otherwise the contents of the
byte-array are unspecified.
Writes the byte byte (not an external representation of the
byte) to the given port and returns an unspecified value. The
port argument may be omitted, in which case it defaults to the value
returned by current-output-port.
Returns the next byte available from the input port, updating
the port to point to the following byte. If no more bytes
are available, an end of file object is returned. Port may be
omitted, in which case it defaults to the value returned by
current-input-port.
Returns a newly allocated byte-array composed of the arguments.
Bytes->list returns a newly allocated list of the
bytes that make up the given byte-array. List->bytes
returns a newly allocated byte-array formed from the small integers in
the list bytes. Bytes->list and list->bytes are
inverses so far as equal? is concerned.
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Routines for managing collections. Collections are aggregate data structures supporting iteration over their elements, similar to the Dylan(TM) language, but with a different interface. They have elements indexed by corresponding keys, although the keys may be implicit (as with lists).
New types of collections may be defined as YASOS objects (See section Yasos). They must support the following operations:
(collection? self) (always returns #t);
(size self) returns the number of elements in the collection;
(print self port) is a specialized print operation
for the collection which prints a suitable representation on the given
port or returns it as a string if port is #t;
(gen-elts self) returns a thunk which on successive
invocations yields elements of self in order or gives an error if
it is invoked more than (size self) times;
(gen-keys self) is like gen-elts, but yields the
collection’s keys in order.
They might support specialized for-each-key and
for-each-elt operations.
A predicate, true initially of lists, vectors and strings. New sorts of
collections must answer #t to collection?.
proc is a procedure taking as many arguments as there are
collections (at least one). The collections are iterated
over in their natural order and proc is applied to the elements
yielded by each iteration in turn. The order in which the arguments are
supplied corresponds to te order in which the collections appear.
do-elts is used when only side-effects of proc are of
interest and its return value is unspecified. map-elts returns a
collection (actually a vector) of the results of the applications of
proc.
Example:
(map-elts + (list 1 2 3) (vector 1 2 3)) ⇒ #(2 4 6)
These are analogous to map-elts and do-elts, but each
iteration is over the collections’ keys rather than their
elements.
Example:
(map-keys + (list 1 2 3) (vector 1 2 3)) ⇒ #(0 2 4)
These are like do-keys and do-elts but only for a single
collection; they are potentially more efficient.
A generalization of the list-based comlist:reduce-init
(See section Lists as sequences) to collections which will shadow the
list-based version if (require 'collect) follows
(require 'common-list-functions) (See section Common List Functions).
Examples:
(reduce + 0 (vector 1 2 3)) ⇒ 6 (reduce union '() '((a b c) (b c d) (d a))) ⇒ (c b d a).
A generalization of the list-based some (See section Lists as sequences) to collections.
Example:
(any? odd? (list 2 3 4 5)) ⇒ #t
A generalization of the list-based every (See section Lists as sequences) to collections.
Example:
(every? collection? '((1 2) #(1 2))) ⇒ #t
Returns #t iff there are no elements in collection.
(empty? collection) ≡ (zero? (size collection))
Returns the number of elements in collection.
See See section Setters for a definition of setter. N.B.
(setter list-ref) doesn’t work properly for element 0 of a
list.
Here is a sample collection: simple-table which is also a
table.
(define-predicate TABLE?)
(define-operation (LOOKUP table key failure-object))
(define-operation (ASSOCIATE! table key value)) ;; returns key
(define-operation (REMOVE! table key)) ;; returns value
(define (MAKE-SIMPLE-TABLE)
(let ( (table (list)) )
(object
;; table behaviors
((TABLE? self) #t)
((SIZE self) (size table))
((PRINT self port) (format port "#<SIMPLE-TABLE>"))
((LOOKUP self key failure-object)
(cond
((assq key table) => cdr)
(else failure-object)
))
((ASSOCIATE! self key value)
(cond
((assq key table)
=> (lambda (bucket) (set-cdr! bucket value) key))
(else
(set! table (cons (cons key value) table))
key)
))
((REMOVE! self key);; returns old value
(cond
((null? table) (slib:error "TABLE:REMOVE! Key not found: " key))
((eq? key (caar table))
(let ( (value (cdar table)) )
(set! table (cdr table))
value)
)
(else
(let loop ( (last table) (this (cdr table)) )
(cond
((null? this)
(slib:error "TABLE:REMOVE! Key not found: " key))
((eq? key (caar this))
(let ( (value (cdar this)) )
(set-cdr! last (cdr this))
value)
)
(else
(loop (cdr last) (cdr this)))
) ) )
))
;; collection behaviors
((COLLECTION? self) #t)
((GEN-KEYS self) (collect:list-gen-elts (map car table)))
((GEN-ELTS self) (collect:list-gen-elts (map cdr table)))
((FOR-EACH-KEY self proc)
(for-each (lambda (bucket) (proc (car bucket))) table)
)
((FOR-EACH-ELT self proc)
(for-each (lambda (bucket) (proc (cdr bucket))) table)
)
) ) )
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Create and returns a new dynamic whose global value is obj.
Returns true if and only if obj is a dynamic. No object
satisfying dynamic? satisfies any of the other standard type
predicates.
Return the value of the given dynamic in the current dynamic environment.
Change the value of the given dynamic to obj in the current dynamic environment. The returned value is unspecified.
Invoke and return the value of the given thunk in a new, nested dynamic environment in which the given dynamic has been bound to a new location whose initial contents are the value obj. This dynamic environment has precisely the same extent as the invocation of the thunk and is thus captured by continuations created within that invocation and re-established by those continuations when they are invoked.
The dynamic-bind macro is not implemented.
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Returns a hash function (like hashq, hashv, or
hash) corresponding to the equality predicate pred.
pred should be eq?, eqv?, equal?, =,
char=?, char-ci=?, string=?, or
string-ci=?.
A hash table is a vector of association lists.
Returns a vector of k empty (association) lists.
Hash table functions provide utilities for an associative database.
These functions take an equality predicate, pred, as an argument.
pred should be eq?, eqv?, equal?, =,
char=?, char-ci=?, string=?, or
string-ci=?.
Returns a hash association function of 2 arguments, key and
hashtab, corresponding to pred. The returned function
returns a key-value pair whose key is pred-equal to its first
argument or #f if no key in hashtab is pred-equal to
the first argument.
Returns a procedure of 3 arguments, hashtab and key, which
returns the value associated with key in hashtab or
#f if key does not appear in hashtab.
Returns a procedure of 3 arguments, hashtab, key, and value, which modifies hashtab so that key and value associated. Any previous value associated with key will be lost.
Returns a procedure of 2 arguments, hashtab and key, which modifies hashtab so that the association whose key is key is removed.
Returns a new hash table formed by mapping proc over the keys and values of hash-table. proc must be a function of 2 arguments which returns the new value part.
Applies proc to each pair of keys and values of hash-table. proc must be a function of 2 arguments. The returned value is unspecified.
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These hashing functions are for use in quickly classifying objects. Hash tables use these functions.
Returns an exact non-negative integer less than k. For each non-negative integer less than k there are arguments obj for which the hashing functions applied to obj and k returns that integer.
For hashq, (eq? obj1 obj2) implies (= (hashq obj1 k)
(hashq obj2)).
For hashv, (eqv? obj1 obj2) implies (= (hashv obj1 k)
(hashv obj2)).
For hash, (equal? obj1 obj2) implies (= (hash obj1 k)
(hash obj2)).
hash, hashv, and hashq return in time bounded by a
constant. Notice that items having the same hash implies the
items have the same hashv implies the items have the same
hashq.
Returns a procedure (eg hash-function) of 2 numeric arguments which preserves nearness in its mapping from NxN to N.
max-coordinate is the maximum coordinate (a positive integer) of a population of points. The returned procedures is a function that takes the x and y coordinates of a point, (non-negative integers) and returns an integer corresponding to the relative position of that point along a Sierpinski curve. (You can think of this as computing a (pseudo-) inverse of the Sierpinski spacefilling curve.)
Example use: Make an indexer (hash-function) for integer points lying in square of integer grid points [0,99]x[0,99]:
(define space-key (make-sierpinski-indexer 100))
Now let’s compute the index of some points:
(space-key 24 78) ⇒ 9206 (space-key 23 80) ⇒ 9172
Note that locations (24, 78) and (23, 80) are near in index and therefore, because the Sierpinski spacefilling curve is continuous, we know they must also be near in the plane. Nearness in the plane does not, however, necessarily correspond to nearness in index, although it tends to be so.
Example applications:
Computes the soundex hash of name. Returns a string of an initial letter and up to three digits between 0 and 6. Soundex supposedly has the property that names that sound similar in normal English pronunciation tend to map to the same key.
Soundex was a classic algorithm used for manual filing of personal records before the advent of computers. It performs adequately for English names but has trouble with other nationalities.
See Knuth, Vol. 3 Sorting and searching, pp 391–2
To manage unusual inputs, soundex omits all non-alphabetic
characters. Consequently, in this implementation:
(soundex <string of blanks>) ⇒ "" (soundex "") ⇒ ""
Examples from Knuth:
(map soundex '("Euler" "Gauss" "Hilbert" "Knuth"
"Lloyd" "Lukasiewicz"))
⇒ ("E460" "G200" "H416" "K530" "L300" "L222")
(map soundex '("Ellery" "Ghosh" "Heilbronn" "Kant"
"Ladd" "Lissajous"))
⇒ ("E460" "G200" "H416" "K530" "L300" "L222")
Some cases in which the algorithm fails (Knuth):
(map soundex '("Rogers" "Rodgers")) ⇒ ("R262" "R326")
(map soundex '("Sinclair" "St. Clair")) ⇒ ("S524" "S324")
(map soundex '("Tchebysheff" "Chebyshev")) ⇒ ("T212" "C121")
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Returns a binary heap suitable which can be used for priority queue operations.
Returns the number of elements in heap.
Inserts item into heap. item can be inserted multiple times. The value returned is unspecified.
Returns the item which is larger than all others according to the
pred<? argument to make-heap. If there are no items in
heap, an error is signaled.
The algorithm for priority queues was taken from Introduction to Algorithms by T. Cormen, C. Leiserson, R. Rivest. 1989 MIT Press.
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A queue is a list where elements can be added to both the front and rear, and removed from the front (i.e., they are what are often called dequeues). A queue may also be used like a stack.
Returns a new, empty queue.
Returns #t if obj is a queue.
Returns #t if the queue q is empty.
Adds datum to the front of queue q.
Adds datum to the rear of queue q.
All of the following functions raise an error if the queue q is empty.
Returns the datum at the front of the queue q.
Returns the datum at the rear of the queue q.
Both of these procedures remove and return the datum at the front of the
queue. queue-pop! is used to suggest that the queue is being
used like a stack.
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The Record package provides a facility for user to define their own record data types.
Returns a record-type descriptor, a value representing a new data type disjoint from all others. The type-name argument must be a string, but is only used for debugging purposes (such as the printed representation of a record of the new type). The field-names argument is a list of symbols naming the fields of a record of the new type. It is an error if the list contains any duplicates. It is unspecified how record-type descriptors are represented.
Returns a procedure for constructing new members of the type represented
by rtd. The returned procedure accepts exactly as many arguments
as there are symbols in the given list, field-names; these are
used, in order, as the initial values of those fields in a new record,
which is returned by the constructor procedure. The values of any
fields not named in that list are unspecified. The field-names
argument defaults to the list of field names in the call to
make-record-type that created the type represented by rtd;
if the field-names argument is provided, it is an error if it
contains any duplicates or any symbols not in the default list.
Returns a procedure for testing membership in the type represented by rtd. The returned procedure accepts exactly one argument and returns a true value if the argument is a member of the indicated record type; it returns a false value otherwise.
Returns a procedure for reading the value of a particular field of a
member of the type represented by rtd. The returned procedure
accepts exactly one argument which must be a record of the appropriate
type; it returns the current value of the field named by the symbol
field-name in that record. The symbol field-name must be a
member of the list of field-names in the call to make-record-type
that created the type represented by rtd.
Returns a procedure for writing the value of a particular field of a
member of the type represented by rtd. The returned procedure
accepts exactly two arguments: first, a record of the appropriate type,
and second, an arbitrary Scheme value; it modifies the field named by
the symbol field-name in that record to contain the given value.
The returned value of the modifier procedure is unspecified. The symbol
field-name must be a member of the list of field-names in the call
to make-record-type that created the type represented by
rtd.
In May of 1996, as a product of discussion on the rrrs-authors
mailing list, I rewrote ‘record.scm’ to portably implement type
disjointness for record data types.
As long as an implementation’s procedures are opaque and the
record code is loaded before other programs, this will give
disjoint record types which are unforgeable and incorruptible by R4RS
procedures.
As a consequence, the procedures record?,
record-type-descriptor, record-type-name.and
record-type-field-names are no longer supported.
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(require 'struct) (uses defmacros)
defmacros which implement records from the book
Essentials of Programming Languages by Daniel P. Friedman, M.
Wand and C.T. Haynes. Copyright 1992 Jeff Alexander, Shinnder Lee, and
Lewis Patterson
Matthew McDonald <mafm@cs.uwa.edu.au> added field setters.
Defines several functions pertaining to record-name tag:
…
…
Here is an example of its use.
(define-record term (operator left right)) ⇒ #<unspecified> (define foo (make-term 'plus 1 2)) ⇒ foo (term->left foo) ⇒ 1 (set-term-left! foo 2345) ⇒ #<unspecified> (term->left foo) ⇒ 2345
executes the following for the matching clause:
((lambda (var1 var …) body) (tag->var1 exp) (tag->var2 exp) …)
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Anything that doesn’t fall neatly into any of the other categories winds up here.
| 6.2.1 Common List Functions | ’common-list-functions | |
| 6.2.2 Tree operations | ’tree | |
| 6.2.3 Chapter Ordering | ’chapter-order | |
| 6.2.4 Sorting | ’sort | |
| 6.2.5 Topological Sort | Keep your socks on. | |
| 6.2.6 String-Case | ’string-case | |
| 6.2.7 String Ports | ’string-port | |
| 6.2.8 String Search | Also Search from a Port. | |
| 6.2.9 Line I/O | ’line-i/o | |
| 6.2.10 Multi-Processing | ’process |
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(require 'common-list-functions)
The procedures below follow the Common LISP equivalents apart from optional arguments in some cases.
| 6.2.1.1 List construction | ||
| 6.2.1.2 Lists as sets | ||
| 6.2.1.3 Lists as sequences | ||
| 6.2.1.4 Destructive list operations | ||
| 6.2.1.5 Non-List functions |
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make-list creates and returns a list of k elements. If
init is included, all elements in the list are initialized to
init.
Example:
(make-list 3) ⇒ (#<unspecified> #<unspecified> #<unspecified>) (make-list 5 'foo) ⇒ (foo foo foo foo foo)
Works like list except that the cdr of the last pair is the last
argument unless there is only one argument, when the result is just that
argument. Sometimes called cons*. E.g.:
(list* 1) ⇒ 1 (list* 1 2 3) ⇒ (1 2 . 3) (list* 1 2 '(3 4)) ⇒ (1 2 3 4) (list* args '()) ≡ (list args)
copy-list makes a copy of lst using new pairs and returns
it. Only the top level of the list is copied, i.e., pairs forming
elements of the copied list remain eq? to the corresponding
elements of the original; the copy is, however, not eq? to the
original, but is equal? to it.
Example:
(copy-list '(foo foo foo)) ⇒ (foo foo foo) (define q '(foo bar baz bang)) (define p q) (eq? p q) ⇒ #t (define r (copy-list q)) (eq? q r) ⇒ #f (equal? q r) ⇒ #t (define bar '(bar)) (eq? bar (car (copy-list (list bar 'foo)))) ⇒ #t
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eqv? is used to test for membership by procedures which treat
lists as sets.
adjoin returns the adjoint of the element e and the list
l. That is, if e is in l, adjoin returns
l, otherwise, it returns (cons e l).
Example:
(adjoin 'baz '(bar baz bang)) ⇒ (bar baz bang) (adjoin 'foo '(bar baz bang)) ⇒ (foo bar baz bang)
union returns the combination of l1 and l2.
Duplicates between l1 and l2 are culled. Duplicates within
l1 or within l2 may or may not be removed.
Example:
(union '(1 2 3 4) '(5 6 7 8)) ⇒ (4 3 2 1 5 6 7 8) (union '(1 2 3 4) '(3 4 5 6)) ⇒ (2 1 3 4 5 6)
intersection returns all elements that are in both l1 and
l2.
Example:
(intersection '(1 2 3 4) '(3 4 5 6)) ⇒ (3 4) (intersection '(1 2 3 4) '(5 6 7 8)) ⇒ ()
set-difference returns the union of all elements that are in
l1 but not in l2.
Example:
(set-difference '(1 2 3 4) '(3 4 5 6)) ⇒ (1 2) (set-difference '(1 2 3 4) '(1 2 3 4 5 6)) ⇒ ()
member-if returns lst if (pred element)
is #t for any element in lst. Returns #f if
pred does not apply to any element in lst.
Example:
(member-if vector? '(1 2 3 4)) ⇒ #f (member-if number? '(1 2 3 4)) ⇒ (1 2 3 4)
pred is a boolean function of as many arguments as there are list
arguments to some i.e., lst plus any optional arguments.
pred is applied to successive elements of the list arguments in
order. some returns #t as soon as one of these
applications returns #t, and is #f if none returns
#t. All the lists should have the same length.
Example:
(some odd? '(1 2 3 4)) ⇒ #t (some odd? '(2 4 6 8)) ⇒ #f (some > '(2 3) '(1 4)) ⇒ #f
every is analogous to some except it returns #t if
every application of pred is #t and #f
otherwise.
Example:
(every even? '(1 2 3 4)) ⇒ #f (every even? '(2 4 6 8)) ⇒ #t (every > '(2 3) '(1 4)) ⇒ #f
notany is analogous to some but returns #t if no
application of pred returns #t or #f as soon as any
one does.
notevery is analogous to some but returns #t as soon
as an application of pred returns #f, and #f
otherwise.
Example:
(notevery even? '(1 2 3 4)) ⇒ #t (notevery even? '(2 4 6 8)) ⇒ #f
find-if searches for the first element in lst such
that (pred element) returns #t. If it finds
any such element in lst, element is returned.
Otherwise, #f is returned.
Example:
(find-if number? '(foo 1 bar 2)) ⇒ 1 (find-if number? '(foo bar baz bang)) ⇒ #f (find-if symbol? '(1 2 foo bar)) ⇒ foo
remove removes all occurrences of elt from lst using
eqv? to test for equality and returns everything that’s left.
N.B.: other implementations (Chez, Scheme->C and T, at least) use
equal? as the equality test.
Example:
(remove 1 '(1 2 1 3 1 4 1 5)) ⇒ (2 3 4 5) (remove 'foo '(bar baz bang)) ⇒ (bar baz bang)
remove-if removes all elements from lst where
(pred element) is #t and returns everything
that’s left.
Example:
(remove-if number? '(1 2 3 4)) ⇒ () (remove-if even? '(1 2 3 4 5 6 7 8)) ⇒ (1 3 5 7)
remove-if-not removes all elements from lst for which
(pred element) is #f and returns everything that’s
left.
Example:
(remove-if-not number? '(foo bar baz)) ⇒ () (remove-if-not odd? '(1 2 3 4 5 6 7 8)) ⇒ (1 3 5 7)
returns #t if 2 members of lst are equal?, #f
otherwise.
Example:
(has-duplicates? '(1 2 3 4)) ⇒ #f (has-duplicates? '(2 4 3 4)) ⇒ #t
The procedure remove-duplicates uses member (rather than
memv).
returns a copy of lst with its duplicate members removed.
Elements are considered duplicate if they are equal?.
Example:
(remove-duplicates '(1 2 3 4)) ⇒ (4 3 2 1) (remove-duplicates '(2 4 3 4)) ⇒ (3 4 2)
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position returns the 0-based position of obj in lst,
or #f if obj does not occur in lst.
Example:
(position 'foo '(foo bar baz bang)) ⇒ 0 (position 'baz '(foo bar baz bang)) ⇒ 2 (position 'oops '(foo bar baz bang)) ⇒ #f
reduce combines all the elements of a sequence using a binary
operation (the combination is left-associative). For example, using
+, one can add up all the elements. reduce allows you to
apply a function which accepts only two arguments to more than 2
objects. Functional programmers usually refer to this as foldl.
collect:reduce (See section Collections) provides a version of
collect generalized to collections.
Example:
(reduce + '(1 2 3 4))
⇒ 10
(define (bad-sum . l) (reduce + l))
(bad-sum 1 2 3 4)
≡ (reduce + (1 2 3 4))
≡ (+ (+ (+ 1 2) 3) 4)
⇒ 10
(bad-sum)
≡ (reduce + ())
⇒ ()
(reduce string-append '("hello" "cruel" "world"))
≡ (string-append (string-append "hello" "cruel") "world")
⇒ "hellocruelworld"
(reduce anything '())
⇒ ()
(reduce anything '(x))
⇒ x
What follows is a rather non-standard implementation of reverse
in terms of reduce and a combinator elsewhere called
C.
;;; Contributed by Jussi Piitulainen (jpiitula@ling.helsinki.fi)
(define commute
(lambda (f)
(lambda (x y)
(f y x))))
(define reverse
(lambda (args)
(reduce-init (commute cons) '() args)))
reduce-init is the same as reduce, except that it implicitly
inserts init at the start of the list. reduce-init is
preferred if you want to handle the null list, the one-element, and
lists with two or more elements consistently. It is common to use the
operator’s idempotent as the initializer. Functional programmers
usually call this foldl.
Example:
(define (sum . l) (reduce-init + 0 l))
(sum 1 2 3 4)
≡ (reduce-init + 0 (1 2 3 4))
≡ (+ (+ (+ (+ 0 1) 2) 3) 4)
⇒ 10
(sum)
≡ (reduce-init + 0 '())
⇒ 0
(reduce-init string-append "@" '("hello" "cruel" "world"))
≡
(string-append (string-append (string-append "@" "hello")
"cruel")
"world")
⇒ "@hellocruelworld"
Given a differentiation of 2 arguments, diff, the following will
differentiate by any number of variables.
(define (diff* exp . vars) (reduce-init diff exp vars))
Example:
;;; Real-world example: Insertion sort using reduce-init.
(define (insert l item)
(if (null? l)
(list item)
(if (< (car l) item)
(cons (car l) (insert (cdr l) item))
(cons item l))))
(define (insertion-sort l) (reduce-init insert '() l))
(insertion-sort '(3 1 4 1 5)
≡ (reduce-init insert () (3 1 4 1 5))
≡ (insert (insert (insert (insert (insert () 3) 1) 4) 1) 5)
≡ (insert (insert (insert (insert (3)) 1) 4) 1) 5)
≡ (insert (insert (insert (1 3) 4) 1) 5)
≡ (insert (insert (1 3 4) 1) 5)
≡ (insert (1 1 3 4) 5)
⇒ (1 1 3 4 5)
last returns the last n elements of lst. n
must be a non-negative integer.
Example:
(last '(foo bar baz bang) 2) ⇒ (baz bang) (last '(1 2 3) 0) ⇒ 0
butlast returns all but the last n elements of
lst.
Example:
(butlast '(a b c d) 3) ⇒ (a) (butlast '(a b c d) 4) ⇒ ()
last and butlast split a list into two parts when given
identical arugments.
(last '(a b c d e) 2) ⇒ (d e) (butlast '(a b c d e) 2) ⇒ (a b c)
nthcdr takes n cdrs of lst and returns the
result. Thus (nthcdr 3 lst) ≡ (cdddr
lst)
Example:
(nthcdr 2 '(a b c d)) ⇒ (c d) (nthcdr 0 '(a b c d)) ⇒ (a b c d)
butnthcdr returns all but the nthcdr n elements of
lst.
Example:
(butnthcdr 3 '(a b c d)) ⇒ (a b c) (butnthcdr 4 '(a b c d)) ⇒ ()
nthcdr and butnthcdr split a list into two parts when
given identical arugments.
(nthcdr 2 '(a b c d e)) ⇒ (c d e) (butnthcdr 2 '(a b c d e)) ⇒ (a b)
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These procedures may mutate the list they operate on, but any such mutation is undefined.
nconc destructively concatenates its arguments. (Compare this
with append, which copies arguments rather than destroying them.)
Sometimes called append! (See section Rev2 Procedures).
Example: You want to find the subsets of a set. Here’s the obvious way:
(define (subsets set)
(if (null? set)
'(())
(append (mapcar (lambda (sub) (cons (car set) sub))
(subsets (cdr set)))
(subsets (cdr set)))))
But that does way more consing than you need. Instead, you could
replace the append with nconc, since you don’t have any
need for all the intermediate results.
Example:
(define x '(a b c)) (define y '(d e f)) (nconc x y) ⇒ (a b c d e f) x ⇒ (a b c d e f)
nconc is the same as append! in ‘sc2.scm’.
nreverse reverses the order of elements in lst by mutating
cdrs of the list. Sometimes called reverse!.
Example:
(define foo '(a b c)) (nreverse foo) ⇒ (c b a) foo ⇒ (a)
Some people have been confused about how to use nreverse,
thinking that it doesn’t return a value. It needs to be pointed out
that
(set! lst (nreverse lst))
is the proper usage, not
(nreverse lst)
The example should suffice to show why this is the case.
Destructive versions of remove remove-if, and
remove-if-not.
Example:
(define lst '(foo bar baz bang)) (delete 'foo lst) ⇒ (bar baz bang) lst ⇒ (foo bar baz bang) (define lst '(1 2 3 4 5 6 7 8 9)) (delete-if odd? lst) ⇒ (2 4 6 8) lst ⇒ (1 2 4 6 8)
Some people have been confused about how to use delete,
delete-if, and delete-if, thinking that they dont’ return
a value. It needs to be pointed out that
(set! lst (delete el lst))
is the proper usage, not
(delete el lst)
The examples should suffice to show why this is the case.
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and? checks to see if all its arguments are true. If they are,
and? returns #t, otherwise, #f. (In contrast to
and, this is a function, so all arguments are always evaluated
and in an unspecified order.)
Example:
(and? 1 2 3) ⇒ #t (and #f 1 2) ⇒ #f
or? checks to see if any of its arguments are true. If any is
true, or? returns #t, and #f otherwise. (To
or as and? is to and.)
Example:
(or? 1 2 #f) ⇒ #t (or? #f #f #f) ⇒ #f
Returns #t if object is not a pair and #f if it is
pair. (Called atom in Common LISP.)
(atom? 1) ⇒ #t (atom? '(1 2)) ⇒ #f (atom? #(1 2)) ; dubious! ⇒ #t
Returns a symbol name for the type of object.
Converts and returns object of type char, number,
string, symbol, list, or vector to
result-type (which must be one of these symbols).
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These are operations that treat lists a representations of trees.
subst makes a copy of tree, substituting new for
every subtree or leaf of tree which is equal? to old
and returns a modified tree. The original tree is unchanged, but
may share parts with the result.
substq and substv are similar, but test against old
using eq? and eqv? respectively.
Examples:
(substq 'tempest 'hurricane '(shakespeare wrote (the hurricane)))
⇒ (shakespeare wrote (the tempest))
(substq 'foo '() '(shakespeare wrote (twelfth night)))
⇒ (shakespeare wrote (twelfth night . foo) . foo)
(subst '(a . cons) '(old . pair)
'((old . spice) ((old . shoes) old . pair) (old . pair)))
⇒ ((old . spice) ((old . shoes) a . cons) (a . cons))
Makes a copy of the nested list structure tree using new pairs and
returns it. All levels are copied, so that none of the pairs in the
tree are eq? to the original ones – only the leaves are.
Example:
(define bar '(bar)) (copy-tree (list bar 'foo)) ⇒ ((bar) foo) (eq? bar (car (copy-tree (list bar 'foo)))) ⇒ #f
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The ‘chap:’ functions deal with strings which are ordered like chapter numbers (or letters) in a book. Each section of the string consists of consecutive numeric or consecutive aphabetic characters of like case.
Returns #t if the first non-matching run of alphabetic upper-case or the
first non-matching run of alphabetic lower-case or the first
non-matching run of numeric characters of string1 is
string<? than the corresponding non-matching run of characters of
string2.
(chap:string<? "a.9" "a.10") ⇒ #t
(chap:string<? "4c" "4aa") ⇒ #t
(chap:string<? "Revised^{3.99}" "Revised^{4}") ⇒ #t
Implement the corresponding chapter-order predicates.
Returns the next string in the chapter order. If string
has no alphabetic or numeric characters,
(string-append string "0") is returnd. The argument to
chap:next-string will always be chap:string<? than the result.
(chap:next-string "a.9") ⇒ "a.10"
(chap:next-string "4c") ⇒ "4d"
(chap:next-string "4z") ⇒ "4aa"
(chap:next-string "Revised^{4}") ⇒ "Revised^{5}"
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Many Scheme systems provide some kind of sorting functions. They do not, however, always provide the same sorting functions, and those that I have had the opportunity to test provided inefficient ones (a common blunder is to use quicksort which does not perform well).
Because sort and sort! are not in the standard, there is
very little agreement about what these functions look like. For
example, Dybvig says that Chez Scheme provides
(merge predicate list1 list2) (merge! predicate list1 list2) (sort predicate list) (sort! predicate list)
while MIT Scheme 7.1, following Common LISP, offers unstable
(sort list predicate)
TI PC Scheme offers
(sort! list/vector predicate?)
and Elk offers
(sort list/vector predicate?) (sort! list/vector predicate?)
Here is a comprehensive catalogue of the variations I have found.
sort and sort! may be provided.
sort may be provided without sort!.
sort! may be provided without sort.
<.
<=.
(sort predicate? sequence).
(sort sequence predicate?).
(sort sequence &optional (predicate? <)).
All of this variation really does not help anybody. A nice simple merge sort is both stable and fast (quite a lot faster than quick sort).
I am providing this source code with no restrictions at all on its use (but please retain D.H.D.Warren’s credit for the original idea). You may have to rename some of these functions in order to use them in a system which already provides incompatible or inferior sorts. For each of the functions, only the top-level define needs to be edited to do that.
I could have given these functions names which would not clash with any Scheme that I know of, but I would like to encourage implementors to converge on a single interface, and this may serve as a hint. The argument order for all functions has been chosen to be as close to Common LISP as made sense, in order to avoid NIH-itis.
Each of the five functions has a required last parameter which is
a comparison function. A comparison function f is a function of
2 arguments which acts like <. For example,
(not (f x x)) (and (f x y) (f y z)) ≡ (f x z)
The standard functions <, >, char<?, char>?,
char-ci<?, char-ci>?, string<?, string>?,
string-ci<?, and string-ci>? are suitable for use as
comparison functions. Think of (less? x y) as saying when
x must not precede y.
Returns #t when the sequence argument is in non-decreasing order
according to less? (that is, there is no adjacent pair … x
y … for which (less? y x)).
Returns #f when the sequence contains at least one out-of-order
pair. It is an error if the sequence is neither a list nor a vector.
This merges two lists, producing a completely new list as result. I
gave serious consideration to producing a Common-LISP-compatible
version. However, Common LISP’s sort is our sort! (well,
in fact Common LISP’s stable-sort is our sort!, merge sort
is fast as well as stable!) so adapting CL code to Scheme takes a
bit of work anyway. I did, however, appeal to CL to determine the
order of the arguments.
Merges two lists, re-using the pairs of list1 and list2 to build the result. If the code is compiled, and less? constructs no new pairs, no pairs at all will be allocated. The first pair of the result will be either the first pair of list1 or the first pair of list2, but you can’t predict which.
The code of merge and merge! could have been quite a bit
simpler, but they have been coded to reduce the amount of work done per
iteration. (For example, we only have one null? test per
iteration.)
Accepts either a list or a vector, and returns a new sequence which is
sorted. The new sequence is the same type as the input. Always
(sorted? (sort sequence less?) less?). The original sequence is
not altered in any way. The new sequence shares its elements
with the old one; no elements are copied.
Returns its sorted result in the original boxes. If the original sequence is a list, no new storage is allocated at all. If the original sequence is a vector, the sorted elements are put back in the same vector.
Some people have been confused about how to use sort!, thinking
that it doesn’t return a value. It needs to be pointed out that
(set! slist (sort! slist <))
is the proper usage, not
(sort! slist <)
Note that these functions do not accept a CL-style ‘:key’ argument. A simple device for obtaining the same expressiveness is to define
(define (keyed less? key) (lambda (x y) (less? (key x) (key y))))
and then, when you would have written
(sort a-sequence #'my-less :key #'my-key)
in Common LISP, just write
(sort! a-sequence (keyed my-less? my-key))
in Scheme.
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(require 'topological-sort) or (require 'tsort)
The algorithm is inspired by Cormen, Leiserson and Rivest (1990) Introduction to Algorithms, chapter 23.
where
is a list of sublists. The car of each sublist is a vertex. The cdr is the adjacency list of that vertex, i.e. a list of all vertices to which there exists an edge from the car vertex.
is one of eq?, eqv?, equal?, =,
char=?, char-ci=?, string=?, or string-ci=?.
Sort the directed acyclic graph dag so that for every edge from vertex u to v, u will come before v in the resulting list of vertices.
Time complexity: O (|V| + |E|)
Example (from Cormen):
Prof. Bumstead topologically sorts his clothing when getting dressed. The first argument to ‘tsort’ describes which garments he needs to put on before others. (For example, Prof Bumstead needs to put on his shirt before he puts on his tie or his belt.) ‘tsort’ gives the correct order of dressing:
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The obvious string conversion routines. These are non-destructive.
The destructive versions of the functions above.
Converts string str to a symbol having the same case as if the
symbol had been read.
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proc must be a procedure of one argument. This procedure calls proc with one argument: a (newly created) output port. When the function returns, the string composed of the characters written into the port is returned.
proc must be a procedure of one argument. This procedure calls proc with one argument: an (newly created) input port from which string’s contents may be read. When proc returns, the port is closed and the value yielded by the procedure proc is returned.
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Returns the index of the first occurence of char within
string, or #f if the string does not contain a
character char.
Returns the index of the last occurence of char within
string, or #f if the string does not contain a
character char.
Searches string to see if some substring of string is equal
to pattern. substring? returns the index of the first
character of the first substring of string that is equal to
pattern; or #f if string does not contain
pattern.
(substring? "rat" "pirate") ⇒ 2 (substring? "rat" "outrage") ⇒ #f (substring? "" any-string) ⇒ 0
Looks for a string str within the first max-no-chars chars of the input port in-port.
When called with two arguments, the search span is limited by the end of the input stream.
Searches up to the first occurrence of character char in str.
Searches up to the first occurrence of the procedure proc returning non-false when called with a character (from in-port) argument.
When the str is found, find-string-from-port? returns the
number of characters it has read from the port, and the port is set to
read the first char after that (that is, after the str) The
function returns #f when the str isn’t found.
find-string-from-port? reads the port strictly
sequentially, and does not perform any buffering. So
find-string-from-port? can be used even if the in-port is
open to a pipe or other communication channel.
Returns a copy of string txt with all occurrences of string old1 in txt replaced with new1, old2 replaced with new2 ….
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This module implements asynchronous (non-polled) time-sliced
multi-processing in the SCM Scheme implementation using procedures
alarm and alarm-interrupt.
Until this is ported to another implementation, consider it an example
of writing schedulers in Scheme.
Adds proc, which must be a procedure (or continuation) capable of
accepting accepting one argument, to the process:queue. The
value returned is unspecified. The argument to proc should be
ignored. If proc returns, the process is killed.
Saves the current process on process:queue and runs the next
process from process:queue. The value returned is
unspecified.
Kills the current process and runs the next process from
process:queue. If there are no more processes on
process:queue, (slib:exit) is called (See section System).
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| 6.3.1 With-File | ’with-file | |
| 6.3.2 Transcripts | ’transcript | |
| 6.3.3 Rev2 Procedures | ’rev2-procedures | |
| 6.3.4 Rev4 Optional Procedures | ’rev4-optional-procedures | |
| 6.3.5 Multi-argument / and - | ’multiarg/and- | |
| 6.3.6 Multi-argument Apply | ’multiarg-apply | |
| 6.3.7 Rationalize | ’rationalize | |
| 6.3.8 Promises | ’promise | |
| 6.3.9 Dynamic-Wind | ’dynamic-wind | |
| 6.3.10 Eval | ’eval | |
| 6.3.11 Values | ’values |
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Description found in R4RS.
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Redefines read-char, read, write-char,
write, display, and newline.
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The procedures below were specified in the Revised^2 Report on
Scheme. N.B.: The symbols 1+ and -1+ are not
R4RS syntax. Scheme->C, for instance, barfs on this
module.
string1 and string2 must be a strings, and start1, start2 and end1 must be exact integers satisfying
0 <= start1 <= end1 <= (string-length string1) 0 <= start2 <= end1 - start1 + start2 <= (string-length string2)
substring-move-left! and substring-move-right! store
characters of string1 beginning with index start1
(inclusive) and ending with index end1 (exclusive) into
string2 beginning with index start2 (inclusive).
substring-move-left! stores characters in time order of
increasing indices. substring-move-right! stores characters in
time order of increasing indeces.
Fills the elements start–end of string with the character char.
≡ (= 0 (string-length str))
Destructively appends its arguments. Equivalent to nconc.
Adds 1 to n.
Subtracts 1 from n.
These are equivalent to the procedures of the same name but without the trailing ‘?’.
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(require 'rev4-optional-procedures)
For the specification of these optional procedures, See Standard procedures in Revised(4) Scheme.
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For the specification of these optional forms, See Numerical operations in Revised(4) Scheme. The two-arg:* forms are
only defined if the implementation does not support the many-argument
forms.
The original two-argument version of /.
The original two-argument version of -.
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For the specification of this optional form, See Control features in Revised(4) Scheme.
The implementation’s native apply. Only defined for
implementations which don’t support the many-argument version.
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The procedure rationalize is interesting because most programming languages do not provide anything analogous to it. For simplicity, we present an algorithm which computes the correct result for exact arguments (provided the implementation supports exact rational numbers of unlimited precision), and produces a reasonable answer for inexact arguments when inexact arithmetic is implemented using floating-point. We thank Alan Bawden for contributing this algorithm.
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Change occurrences of (delay expression) to
(make-promise (lambda () expression)) and (define
force promise:force) to implement promises if your implementation
doesn’t support them
(see Control features in Revised(4) Scheme).
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This facility is a generalization of Common LISP unwind-protect,
designed to take into account the fact that continuations produced by
call-with-current-continuation may be reentered.
The arguments thunk1, thunk2, and thunk3 must all be procedures of no arguments (thunks).
dynamic-wind calls thunk1, thunk2, and then
thunk3. The value returned by thunk2 is returned as the
result of dynamic-wind. thunk3 is also called just before
control leaves the dynamic context of thunk2 by calling a
continuation created outside that context. Furthermore, thunk1 is
called before reentering the dynamic context of thunk2 by calling
a continuation created inside that context. (Control is inside the
context of thunk2 if thunk2 is on the current return stack).
Warning: There is no provision for dealing with errors or
interrupts. If an error or interrupt occurs while using
dynamic-wind, the dynamic environment will be that in effect at
the time of the error or interrupt.
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(require 'eval)
Evaluates expression in the specified environment and returns its
value. Expression must be a valid Scheme expression represented
as data, and environment-specifier must be a value returned by one
of the three procedures described below. Implementations may extend
eval to allow non-expression programs (definitions) as the first
argument and to allow other values as environments, with the restriction
that eval is not allowed to create new bindings in the
environments associated with null-environment or
scheme-report-environment.
(eval '(* 7 3) (scheme-report-environment 5))
⇒ 21
(let ((f (eval '(lambda (f x) (f x x))
(null-environment))))
(f + 10))
⇒ 20
Version must be an exact non-negative integer n
corresponding to a version of one of the Revised^n Reports on
Scheme. Scheme-report-environment returns a specifier for an
environment that contains the set of bindings specified in the
corresponding report that the implementation supports.
Null-environment returns a specifier for an environment that
contains only the (syntactic) bindings for all the syntactic keywords
defined in the given version of the report.
Not all versions may be available in all implementations at all times. However, an implementation that conforms to version n of the Revised^n Reports on Scheme must accept version n. An error is signalled if the specified version is not available.
The effect of assigning (through the use of eval) a variable
bound in a scheme-report-environment (for example car) is
unspecified. Thus the environments specified by
scheme-report-environment may be immutable.
This optional procedure returns a specifier for the environment that contains implementation-defined bindings, typically a superset of those listed in the report. The intent is that this procedure will return the environment in which the implementation would evaluate expressions dynamically typed by the user.
Here are some more eval examples:
(require 'eval)
⇒ #<unspecified>
(define car 'volvo)
⇒ #<unspecified>
car
⇒ volvo
(eval 'car (interaction-environment))
⇒ volvo
(eval 'car (scheme-report-environment 5))
⇒ #<primitive-procedure car>
(eval '(eval 'car (interaction-environment))
(scheme-report-environment 5))
⇒ volvo
(eval '(eval '(set! car 'buick) (interaction-environment))
(scheme-report-environment 5))
⇒ #<unspecified>
car
⇒ buick
(eval 'car (scheme-report-environment 5))
⇒ #<primitive-procedure car>
(eval '(eval 'car (interaction-environment))
(scheme-report-environment 5))
⇒ buick
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values takes any number of arguments, and passes (returns) them
to its continuation.
thunk must be a procedure of no arguments, and proc must be
a procedure. call-with-values calls thunk with a
continuation that, when passed some values, calls proc with those
values as arguments.
Except for continuations created by the call-with-values
procedure, all continuations take exactly one value, as now; the effect
of passing no value or more than one value to continuations that were
not created by the call-with-values procedure is
unspecified.
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| 6.4.1 Repl | Macros at top-level | |
| 6.4.2 Quick Print | Loop-safe Output | |
| 6.4.3 Debug | To err is human ... | |
| 6.4.4 Breakpoints | Pause execution | |
| 6.4.5 Tracing | ’trace | |
| 6.4.6 System Interface | ’system, ’getenv, and ’net-clients |
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Here is a read-eval-print-loop which, given an eval, evaluates forms.
reads, repl:evals and writes expressions from
(current-input-port) to (current-output-port) until an
end-of-file is encountered. load, slib:eval,
slib:error, and repl:quit dynamically bound during
repl:top-level.
Exits from the invocation of repl:top-level.
The repl: procedures establish, as much as is possible to do
portably, a top level environment supporting macros.
repl:top-level uses dynamic-wind to catch error conditions
and interrupts. If your implementation supports this you are all set.
Otherwise, if there is some way your implementation can catch error
conditions and interrupts, then have them call slib:error. It
will display its arguments and reenter repl:top-level.
slib:error dynamically bound by repl:top-level.
To have your top level loop always use macros, add any interrupt catching lines and the following lines to your Scheme init file:
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When displaying error messages and warnings, it is paramount that the output generated for circular lists and large data structures be limited. This section supplies a procedure to do this. It could be much improved.
Notice that the neccessity for truncating output eliminates Common-Lisp’s See section Format (version 3.0) from consideration; even when variables
*print-level*and*print-level*are set, huge strings and bit-vectors are not limited.
qp writes its arguments, separated by spaces, to
(current-output-port). qp compresses printing by
substituting ‘...’ for substructure it does not have sufficient
room to print. qpn is like qp but outputs a newline
before returning. qpr is like qpn except that it returns
its last argument.
*qp-width* is the largest number of characters that qp
should use.
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Requiring debug automatically requires trace and
break.
An application with its own datatypes may want to substitute its own
printer for qp. This example shows how to do this:
Traces (see section Tracing) all procedures defined at top-level in
file ‘file’.
Breakpoints (see section Breakpoints) all procedures defined at
top-level in file ‘file’.
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If your Scheme implementation does not support break or
abort, a message will appear when you (require 'break) or
(require 'debug) telling you to type (init-debug). This
is in order to establish a top-level continuation. Typing
(init-debug) at top level sets up a continuation for
break.
Returns from the top level continuation and pushes the continuation from which it was called on a continuation stack.
Pops the topmost continuation off of the continuation stack and returns an unspecified value to it.
Pops the topmost continuation off of the continuation stack and returns arg1 … to it.
Redefines the top-level named procedures given as arguments so that
breakpoint is called before calling proc1 ….
With no arguments, makes sure that all the currently broken identifiers are broken (even if those identifiers have been redefined) and returns a list of the broken identifiers.
Turns breakpoints off for its arguments.
With no arguments, unbreaks all currently broken identifiers and returns a list of these formerly broken identifiers.
The following routines are the procedures which actually do the tracing when this module is supplied by SLIB, rather than natively. If defmacros are not natively supported by your implementation, these might be more convenient to use.
To break, type
(set! symbol (breakf symbol))
or
(set! symbol (breakf symbol 'symbol))
or
(define symbol (breakf function))
or
(define symbol (breakf function 'symbol))
To unbreak, type
(set! symbol (unbreakf symbol))
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Traces the top-level named procedures given as arguments.
With no arguments, makes sure that all the currently traced identifiers are traced (even if those identifiers have been redefined) and returns a list of the traced identifiers.
Turns tracing off for its arguments.
With no arguments, untraces all currently traced identifiers and returns a list of these formerly traced identifiers.
The following routines are the procedures which actually do the tracing when this module is supplied by SLIB, rather than natively. If defmacros are not natively supported by your implementation, these might be more convenient to use.
To trace, type
(set! symbol (tracef symbol))
or
(set! symbol (tracef symbol 'symbol))
or
(define symbol (tracef function))
or
(define symbol (tracef function 'symbol))
To untrace, type
(set! symbol (untracef symbol))
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If (provided? 'getenv):
Looks up name, a string, in the program environment. If name is
found a string of its value is returned. Otherwise, #f is returned.
If (provided? 'system):
Executes the command-string on the computer and returns the integer status code.
If system is provided by the Scheme implementation, the
net-clients package provides interfaces to common network client
programs like FTP, mail, and Netscape.
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Several Scheme packages have been written using SLIB. There are several reasons why a package might not be included in the SLIB distribution:
Once an optional package is installed (and an entry added to
*catalog*, the require mechanism allows it to be called up
and used as easily as any other SLIB package. Some optional packages
(for which *catalog* already has entries) available from SLIB
sites are:
swissnet.ai.mit.edu:pub/scm/slib-psd1-3.tar.gz ftp.gnu.org:pub/gnu/jacal/slib-psd1-3.tar.gz ftp.maths.tcd.ie:pub/bosullvn/jacal/slib-psd1-3.tar.gz ftp.cs.indiana.edu:/pub/scheme-repository/utl/slib-psd1-3.tar.gz
With PSD, you can run a Scheme program in an Emacs buffer, set breakpoints, single step evaluation and access and modify the program’s variables. It works by instrumenting the original source code, so it should run with any R4RS compliant Scheme. It has been tested with SCM, Elk 1.5, and the sci interpreter in the Scheme->C system, but should work with other Schemes with a minimal amount of porting, if at all. Includes documentation and user’s manual. Written by Pertti Kellom\"aki, pk@cs.tut.fi. The Lisp Pointers article describing PSD (Lisp Pointers VI(1):15-23, January-March 1993) is available as http://www.cs.tut.fi/staff/pk/scheme/psd/article/article.html
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| 7.1 Installation | How to install SLIB on your system. | |
| 7.2 Porting | SLIB to new platforms. | |
| 7.3 Coding Standards | How to write modules for SLIB. | |
| 7.4 Copyrights | Intellectual propery issues. |
More people than I can name have contributed to SLIB. Thanks to all of you.
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<A NAME="Installation"> </A>
Check the manifest in ‘README’ to find a configuration file for your Scheme implementation. Initialization files for most IEEE P1178 compliant Scheme Implementations are included with this distribution.
If the Scheme implementation supports getenv, then the value of
the shell environment variable SCHEME_LIBRARY_PATH will be used
for (library-vicinity) if it is defined. Currently, Chez, Elk,
MITScheme, scheme->c, VSCM, and SCM support getenv. Scheme48
supports getenv but does not use it for determining
library-vicinity. (That is done from the Makefile.)
You should check the definitions of software-type,
scheme-implementation-version,
implementation-vicinity,
and library-vicinity in the initialization file. There are
comments in the file for how to configure it.
Once this is done you can modify the startup file for your Scheme
implementation to load this initialization file. SLIB is then
installed.
Multiple implementations of Scheme can all use the same SLIB directory. Simply configure each implementation’s initialization file as outlined above.
The SCM implementation does not require any initialization file as SLIB support is already built in to SCM. See the documentation with SCM for installation instructions.
SLIB includes methods to create heap images for the VSCM and Scheme48
implementations. The instructions for creating a VSCM image are in
comments in ‘vscm.init’. To make a Scheme48 image for an
installation under <prefix>, cd to the SLIB directory and
type make prefix=<prefix> slib48. To install the image, type
make prefix=<prefix> install48. This will also create a shell
script with the name slib48 which will invoke the saved image.
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If there is no initialization file for your Scheme implementation, you will have to create one. Your Scheme implementation must be largely compliant with IEEE Std 1178-1990, Revised^4 Report on the Algorithmic Language Scheme, or Revised^5 Report on the Algorithmic Language Scheme in order to support SLIB. (2)
‘Template.scm’ is an example configuration file. The comments
inside will direct you on how to customize it to reflect your system.
Give your new initialization file the implementation’s name with
‘.init’ appended. For instance, if you were porting
foo-scheme then the initialization file might be called
‘foo.init’.
Your customized version should then be loaded as part of your scheme
implementation’s initialization. It will load ‘require.scm’ from
the library; this will allow the use of provide,
provided?, and require along with the vicinity
functions (these functions are documented in the section
See section Require). The rest of the library will then be accessible in a
system independent fashion.
Please mail new working configuration files to jaffer @ ai.mit.edu
so that they can be included in the SLIB distribution.
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All library packages are written in IEEE P1178 Scheme and assume that a
configuration file and ‘require.scm’ package have already been
loaded. Other versions of Scheme can be supported in library packages
as well by using, for example, (provided? 'rev3-report) or
(require 'rev3-report) (See section Require).
The module name and ‘:’ should prefix each symbol defined in the
package. Definitions for external use should then be exported by having
(define foo module-name:foo).
Code submitted for inclusion in SLIB should not duplicate routines
already in SLIB files. Use require to force those library
routines to be used by your package. Care should be taken that there
are no circularities in the requires and loads between the
library packages.
Documentation should be provided in Emacs Texinfo format if possible, But documentation must be provided.
Your package will be released sooner with SLIB if you send me a file which tests your code. Please run this test before you send me the code!
Please document your changes. A line or two for ‘ChangeLog’ is
sufficient for simple fixes or extensions. Look at the format of
‘ChangeLog’ to see what information is desired. Please send me
diff files from the latest SLIB distribution (remember to send
diffs of ‘slib.texi’ and ‘ChangeLog’). This makes for
less email traffic and makes it easier for me to integrate when more
than one person is changing a file (this happens a lot with
‘slib.texi’ and ‘*.init’ files).
If someone else wrote a package you want to significantly modify, please try to contact the author, who may be working on a new version. This will insure against wasting effort on obsolete versions.
Please do not reformat the source code with your favorite beautifier, make 10 fixes, and send me the resulting source code. I do not have the time to fish through 10000 diffs to find your 10 real fixes.
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<A NAME="Copyrights"> </A>
This section has instructions for SLIB authors regarding copyrights.
Each package in SLIB must either be in the public domain, or come with a statement of terms permitting users to copy, redistribute and modify it. The comments at the beginning of ‘require.scm’ and ‘macwork.scm’ illustrate copyright and appropriate terms.
If your code or changes amount to less than about 10 lines, you do not need to add your copyright or send a disclaimer.
In order to put code in the public domain you should sign a copyright disclaimer and send it to the SLIB maintainer. Contact jaffer @ ai.mit.edu for the address to mail the disclaimer to.
I, name, hereby affirm that I have placed the software package name in the public domain.
I affirm that I am the sole author and sole copyright holder for the software package, that I have the right to place this software package in the public domain, and that I will do nothing to undermine this status in the future.
signature and date
This wording assumes that you are the sole author. If you are not the sole author, the wording needs to be different. If you don’t want to be bothered with sending a letter every time you release or modify a module, make your letter say that it also applies to your future revisions of that module.
Make sure no employer has any claim to the copyright on the work you are submitting. If there is any doubt, create a copyright disclaimer and have your employer sign it. Mail the signed disclaimer to the SLIB maintainer. Contact jaffer @ ai.mit.edu for the address to mail the disclaimer to. An example disclaimer follows.
If you submit more than about 10 lines of code which you are not placing into the Public Domain (by sending me a disclaimer) you need to:
This disclaimer should be signed by a vice president or general manager of the company. If you can’t get at them, anyone else authorized to license out software produced there will do. Here is a sample wording:
employer Corporation hereby disclaims all copyright interest in the program program written by name.
employer Corporation affirms that it has no other intellectual property interest that would undermine this release, and will do nothing to undermine it in the future.
signature and date, name, title, employer Corporation
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This is an alphabetical list of all the procedures and macros in SLIB.
| Jump to: | -
/
1
<
=
>
A B C D E F G H I K L M N O P Q R S T U V W |
|---|
| Jump to: | -
/
1
<
=
>
A B C D E F G H I K L M N O P Q R S T U V W |
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This is an alphabetical list of all the global variables in SLIB.
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B C D M N P S T |
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B C D M N P S T |
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| Jump to: | A B C D E F G H I L M N O P Q R S T U V W Y |
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How do I know this? I parsed 250kbyte of random input (an e-mail file) with a non-trivial grammar utilizing all constructs.
If you
are porting a Revised^3 Report on the Algorithmic Language Scheme
implementation, then you will need to finish writing ‘sc4sc3.scm’
and load it from your initialization file.
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The buttons in the navigation panels have the following meaning:
| Button | Name | Go to | From 1.2.3 go to |
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where the Example assumes that the current position is at Subsubsection One-Two-Three of a document of the following structure:
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