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CONTENTS
1. Introduction...................................... 1
2. RPL Principles.................................... 2
2.1 Origins..................................... 2
2.2 Mathematical Control........................ 3
2.3 Formal Definitions ......................... 5
2.4 Execution................................... 6
2.4.1 EVAL............................... 8
2.4.2 Data Class Objects................. 9
2.4.3 Identifier Class Objects........... 9
2.4.4 Procedure Class Objects............ 10
2.4.5 Object Skipover and SEMI........... 10
2.4.6 RPL Pointers....................... 11
2.5 Memory Management........................... 11
2.6 User RPL and System RPL..................... 13
2.7 Programming in System RPL................... 14
2.8 Sample RPL Program.......................... 16
2.8.1 The Source File.................... 16
2.8.2 Compiling the Program.............. 18
3. Object Structures................................. 19
3.1 Object Types................................ 19
3.1.1 Identifier Object.................. 19
3.1.2 Temporary Identifier Object........ 19
3.1.3 ROM Pointer Object................. 20
3.1.4 Binary Integer Object.............. 20
3.1.5 Real Number Object................. 20
3.1.6 Extended Real Number Object........ 21
3.1.7 Complex Number Object.............. 22
3.1.8 Extended Complex Number
Object............................. 22
3.1.9 Array Object....................... 23
3.1.10 Linked Array Object................ 23
3.1.11 Character String Object............ 25
3.1.12 Hex String Object.................. 25
3.1.13 Character Object................... 25
3.1.14 Unit Object........................ 26
3.1.15 Code Object........................ 26
3.1.16 Primitive Code Object.............. 27
3.1.17 Program Object..................... 27
3.1.18 List Object........................ 28
3.1.19 Symbolic Object.................... 28
3.1.20 Directory Object................... 29
3.1.21 Graphics Object.................... 29
3.2 Terminology and Abbreviations............... 30
4. Binary Integers................................... 32
4.1 Built-in Binary Integers.................... 32
4.2 Binary Integer Manipulation................. 34
4.2.1 Arithmetic Functions............... 34
4.2.2 Conversion Functions............... 35
5. Character Constants............................... 36
6. Hex & Character Strings........................... 37
- i -
6.1 Character Strings........................... 37
6.2 Hex Strings................................. 39
7. Real Numbers...................................... 41
7.1 Built-in Reals.............................. 41
7.2 Real Number Functions....................... 41
8. Complex Numbers................................... 46
8.1 Built-in Complex Numbers.................... 46
8.2 Conversion Words............................ 46
8.3 Complex Functions........................... 46
9. Arrays............................................ 48
10. Composite Objects................................. 49
11. Tagged Objects.................................... 51
12. Unit Objects...................................... 52
13. Temporary Variables and Temporary
Environments...................................... 54
13.1 Structure of the Temporary Environment
Area........................................ 55
13.2 Named vs. Unnamed Temporary Variables....... 57
13.3 Provided Words for Temporary Variables...... 59
13.4 Coding Suggestions.......................... 60
14. Checking Arguments................................ 61
14.1 Number of Arguments......................... 62
14.2 Dispatching on Argument Type................ 63
14.3 Examples.................................... 66
15. Loop Control Structures........................... 68
15.1 Indefinite Loops............................ 68
15.2 Definite Loops.............................. 70
15.2.1 Provided Words..................... 70
15.2.2 Examples........................... 71
16. Error Generation & Trapping....................... 73
16.1 Trapping: ERRSET and ERRTRAP................ 73
16.2 Action of ERRJMP............................ 73
16.3 The Protection Word......................... 74
16.4 Error Words................................. 75
17. Test and Control.................................. 76
17.1 Flags and Tests............................. 76
17.1.1 General Object Tests............... 77
17.1.2 Binary Integer Comparisons......... 78
17.1.3 Decimal Number Tests............... 79
17.2 Words that Operate on the Runstream......... 80
17.3 If/Then/Else................................ 83
17.4 CASE words.................................. 84
18. Stack Operations.................................. 87
19. Memory Operations................................. 89
19.1 Temporary Memory............................ 89
- ii -
19.2 Variables and Directories................... 89
19.2.1 Directories........................ 91
19.3 The Hidden Directory........................ 92
19.4 Additional Memory Utilities................. 93
20. Display Management & Graphics..................... 94
20.1 Display Organization........................ 94
20.2 Preparing the Display....................... 95
20.3 Controlling Display Refresh................. 96
20.4 Clearing the Display........................ 97
20.5 Annunciator Control......................... 97
20.6 Display Coordinates......................... 98
20.6.1 Window Coordinates................. 98
20.7 Displaying Text............................. 99
20.7.1 Standard Text Display Areas........ 99
20.7.2 Temporary Messages................. 101
20.8 Graphics Objects............................ 102
20.8.1 Warnings........................... 102
20.8.2 Graphics Tools..................... 103
20.8.3 Grob Dimensions.................... 104
20.8.4 Built-in Grobs..................... 104
20.8.5 Menu Display Utilities............. 105
20.9 Scrolling the Display....................... 105
21. Keyboard Control.................................. 109
21.1 Key Locations............................... 109
21.2 Waiting for a Key........................... 110
21.3 InputLine................................... 111
21.3.1 InputLine Example.................. 112
21.4 The Parameterized Outer Loop................ 113
21.4.1 The Parameterized Outer Loop
Utilities.......................... 114
21.4.2 Overview of the Parameterized
Outer Loop......................... 115
21.4.3 Handling Errors with the
Utilities.......................... 116
21.4.4 The Display........................ 116
21.4.5 Error Handling..................... 117
21.4.6 Hard Key Assignments............... 117
21.4.7 Menu Key Assignments............... 119
21.4.8 Preventing Suspended
Environments....................... 120
21.4.9 Specifying an Exit Condition....... 120
21.4.10 ParOuterLoop Example............... 121
22. System Commands................................... 123
- iii -
RPL PROGRAMMING GUIDE
1. Introduction
The HP 48 calculator was designed to be a customizable
mathematical scratchpad for use by students and
professionals in technical fields. In many respects it is a
descendent of the HP 41, providing a much broader and more
sophisticated computation capability than the HP 41, but
preserving its RPN/key-per-function orientation.
The HP 48 uses the so-called Saturn architecture, named by
the code name of the original CPU designed for the HP 71B
handheld computer. It also uses a custom operating
system/language called RPL, which was designed to provide
symbolic mathematical capabilities, executing from ROM in a
limited RAM environment (it is today still the only symbolic
system that can run in ROM). The combination of specialized
hardware and firmware makes it relatively difficult to
develop application software for the HP48, and accordingly
the HP48 is not positioned as a primary external application
vehicle. The orientation of the product and its user
programming language is towards simple customization by the
primary user.
Despite these barriers, the price and physical configuration
of the HP48 make it a desirable application platform for
many software developers, especially those who want to
target customers in the HP48's normal markets. The user
language is suitable for simple programs, but for elaborate
systems, the intentional error protection and other overhead
can result in substantial performance penalties compared
with the programs using the full range of system calls.
In this document, we will provide a description of the
design and conventions of the RPL language. The material
here should provide enough detail to permit the creation of
RPL programs and other objects, using the associated IBM
PC-based compilation tools. Included is documention of a
large number of system RPL objects that are useful utilities
for program development.
Page 1
2. RPL Principles
(The following material was excerpted from "RPL: A
Mathematical Control Language", by W. C. Wickes, published
in "Programming Environments", Institute for Applied Forth
Research, Inc., 1988)
2.1 Origins
In 1984, a project was started at Hewlett-Packard Corvallis
Division to develop a new software operating system to
streamline calculator development and support a new
generation of hardware and software. Previously, all HP
calculators were implemented entirely in assembly language,
a process that was becoming increasingly cumbersome and
inefficient as the memory sizes of the calculators
increased. The objectives for the new operating system were
as follows:
+ To provide execution control and memory management,
including plug-in memory;
+ To provide a programming language for rapid prototyping
and application development;
+ To support a variety of business and technical
calculators;
+ To execute identically out of RAM and ROM;
+ To minimize memory use, especially RAM;
+ To be transportable to various CPU's;
+ To be extensible; and
+ To support symbolic mathematical operations.
Several existing operating systems and languages were
considered, but none could meet all of the design
objectives. A new system was therefore developed, which
merges the threaded interpretation of Forth with the
functional approach of Lisp. The resulting operating
system, known unofficially as RPL (for Reverse-Polish Lisp),
made its first public appearance in June of 1986 in the HP-
18C Business Consultant calculator. Subsequently, RPL has
been the basis for the HP-17B, HP-19B, HP-27S, HP-28C and
HP-28S, and HP 48S and HP 48SX calculators. The HP-17B,
18C, and 19B are designed for business applications; they
and the HP-27S scientific calculator offer an ``algebraic''
calculating logic, and the underlying operating system is
invisible to the user. The HP 28/HP 48 families of
scientific calculators use an RPN logic, and many of the
facilities of operating system are directly available as
calculator commands.
Page 2
2.2 Mathematical Control
The official operating system objectives listed above were
blended throughout the RPL development cycle with a less
formal objective of creating a mathematical control language
that would extend the ease-of-use and interactive nature of
a calculator to the realm of symbolic mathematical
operations. A calculator is distinguished from a computer
in this context by:
+ very compact size;
+ ``instant on''--no warm-up or software
loading/bootstrapping;
+ dedicated keys for common operations rather than qwerty
keyboards.
+ ``instant action'' when a function key is pressed.
The HP-28, which was developed by the same team that created
the RPL operating system, was the first realization of this
background objective; the HP 48 is the latest and most
mature implementation.
Much of the design of RPL can be derived from a
consideration of the manner in which ordinary mathematical
expressions are evaluated. Consider, for example, the
expression
1+ 2 sin(3x) +4
As any RPN enthusiast knows, the expression as written here
does not correspond in its left-to-right order to the order
in which a human or a machine could actually carry out the
calculation. For example, the first sum has to be delayed
until after several other steps are executed. Rewriting the
expression in RPN form, we obtain a representation that is
also executable in its written order:
1 2 3 x * sin * + 4 +
To translate this sequence into a control language, we need
to formalize several concepts. First, we use the generic
term object to refer to each step in the sequence, such as
1, 2, or sin. Even in this simple example, there are three
classes of objects:
1. Data objects. Execution of an object such as 1, 2, or
3 in the example just returns the value of the object.
2. Names. The symbol x must be the name of some other
object; when x is executed, the named object is
substituted for the symbol.
Page 3
3. Procedures. Objects such as *, sin, and + represent
mathematical operations, which are applied, for
example, to data objects to create new data objects.
The concept of an object is closely tied to the concept of
execution, which can be thought of as the "activation" of an
object. An individual object is characterized by its object
type, which determines its action when executed, and its
value, which distinguishes it from another of the same type.
Expression evaluation in these terms becomes the sequential
execution of a series of objects (the objects representing
the RPN form of the expression). Two constructs are
necessary to make the execution coherent: an object stack
and an interpreter pointer. The first construct provides a
place from which procedure objects can take their arguments
and to which they can return their result objects. A LIFO
stack as used in Forth is ideal for this purpose, and such a
stack is included in RPL. The interpreter pointer is just a
program counter that indicates the next object to be
executed. The interpreter pointer should be distinguished
from the CPU program counter, which indicates the next CPU
instruction.
A mathematical expression considered as a sequence of
objects suggests an additional classification of objects as
either atomic or composite. An atomic objects is an object
that cannot be taken apart into stand-alone objects;
examples are a simple data object like 1 or 2, or perhaps an
object like * or + that is implemented normally in assembly
language. A composite object is a collection of other
objects. In Forth, a secondary word is an example of a
composite object. RPL provides at least three types of
composite objects: secondaries, which are prcedures defined
as unrestricted sequences of objects; symbolics, which are
sequences of objects that must be logically equivalent to
algebraic expressions; and lists, which contain objects
collected for any logical purpose other than sequential
execution.
The final point in this brief mathematics-to-RPL derivation
is the observation that the definition of composite objects
leads to the concepts of threaded interpretation and a
return stack. That is, in the example it it easy to imagine
that the name object x could represent a composite object
that in turn represents another expression. In that case,
one would expect execution of x to cause the intepreter
pointer to jump to the sequence of objects referenced by x,
while the location of the object following x in the original
is stored so that execution can later return there. This
process should be able to be indefinitely repeated, so RPL
provides a LIFO stack for the return objects.
The preceding introduction might in some respects also have
been an introduction for the derivation of Forth, if
questions of floating-point versus integer arithmetic are
Page 4
ignored. In particular, both systems use threaded
interpretation and a LIFO data stack for interchange of
objects. However, there are several important differences
between Forth and RPL:
+ RPL supports both direct and indirect threaded
execution in a completely uniform manner.
+ RPL supports dynamic allocation of its objects.
+ RPL code is, in general, completely relocatable.
2.3 Formal Definitions
This section will present the abstract definitions of RPL
that are independent of any particular CPU or
implementation.
The fundamental structure in RPL is the object. Any object
consists of a pair: the prologue address and the object
body.
+---------------+
| -> Prologue |
+---------------+
| Body |
+---------------+
The two parts are contiguous in memory with the prologue
address part in lower memory The prologue address is that of
a machine-code routine that executes the object; the body is
data used by the prologue. Objects are classified by type;
each type is associated with a unique prologue. The
prologues thus serve a dual purposes of executing an object
and identifying its type.
An object is either atomic or composite. A composite object
is either null or non-null; a non-null composite has a head
which is an object and a tail which is composite.
In addition to being executed, all RPL objects can be
copied, compared, embedded in composite objects, and
skipped. The latter property implies that the memory length
of any object is predetermined or can be computed from the
object. For atomic objects such as real numbers, the size
is invariant. For a more complicated atomic object such as
a numerical array, the size can be computed from the array
dimensions that are stored in the body of the array object.
(RPL arrays are not composite--the elements do not have
individual prologues and hence are not objects.) Composite
objects may include a length field or they may end with a
marker object.
A pointer is an address in the memory space of the CPU, and
may be a location pointer or an object pointer. A location
pointer addresses any part of memory, whereas a object
pointer point to an object, specifically to the prologue
location pointer at the start of an object.
Page 5
RPL requires, in addition to the CPU program counters, five
variables for its fundamental operation:
+ The interpreter pointer I.
+ The current object pointer O.
+ The data stack pointer D.
+ The return stack pointer R.
+ The amount of free memory M.
In the most general definition of RPL, I is an object
pointer pointing to a composite object that is the top of a
stack of composite objects called the runstream. R points
to the rest of the runstream stack. In practical
implementations, this definition is streamlined by allowing
I to point to any object embedded in a composite, while R is
a location pointer pointing to the top of a stack of object
pointers, each of which points to an embedded object.
It is fundamental to RPL that objects can be executed
directly or indirectly with equivalent results. This means
that an object can be represented anywhere by a pointer to
the object as well as by the object itself.
2.4 Execution
RPL object execution consists of the CPU execution of the
object's prologue, where the prologue code can access the
object's body by means of the object pointer O. Object
pointer execution is the CPU execution of the pointer's
addressee. This interpretive execution is controlled by the
inner interpreter, or inner loop, which determines the
sequence of object/object pointer execution.
RPL objects are sorted by their general execution properties
into three classes:
* Objects that merely return themselves to the data stack
when executed are called data class objects. Examples are
real numbers, strings, and arrays.
* Objects that serve as references for other objects are
called identifier class objects. RPL defines three
identifier class object types: identifier (global name),
temporary identifier (local name), and ROM pointer (XLIB
name).
* Objects that contain bodies into which execution flow can
pass are called procedure class objects. There are three
types of procedure class objects: programs (also called a
"secondaries" or a "colon-definitions" in Forth
terminology), code objects, and primitive code objects.
Page 6
The RPL inner loop and prologue designs provide for
interchangeable direct and indirect object execution (note:
a patent application has been filed for the concepts
described next). The inner loop consists of the following
pseudo-code:
O = [I]
I = I + delta
PC = [O] + delta
where [x] means the contents of address x, and delta is the
length of a memory address. This loop is the same in Forth,
except that the CPU execution jumps to [O]+delta instead of
to [O]. This is because all RPL prologues start with their
own address, which is the feature that makes possible direct
execution as well as indirect. Prologues look like this:
PROLOG ->PROLOG Self address
IF O + delta != PC THEN GOTO REST Test for direct execution
O = I - delta Correct O
I = I + len Correct I
REST (rest of prologue)
Here len is the length of the object body.
When an object is being executed directly, the inner loop
does not set O or I correctly. However, a prologue knows it
is being executed directly by comparing the PC address with
O and can update the variables accordingly. A prologue is
also responsible for preserving the threaded interpretation
by including a return to the inner loop at its end.
This flexible interpretation is intrinsically slower than
the indirect-only execution (like Forth), because of the
overhead of making the direct/indirect test. In practical
implementations of RPL, it is possible to shift the overhead
almost entirely to the direct execution case, so that the
execution penalty for the indirect case is negligible,
including primitive assembly language objects that are never
executed directly. The trick is to replace the last step of
the inner loop with the Forth-like PC = [O], and, for
prologues of directly-executable objects, replace the self-
address at the start of each prologue with a slice of
executable code delta in length. The compiled opcodes of
this slice must also be the address of a meta-prologue that
handles the direct execution case. In Saturn CPU
implementations, the code slice consists of the instruction
M=M-1 (decrementing available memory is common to virtually
all directly-executable object prologues) plus a NOP
instruction to fill out the delta length.
The virtue of direct execution is that it enables the
straightforward management of nameless objects that are
created during execution. During the course of symbolic
algebraic manipulations, it is common to create, use, and
discard any number of temporary intermediate results; the
Page 7
necessity to compile and store these objects with some form
of name for indirect reference, then uncompile them to
recover memory, would make the whole process unmanageable.
In RPL such objects can be placed on the stack, copied,
embedded in composite objects, executed, and deleted. For
example, a composite object representing the expression x +
y can be added to a second object representing 2z, returning
the result object x + y + 2z; furthermore, any of these
objects could be embedded in a program object to perform the
addition repetitively.
Although RPL is primarily a syntax-less postfix language in
which procedures take their arguments from the stack and
return results to the stack, it does provide operations that
work on the runstream to provide for prefix operations and
for alterations to the normal threaded execution. Foremost
among the runstream operations is the quoting operation that
takes the next object from the runstream and pushes it on
the data stack to postpone its execution. This operation is
similar in purpose to the Lisp QUOTE, but takes its RPL name
' (tick), from its Forth equivalent. RPL also has operations
to push and pop objects from the return stack. (DO loop
parameters, however, are not stored on the return stack,
using a special environment instead.)
2.4.1 EVAL An object on the data stack may be indirectly
executed by means of the RPL word EVAL, which pops an object
from the stack and executes its prolog. The system object
EVAL should be distinguished from the user RPL command EVAL.
The latter is equivalent to system EVAL except for lists,
symbolic objects, and tagged objects. For a tagged object,
user EVAL executes the object contained in the body of the
tagged object. For lists and symbolics, user EVAL
dispatches to the system word COMPEVAL, which executes the
object as if it were a program (see below).
Page 8
2.4.2 Data_Class_Objects Object types in this class are:
Binary Integer Object (note: the user RPL binary integer is actually
a hex string object in system RPL terms.)
Real Object
Extended Real Object
Complex Object
Extended Complex Object
Array Object
Linked Array Object
Character String Object
Hex String Object
Character Object
Graphics Object
Unit Object
List Object
Symbolic Object ("algebraic object")
Library Data Object
Directory Object
Tagged Object
External Object
All objects in the data class have the property that, when
executed, they simply place themselves on the top of the
data stack.
2.4.3 Identifier_Class_Objects Object types in this class
are:
ROM Pointer Object (XLIB name)
Identifier Object (global name)
Temporary Identifier Object (local name)
Objects in the identifier class share the property that they
serve to provide references for other objects. Identifier
objects represent the resolution of global variables, and
ROM Pointer Objects represent the resolution of commands
stored in libraries. Temporary identifier objects, on the
other hand, provide references for temporary objects in
temporary environments.
Execution of a ROM pointer object (by the DOROMP prologue)
entails locating and then executing the referenced ROM-WORD
object part. Non-location is an error condition.
Execution of an identifier object (by the DOIDNT prologue)
entails locating and then executing the referenced global
variable object part. Non-location returns the identifier
object itself.
Execution of a temporary identifier object (by the DOLAM
prologue), entails locating the referenced temporary object
and pushing it on the data stack. Non-location is an error
condition.
Page 9
2.4.4 Procedure_Class_Objects Object types in this class
are:
Code Object
Primitive Code Object
Program Object
Objects in the procedure class share the property of
executability, that is, executing a procedure class object
involves passing control to executable procedure or code
associated with the object.
Code objects contain assembly language sequences for direct
execution by the CPU, but are otherwise normal, relocatable
objects. Primitive code objects have no prolog in the usual
sense; the prolog address field points directly to the
object body, which contains an assembly language sequence.
These objects can only exist in permanent ROM, and can never
be executed directly. When a code object or primitive code
object is executed, control is passed (by setting the PC) to
the machine language instruction set contained in the object
body. For a primitive code object, this control passing is
done by the execution mechanism (EVAL or the inner loop)
itself. For a code object, the prologue passes control by
placing the PC at the beginning of the machine language
slice contained in the object body. Note again that a
primitive code object prologue (which is its body) need not
contain logic to test for direct verses indirect execution
(nor contain code to update I or O) since, by definition, it
is never executed directly.
Execution of a program is sequential execution of the
objects and object pointers that comprise the body of the
program. The execution is threaded in that the objects in a
program may themselves be secondaries or pointers to
secondaries. When encountered by the inner loop, an
embedded program is executed prior to resumption of
execution of the current one.
The end of a program is marked by the object SEMI (from
"semicolon"--a ";" is the closing delimiter recognized by
the RPL compiler to mark the end of a program definition).
Execution of SEMI pops the top object pointer from the
return stack and resumes execution at that point.
2.4.5 Object_Skipover_and_SEMI One of the basic premises
of RPL is that any RPL object that can be directly executed
(which includes all object types except primitive code
objects) must be traversable, that is, must have a structure
which allows it to be skipped over. Object skipover occurs
throughout the RPL system but most notably during direct
execution by the inner loop when the interpreter pointer I
must be set to point to the next object after the one being
directly executed.
Page 10
There exist both RPL objects and utilities to perform this
object skipover function. In addition, objects are required
to skipover themselves when being executed directly. The
skipover mechanism for atomic objects is simple and
straightforward since the object length is either known or
is easily computable. For the composite objects (program,
list, unit, symbolic) the length is not easily computable
and the skipover function here is somewhat more involved,
using an implicit recursion. These composite objects do not
carry known or easily computable length information and
therefore must have a tail delimiter, namely an object
pointer to the primitive code object SEMI. Note that SEMI
serves an explicit function for the program object (the
procedure class composite object); for data class composite
objects (list, unit, and symbolic objects), it only serves
as a tail delimiter.
2.4.6 RPL_Pointers A pointer is defined to be an address
and may be either a location pointer or an object pointer. A
location pointer addresses any segment of the memory map
while an object pointer specifically addresses an object.
Note that, for example, the prologue address part of an
object is a location pointer.
2.5 Memory Management
The uniformity of direct and indirect execution means not
only that objects as well as object pointers can be embedded
in the execution stream, but also that object pointers can
logically replace objects. In particular, the RPL data and
return stacks explicitly are stacks of object pointers.
This means, for example, that an object on the data stack
can be copied (e.g. by DUP) at a cost of only delta bytes of
memory, regardless of the size of the object. Furthermore,
duplication and similar stack operations are very fast.
Of course, the objects referenced on the stacks must exist
somewhere in memory. Many, including all of the system
objects that provide system management and an application
language, are defined in ROM and can be referenced by a
pointer with no other housekeeping implications. Objects
created in RAM may exist in two places. Those that are
unnamed are stored in a temporary object area, where each is
maintained as long as it is referenced by a pointer anywhere
in the system (this implies that if a temporary object
moves, all pointers to it must be updated). Naming an
object consists of storing it as a pair with a name field in
a linked-list called the user object area. These objects
are maintained indefinitely, until they are explicitly
purged or replaced. A named object is accessed by means of
an identifier object, which consists of an object with a
name field as its body. Executing an identifier causes the
user object area to be searched for an object stored with
the same name, which is then executed. This run-time
Page 11
resolution is intrinsically slower than the compile-time
resolution used for ROM objects, but it allows for a dynamic
and flexible system where the order in which objects are
compiled is immaterial.
The process of naming objects by storing them with names in
the user object area is augmented by the existence of local
environments, in which objects can be bound to names (lambda
variables) that are local to a currently executing
procedure. The binding is abandoned when the procedure
completes execution. This feature simpifies complicated
stack manipulations by allowing the stack objects to be
named and then referenced by name within the scope of a
defining procedure.
RPL provides that any object stored in the user object area
can be deleted without corrupting anything in the system.
This requires certain design conventions:
+ When a RAM object is stored in the user object area, a
new copy of the object is stored, not a pointer to the
object.
+ Pointers to RAM objects are not permitted in composite
objects. When a composite object is created from stack
objects, RAM objects are copied and directly embedded
in the composite. When a stored object is represented
by name in a composite, it is the identifier object
that is embedded, not a location pointer as in Forth.
+ If a stored object is referenced by any pointers on the
stacks at the time when it is purged, it is copied to
the temporary object area and the pointers to it are
updated accordingly. This means that the memory
associated with an object is not recovered until the
last reference to it is deleted.
The use of temporary objects with multiple references means
that a temporary object can not necessarily be deleted from
memory immediately when a single reference to it is
eliminated. In current RPL implementations, no memory
recovery at all is performed until the system runs out of
memory (M=0), at which time all unreferenced objects in the
temporary object area are deleted. The process, called
"garbage collection" can be significantly time-consuming, so
that RPL execution does not proceed uniformly.
From the preceding discussion, it will be apparent that RPL
is not as fast in general as Forth because of its extra
interpretation overhead and greatly elaborated memory
management scheme. While maximum execution speed is always
desirable, the design of RPL emphasizes its role as an
interactive mathematical control language in which
flexibility, ease of use, and the ability to manipulate
procedural information are paramount. In many cases, these
attributes of RPL result in faster problem-solving
Page 12
throughput than Forth, which executes faster but is more
difficult to program.
RPL also provides for objects that are intermediate between
those fixed in ROM and those that are mobile in RAM. A
library is a collection of objects, organized in a permanent
structure that permits parse-time and run-time resolution by
means of tables included in the library. An XLIB name is an
identifier class object that contains a library number and
an object number within the library. Execution of an XLIB
name executes the stored object. The identities and
locations of libraries are determined at system
configuration. A particular library can be associated with
its own RAM directory, so that, for example, a library might
contain permanent formulas for which the variable values are
maintained in RAM.
2.6 User RPL and System RPL
There is no fundamental difference between the HP 48
programming language, which we will call "user RPL," and the
"system RPL" in which HP 48 functionality is implemented.
User language programs are executed by the same inner loop
interpreter as system programs, with the same return stack.
The data stack displayed on the HP 48 is the same as that
used by system programs. The distinction between user RPL
and system RPL is only one of scope: user RPL is a subset of
system RPL. User RPL does not provide direct access to all
of the data class object types that are available; the use
of built-in procedures is limited to those that are provided
as commands.
A "command" is procedure-class object stored in a library,
along with a text string that serves as the command's name.
The name is used for compiling and decompiling the object.
When the command line parser matches text in the command
line with a command name, it compiles an object pointer if
the command is contained in a library in the HP 48's
permanent ROM. Otherwise it compiles the corresponding XLIB
name. Also, built-in command objects are preceded in ROM by
a six-nibble field that is the body of an XLIB name. When
the decompiler encounters an object pointer, it looks for
this field in the ROM ahead of the object; if it finds a
valid field, it then uses the information there to locate a
text command name to display. Otherwise, it decompiles the
object itself.
Commands are distinguished from other procedure objects by
certain conventions in their design. Structurally, all
commands are program objects, the first object in which is
one of the system dispatch objects CK0, CK1&Dispatch,
CK2&Dispatch, CK3&Dispatch, CK4&Dispatch, and CK5&Dispatch
(see section 13). CK0, which is used by zero-argument
commands, may be followed by any additional objects.
CK1&Dispatch ... CK&Dispatch must be followed by a sequence
Page 13
of pairs of objects; the first of each pair identifies a
stack argument type combination, and the second specifies
the object to execute for each corresponding combination.
The last pair is followed by the end-program marker object
(SEMI).
The other command object conventions govern their behavior.
In particular, they should:
* remove any temporary objects from the stack, returning
only the specified results;
* do any range checking necessary to ensure that errors do
not occur that might cause disasters;
* restore HP48 modes to their original states, unless the
command is specifically for changing a mode.
The overhead involved in these structure and behavior
conventions does impose a minor performance penalty.
However, the primary execution speed advantage of system RPL
over user RPL comes simply from the larger set of available
procedures in system RPL, access to fast binary arithmetic,
and improved control over system resources and execution
flow.
2.7 Programming in System RPL
Writing programs in system RPL is no different in principle
than in user RPL; the difference lies in the syntax and
scope of the compiler. For user RPL, the compiler is the
command line ENTER, the logic of which is documented in the
owners' manuals. For system RPL developed on a PC, the
compiler has several parts. The immediate analog of the
command line parser is the program RPLCOMP, which parses
source code text into Saturn assembly language. (The syntax
used by RPLCOMP is described in xxx.) The output of RPLCOMP
is passed to the assembler program SASM, which produces
assembled object code. The program SLOAD resolves symbol
references in SASM's output, finally returning executable
code suitable for downloading into the HP 48. Individual
objects can be collected in an HP 48 directory that is
transferred back to the PC, where the program USRLIB can
transform the directory into a library object. (It would be
desirable to create a library directly on the PC, but the
program to do this is not available at present.)
For the purpose of illustration, consider a hypothetical
project development process that will result in a library
object constructed with the USRLIB tool. The library is to
contain a single command, BASKET, which calculates basket
weaving factors according to several input parameters.
BASKET should be designed with the structure described above
for commands. In addition, assume that BASKET calls several
other programs which are not to be user-accessible. To
Page 14
achieve this, the objects are compiled on the PC, then
downloaded into the HP 48 in a common directory, stored as
BASKET, B1, B2, ... , where the latter variables contain the
subroutines. The directory is uploaded to the PC, where
USRLIB is applied to it with the directive that B1, B2, ...
are to be "hidden."
There is no requirement that a program produced with the RPL
compiler must be presented in a library object - if the
entire application can be written within a single program,
then so much the better. As programs grow beyond some
reasonable level of complexity, this becomes more difficult,
and a library object approach with multiple variables
becomes easier to manage.
1. Create the source file on the PC using your favorite
editor. The program source file name should have a
".s" extension, such as "prog.s". Use the compiler
RPLCOMP.EXE to produce the Saturn assembler source
file "prog.a".
2. Use the Saturn assembler SASM.EXE to assemble the
program and produce an output file "prog.o".
3. Use the Saturn loader SLOAD.EXE to resolve your
program's calls to HP 48 operating system. SLOAD.EXE
output files may have any name, but the ".ol"
extension is often used.
4. Download the final file (use binary transfer!) to the
HP 48, and try out your code.
5. Upload the directory containing one or more objects to
the PC, and use USRLIB.EXE to convert it to a library.
Page 15
2.8 Sample RPL Program
To get acquainted with the process of producing a program
written in internal RPL, consider the following example,
which we'll call TOSET.
2.8.1 The_Source_File
This program removes duplicate objects from a list by
decomposing the list into a series of objects on the stack,
creating a new empty list, and putting the stack objects
into the new list if they're unique.
* ( {list} --> {list}' )
ASSEMBLE
NIBASC /HPHP48-D/
RPL
::
CK1NOLASTWD ( *Req. 1 argument* )
CK&DISPATCH0 list
::
DUPNULL{}? ?SEMI ( *Exit for empty list* )
INNERCOMP ( objn ... obj1 #n )
reversym ( obj1 ... objn #n )
NULL{} SWAP ( obj1 ... objn {} #n )
ZERO_DO (DO)
SWAP ( obj1 ... objn-1 {} objn )
apndvarlst ( obj1 ... objn-1 {}' )
LOOP
;
;
The first line is a comment, showing the input and output
conditions for the program. Comments are denoted by an
asterisk (*) in the first column, or within parentheses.
Every programmer has their own style for comments. The style
shown here is that objects are shown with stack level one on
the right. Text is enclosed in asterisks.
The sequence
ASSEMBLE
NIBASC /HPHP48-D/
RPL
is a command to the assembler that includes the header for
binary data transfer from the PC to the HP48. This is
included here for simplicity, but could be included from
another file by the loader.
The first command, CK1NOLASTWD, requires the stack contain
at least one item, and clears the ram location which stores
the name of the current command. This is important, because
Page 16
you don't want to attribute errors encountered in this
program to the last function that generated an error.
The second command, CK&DISPATCH0, reads a structure of the
form
type action
type action
...
to decide what action to take based on the TYPE of object
presented. If the type of object in level 1 does not have
an entry in the table, the error "Bad Argument Type" will be
generated. In this example, only one type of argument, a
list, is acceptable, and the corresponding action is a
secondary. For more on argument checking commands, see the
chapter "Argument Validation".
The command DUPNULL{}? returns the list and a TRUE/FALSE
flag which indicates if the list is empty. The command
?SEMI exits the secondary if the flag is TRUE.
The command INNERCOMP is an internal form of the user word
LIST->. The number of objects is returned in level one as a
binary integer (see the chapter "Binary Integers").
The command "reversym" reverses the order of #n objects on
the stack. This is used here to account for the ordering of
objects placed in a list by the "apndvarlst" which is
described below.
The ZERO_DO command begins a counted loop. This loop will
process each object in the original list. The (DO) command
tells RPLCOMP that this is the start of a loop, otherwise
the LOOP command would be flagged as unmatched.
The "apndvarlst" command appends an object to a list if and
only if that object does not appear in the list already.
The LOOP command ends the loop. For more on loop commands,
see the chapter "Loop Structures".
Page 17
2.8.2 Compiling_the_Program To compile the program for the
HP 48, follow these steps:
1. Store the example code in a file TOSET.S.
2. RPLCOMP TOSET.S TOSET.A
This command compiles the RPL source and produces a
Saturn assembler source file.
3. SASM TOSET.A
This command assembles the Saturn source file to
produce the files TOSET.L and TOSET.O.
4. The file TOSET.M is a loader control file that looks
like this:
TITLE Example <-- Specifies a listing title
OUTPUT TOSET <-- Specifies the output file
LLIST TOSET.LR <-- Specifies the listing file
SUPPRESS XREF <-- Suppresses the cross ref
SEARCH ENTRIES.O <-- Reads HP48 entries
REL TOSET.O <-- Loads TOSET.o
END
Create the file TOSET.M and invoke the loader:
SLOAD -H TOSET.M
Check the file TOSET.LR for errors. An unresolved reference
usually points to a misspelled command. Now download the
file TOSET into the HP 48 and give it a try!
Enter the list { 1 2 2 3 3 3 4 }, evaluate TOSET, and you
should get { 1 2 3 4 }.
Page 18
3. Object Structures
This chapter provides additional information about some of
the RPL object types supported by the HP 48. Although the
information is primarily relevant to assembly language
programming, a knowledge of object structure can often help
in understanding performance and efficiency issues in RPL
programming.
Unless explicitly stated otherwise, all specifically-defined
fields within an object body are assumed to be 5 nibbles,
the CPU address width.
3.1 Object Types
3.1.1 Identifier_Object
An identifier object is atomic, has the prologue DOIDNT, and
a body which is an ID Name form.
+---------------+
| -> DOIDNT | Prologue Address
+---------------+ Identifier
| ID NAME FORM | Body Object
+---------------+
An ID name form is a character sequence preceded by a one-
byte character count field.
Identifier objects are, among other things, the compiletime
resolution of global variables.
3.1.2 Temporary_Identifier_Object
A temporary identifier object is atomic, has the prologue
DOLAM, and a body which is an ID name form.
+---------------+
| -> DOLAM | Prologue Address Temporary
+---------------+ Identifier
| ID NAME FORM | Body Object
+---------------+
Temporary identifier objects provide named references for
temporary objects bound to the identifiers in the formal
parameter list of a temporary variable structure.
Page 19
3.1.3 ROM_Pointer_Object
A ROM pointer object, or XLIB name, is atomic, has the
prologue DOROMP, and a body which is a ROM-WORD identifier.
+------------------+
| -> DOROMP | Prologue Address
+------------------+ ROM
| | Pointer
| Command | Body Object
| Identifier |
| |
+------------------+
ROM pointer objects are the compiletime resolution of
commands in mobile libraries. A command indentifier
identifier is a pair of 12 bit fields: the first field is a
library ID number, and the second field is the command ID
number within the library.
3.1.4 Binary_Integer_Object
A binary integer object is atomic, has the prologue DOBINT,
and a body which is a 5-nibble number.
+------------------+
| -> DOBINT | Prologue Address
+------------------+
| | Binary
| Number | Body Integer
| | Object
+------------------+
The use of this object type is to represent binary integers
whose precision is equivalent to a memory address.
3.1.5 Real_Number_Object
A real number object is atomic, has the prologue DOREAL, and
a body which is a single-precision floating point number (or
real number, for short).
+-----------------+
| -> DOREAL | Prologue Address
+-----------------+
| |
| Single-precision| Real Number
| Floating Point | Body Object
| Number |
| |
+-----------------+
Page 20
One use of this object type is to represent packed
floating-point numbers (eight bytes) on a Saturn system and,
in this application, the body of the object may consist of
16 BCD nibbles as follows:
(low mem) EEEMMMMMMMMMMMMMMMS
where S is the numeric sign (0 for nonnegative and 9 for
negative), MMMMMMMMMMMM is a 12 digit mantissa with an
implied decimal point between the first and second digits
and the first digit nonzero if the number is nonzero, and
EEE the exponent in tens complement form (-500 < EEE < 500).
3.1.6 Extended_Real_Number_Object
An extended real number object is atomic, has the prologue
DOEREL, and a body which is an extended-precision floating
point number (or extended real, for short).
+-----------------+
| -> DOEREL | Prologue Address
+-----------------+
| | Extended
| Extended- | Real Number
| precision | Object
| Floating Point | Body
| Number |
| |
+-----------------+
One use of this object type is to represent unpacked
floating-point numbers (10.5 bytes) on a Saturn system and,
in this application, the body of the object may consist of
21 BCD nibbles as follows:
(low mem) EEEEEMMMMMMMMMMMMMMMS
where S is the numeric sign (0 for nonnegative, 9 for
negative), MMMMMMMMMMMMMMM is a 15 digit mantissa with an
implied decimal point between the first and second digits
and the first digit nonzero if the number is nonzero, and
EEEEE the exponent in tens complement form (-50000 < EEEEE <
50000).
Page 21
3.1.7 Complex_Number_Object
A complex number object is atomic, has the prologue DOCMP,
and a body which is a pair of real numbers.
+------------------+
| -> DOCMP | Prologue Address
+------------------+
| | Complex
| Real Number | Object
| --------- | Body
| Real Number |
| |
+------------------+
The use of this object type is to represent single-precision
complex numbers, where the real part is interpreted as the
first real number in the pair.
3.1.8 Extended_Complex_Number_Object
An extended complex number object is atomic, has the
prologue DOECMP, and a body which is a pair of extended real
numbers.
+------------------+
| -> DOECMP | Prologue Address
+------------------+
| |
| Extended Real |
| Number | Extended
| ---------- | Body Complex Number
| Extended Real | Object
| Number |
| |
+------------------+
The use of this object type is to represent extended-
precision complex numbers in the same way as for the complex
object.
Page 22
3.1.9 Array_Object
An array object is atomic, has the prologue DOARRY, and a
body which is a collection of the array elements. The body
also includes a length field (indicating the length of the
body), a type indicator (indicating the object type of its
elements), a dimension count field, and length fields for
each dimension.
+------------------+
| -> DOARRY | Prologue Address
+------------------+
| |
| Length Field |
| ------------ |
| Type Indicator |
| ------------ |
| Dimension Count |
| ------------ |
|Dimension 1 Length|
| ------------ |
|Dimension 2 Length|
| ------------ |
| . | Array
| . | Object
| . | Body
| ------------ |
|Dimension N Length|
| ------------ |
| |
| Elements |
| |
+------------------+
The array elements are object bodies of the same object
type. The type indicator is a prologue address (think of
this prologue address as applying to each element of the
array).
Array "OPTION BASE" is always 1. A null array is designated
by any dim limit having the value zero. All elements of an
array object are always present as indicated by the
dimensionality information and are ordered in memory by the
lexicographic order of the array's indices.
3.1.10 Linked_Array_Object
A linked array object is atomic, has the prologue DOLNKARRY,
and a body which is a collection of the array elements. The
body also includes a length field (indicating the length of
the body), a type indicator (indicating the object type of
its elements), a dimension count field, length fields for
each dimension, and a pointer table whose contents are
forward self-relative offsets to the array elements; the
elements of the pointer table are ordered in memory by the
Page 23
lexicographic order of the array's indices.
+------------------+
| -> DOLNKARRY | Prologue Address
+------------------+
| |
| Length Field |
| ------------ |
| Type Indicator |
| ------------ |
| Dimension Count |
| ------------ |
|Dimension 1 Length|
| ------------ |
|Dimension 2 Length|
| ------------ | Linked
| . | Array
| . | Object
| . | Body
| ------------ |
|Dimension N Length|
| ------------ |
| |
| Pointer Table |
| |
| ------------ |
| |
| Elements |
| |
+------------------+
The array elements are object bodies of the same object
type. The type indicator is a prologue address (think of
this prologue address as applying to each element of the
array).
Linked array "OPTION BASE" is always 1. A null linked array
is designated by any dim limit having the value zero. There
is no assumption on the ordering of the elements of a linked
array object, nor on their presence; absence of an element
lying on an allocated dimension is indicated by the value
zero occupying the corresponding pointer table element.
Page 24
3.1.11 Character_String_Object
A character string object is atomic, has the prologue
DOCSTR, and a body which is a character string (a byte
sequence). The body also includes a length field (indicating
the length of the body).
+-------------------+
| -> DOCSTR | Prologue Address
+-------------------+
| | Character
| Length Field | String
| ------------ | Body Object
| Byte Sequence |
| |
+-------------------+
3.1.12 Hex_String_Object
A hex string object is atomic, has the prologue DOHSTR, and
a body which is a nibble sequence. The body also includes a
length field (indicating the length of the body).
+-------------------+
| -> DOHSTR | Prologue Address
+-------------------+
| | Hex
| Length Field | String
| ------------ | Body Object
| Nibble Sequence |
| |
+-------------------+
A typical use for this object type is a buffer or table.
Hex string objects of 16 nibbles or fewer are used to
represent user RPL binary integer objects.
3.1.13 Character_Object
A character object is atomic, has the prologue DOCHAR, and a
body which is a single byte.
+-------------------+
| -> DOCHAR | Prologue Address
+-------------------+
| | Character
| Byte | Body Object
| |
+-------------------+
This object type is used to represent one-byte quantities,
such as ASCII or ROMAN8 characters.
Page 25
3.1.14 Unit_Object
A unit object is composite, has the prologue DOEXT, and
a body which is a sequence consisting of a real number
followed by unit name strings, prefix characters, unit
operators, and real number powers, tail delimited by a
pointer to SEMI.
+-------------------+
| -> DOEXT |
+-------------------+
| Object Sequence |
| |
| ->SEMI |
+-------------------+
3.1.15 Code_Object
A code object is atomic, has the prologue DOCODE, and a body
which is an assembly language slice. The body also includes
a length field (indicating the length of the body). When
executed, the prologue places the system program counter at
the assembly language slice within the body.
+--------------------+
| -> DOCODE | Prologue Address
+--------------------+
| | Code Object
| Length Field |
| ------------ | Body
| Assembly Language |
| Slice |
| |
+--------------------+
The major applications for this object type are assembly
language procedures which can be directly embedded in
composite objects or exist in RAM.
Page 26
3.1.16 Primitive_Code_Object
A primitive code object is a special case of a code object,
used to represent code primitives in built-in libraries.
The prologue of a primitive code object is its body, which
is an assembly language slice; thus, when executed, the body
executes itself.
+------------------+
+----------------- | Prologue Address
| +------------------+
+----->| | Primitive
| Assembly Language| Body Code Object
| Slice |
| |
+------------------+
The primary purpose of this object type is more rapid
execution of code objects in built-in libraries, that is,
these objects are executed without the extra level inherent
in separate prologue execution. However, their structure
implies that (1) they can only exist in built-in libraries
(never in RAM or mobile libraries) since the body must exist
at a fixed address, (2) they cannot be skipped, and (3) they
cannot exist in any situation where traversal may be
required, such as an element of an array or an object within
any composite object.
Note that this object type is an exception to the object
type classification scheme presented at the beginning of
this document. However, an object is a primitive code object
if and only if the prologue address equals the object
address plus 5. In addition, the prologues for this object
type (that is, the object bodies) need not contain logic to
test for direct verses indirect execution since, by
definition, they cannot be executed directly.
3.1.17 Program_Object
A program object (secondary) is composite, has the prologue
DOCOL, and a body which is a sequence of objects and object
pointers, the last of which is an object pointer whose
pointee is the primitive code object SEMI.
+------------------+
| -> DOCOL | Prologue Address
+------------------+
| |
| Object/ | Secondary
| Object Pointer | Object
| Sequence |
| -------- | Body
| -> SEMI |
| |
+------------------+
Page 27
3.1.18 List_Object
A list object is composite, has the prologue DOLIST, and a
body which is a sequence of objects and object pointers, the
last of which is an object pointer whose pointee is the
primitive code object SEMI.
+------------------+
| -> DOLIST | Prologue Address
+------------------+
| |
| Object/ | List
| Object Pointer | Object
| Sequence |
| -------- | Body
| -> SEMI |
| |
+------------------+
3.1.19 Symbolic_Object
A symbolic object is composite, has the prologue DOSYMB, and
a body which is a sequence of objects and object pointers,
the last of which is an object pointer whose pointee is the
primitive code object SEMI.
+------------------+
| -> DOSYMB | Prologue Address
+------------------+
| |
| Object/ | Symbolic
| Object Pointer | Object
| Sequence |
| -------- | Body
| -> SEMI |
| |
+------------------+
This object type is used to represent symbolic objects for
symbolic math applications.
Page 28
3.1.20 Directory_Object
A directory (RAMROMPAIR) object is atomic, has the prologue
DORRP and a body which consists of a Library ID number and a
RAMPART (linked list of variables--object/name pairs.
+----------------+
| -> DORRP | Prologue Address
+----------------+
| | RAMROMPAIR
| ROMPART ID | Object
| -------- | Body
| RAMPART |
+----------------+
3.1.21 Graphics_Object
A graphics object is atomic, has the prologue DOGROB and a
body which consists of the following:
+ A 5 nibble length field for the data which follows.
+ A five nibble quantity that describes the height of the
graphic in pixels.
+ A five nibble quantity that describes the width of the
graphic in pixels.
+ The data.
The actual row dimension in nibbles (W) is always even for
hardware reasons, hence each row of pixel data is padded
with anywhere from 0-7 bits of wasted data.
+----------------+
| -> DOGROB | Prologue Address
+----------------+
| Len(nibs) |
+----------------+
| Height (pixels)| Graphics
+----------------+ Body Object
| Width (pixels) |
+----------------+
| Grob Data |
| ... |
+----------------+
The data nibbles begin at the upper-left corner of the
graphics object and proceed left-to-right, top-to-bottom.
Each row of pixel data is padded as needed to obtain an even
number of nibbles per row. Thus the width in nibbles W is
determined by:
W=CEIL(Width in pixels)/8
Page 29
The bits in each nibble are written in reverse order, so the
leftmost displayed pixel in a nibble is represented by the
least-significant bit of the nibble.
3.2 Terminology and Abbreviations.
In the stack diagrams used throughout the remainder of this
document, the following symbols are used to represent the
various object types:
ob ........... Any object
id ........... Identifier Object
lam .......... Temporary Identifier Object
romptr ....... ROM Pointer Object
__# ............ Binary Integer Object
% ............ Real Object
%% ........... Extended Real Object
C% ........... Complex Object
C%% .......... Extended Complex Object
arry ......... Array Object
lnkarry ...... Linked Array Object
$ ............ Character String Object
hxs .......... Hex String Object
chr .......... Character Object
ext .......... External Object
code ......... Code Object
primcode ..... Primitive Code Object
:: ........... Secondary Object
{} ........... List Object
symb ......... Symbolic Object
comp ......... Any Composite Object (list, secondary, symbolic)
rrp .......... Directory Object
tagged ....... Tagged Object
flag ......... TRUE/FALSE
(TRUE and FALSE above denote the object parts of built-in
ROM-WORDs having these names. The addresses of these objects
(that is, their data stack representations) are interpreted
by RPL control structures as the appropriate truth value.
Both objects are primitive code objects which, when
executed, place themselves on the data stack).
In addition to the above notation, some additional
terminology is useful.
ELEMENT:
An ELEMENT of a composite object is any object or object
pointer in the body of the composite object.
Page 30
CORE:
of a character string: the core of a character string
object is the character data in
the body.
of a hex string: the core of a hex string object is the
nibble sequence in the body.
of a composite: the core of a composite object is the
element sequence in the body not
including the trailing object pointer
to semi.
LENGTH:
of a character string: the length of a character string
object is the number of characters
in the core.
of a hex string: the length of a hex string object is the
number of nibbles in the core.
of a composite: the length of a composite object is the
number of elements in the core.
NULL:
character string: a null character string object is one
whose length is zero.
hex string: a null hex string object is one whose length
is zero.
composite: a null composite object is one whose length
is zero.
INTERNAL:
an internal of a composite object is any object in the
core of the composite object or the pointee of any object
pointer in the core of the composite object.
(A composite object is often loosely referred to as
containing a specific object type, for example "a list of
binary integers"; what is meant is that the core internals
are all of this object type).
Page 31
4. Binary Integers
Internal binary integers have a fixed size of 20 bits, and
are the most often used type for counting, loops, etc.
Binary integers offer advantages of size and speed.
NOTE: User level binary integers are implemented as hex
strings, so a user's object #247d is actually a hex
string, and should not be confused with a binary
integer whose prologue is DOBINT.
4.1 Built-in Binary Integers
The RPLCOMP compiler interprets a decimal number in a source
file as a directive to produce a binary integer object -
using a prologue and a body. Built-in binary integers can
be accessed with just an object pointer. For instance, " 43
" (no quotes) in the source file produces a binary object:
CON(5) =DOBINT
CON(5) 43
The object takes five bytes, but can be replaced by the word
"FORTYTHREE", which is a supported entry point which would
generate the following code:
CON(5) =FORTYTHREE
One pitfall to be aware of in binary integer naming
conventions is the difference between the entries FORTYFIVE
and FOURFIVE. In the former case, the value is decimal 45,
but the latter is decimal 69. Names like 2EXT and IDREAL,
where the values are not obvious, are used in conjunction
with the CK&Dispatch family of argument checking commands.
The names for the CK&Dispatch family are equated to the same
places as other bints. This has been done for readability.
For instance, the word SEVENTEEN, for decimal 17, has the
names 2REAL and REALREAL equated to the same location. A
trailing "d" or "h" on a name such as BINT_122d or BINT80h
indicates the base associated with the value.
Words such as ONEONE, ZEROONE, etc. put more than one binary
integer on the stack. These are indicated by a tiny stack
diagram in parentheses, such as (--> #1 #1 ) for ONEONE.
Page 32
The supported entries for binary integers are listed below
with the hex value in parentheses where needed:
2EXT (#EE) FORTYNINE SYMREAL (#A1)
2GROB (#CC) FORTYONE SYMSYM (#AA)
2LIST (#55) FORTYSEVEN TAGGEDANY (#D0)
2REAL (#11) FORTYSIX TEN
3REAL (#111) FORTYTHREE THIRTEEN
Attn# (#A03) FORTYTWO THIRTY
BINT253 FOUR THIRTYEIGHT
BINT255d FOURFIVE THIRTYFIVE
BINT40h FOURTEEN THIRTYFOUR
BINT80h FOURTHREE THIRTYNINE
BINTC0h FOURTWO THIRTYONE
BINT_115d FOURTY THIRTYSEVEN
BINT_116d IDREAL (#61) THIRTYSIX
BINT_122d INTEGER337 THIRTYTHREE
BINT_130d LISTCMP (#52) THIRTYTWO
BINT_131d LISTLAM (#57) THREE
BINT_65d LISTREAL (#51) TWELVE
BINT_91d MINUSONE(#FFFFF) TWENTY
BINT_96d NINE TWENTYEIGHT
Connecting(#C0A) NINETEEN TWENTYFIVE
EIGHT ONE TWENTYFOUR
EIGHTEEN ONEHUNDRED TWENTYNINE
EIGHTY ONEONE(--> #1 #1) TWENTYONE
EIGHTYONE REALEXT (#1E) TWENTYSEVEN
ELEVEN REALOB (#10) TWENTYSIX
EXT (#E) REALOBOB (#100) TWENTYTHREE
EXTOBOB (#E00) REALREAL (#11) TWENTYTWO
EXTREAL (#E1) REALSYM (#1A) TWO
EXTSYM (#EA) ROMPANY (#F0) XHI
FIFTEEN SEVEN XHI-1 (#82)
FIFTY SEVENTEEN ZERO
FIFTYEIGHT SEVENTY ZEROZERO (--> #0 #0 )
FIFTYFIVE SEVENTYFOUR ZEROZEROONE (--> #0 #0 #1 )
FIFTYFOUR SEVENTYNINE ZEROZEROTWO (--> #0 #0 #2 )
FIFTYNINE SIX ZEROZEROZERO (--> #0 #0 #0 )
FIFTYONE SIXTEEN char (#6F)
FIFTYSEVEN SIXTY id (#6)
FIFTYSIX SIXTYEIGHT idnt (#6)
FIFTYTHREE SIXTYFOUR infreserr (#305)
FIFTYTWO SIXTYONE intrptderr (#a03)
FIVE SIXTYTHREE list (#5)
FIVEFOUR SIXTYTWO ofloerr (#303)
FIVESIX SYMBUNIT (#9E) real (#1)
FIVETHREE SYMEXT (#AE) seco (#8)
FORTY SYMID (#A6) str (#3)
FORTYEIGHT SYMLAM (#A7) sym (#A)
FORTYFIVE SYMOB (#A0) symb (#9)
FORTYFOUR
Page 33
4.2 Binary Integer Manipulation
4.2.1 Arithmetic_Functions
#* ( #2 #1 --> #2*#1 )
#+ ( #2 #1 --> #2+#1 )
#+-1 ( #2 #1 --> #2+#1-1 )
#- ( #2 #1 --> #2-#1 )
#-#2/ ( #2 #1 --> (#2-#1)/2 )
#-+1 ( #2 #1 --> (#2-#1)+1 )
#/ ( #2 #1 --> #remainder #quotient )
#1+ ( # --> #+1 )
#1+' ( # --> #+1 and quotes next runstream object
#1+DUP ( # --> #+1 #+1 )
#1- ( # --> #-1 )
#10* ( # --> #*10 )
#10+ ( # --> #+10 )
#12+ ( # --> #+12 )
#2* ( # --> #*2 )
#2+ ( # --> #+2 )
#2- ( # --> #-2 )
#2/ ( # --> FLOOR(#/2) )
#3+ ( # --> #+3 )
#3- ( # --> #-3 )
#4+ ( # --> #+4 )
#4- ( # --> #-4 )
#5+ ( # --> #+5 )
#5- ( # --> #-5 )
#6* ( # --> #*6 )
#6+ ( # --> #+6 )
#7+ ( # --> #+7 )
#8* ( # --> #*8 )
#8+ ( # --> #+8 )
#9+ ( # --> #+9 )
#MAX ( #2 #1 --> MAX(#2,#1) )
#MIN ( #2 #1 --> MIN(#2,#1) )
2DUP#+ ( #2 #1 --> #2 #1 #1+#2 )
DROP#1- ( # ob --> #-1 )
DUP#1+ ( # --> # #+1 )
DUP#1- ( # --> # #-1 )
DUP3PICK#+ ( #2 #1 --> #2 #1 #1+#2 )
OVER#+ ( #2 #1 --> #2 #1+#2 )
OVER#- ( #2 #1 --> #2 #1-#2 )
ROT#+ ( #2 ob #1 --> ob #1+#2 )
ROT#+SWAP ( #2 ob #1 --> #1+#2 ob )
ROT#- ( #2 ob #1 --> ob #1-#2 )
ROT#1+ ( # ob ob' --> ob ob' #+1 )
ROT+SWAP ( #2 ob #1 --> #1+#2 ob )
SWAP#- ( #2 #1 --> #1-#2 )
SWAP#1+ ( # ob --> ob #+1 )
SWAP#1+SWAP ( # ob --> #+1 ob )
SWAP#1- ( # ob --> ob #-1 )
SWAP#1-SWAP ( # ob --> #-1 ob )
SWAPOVER#- ( #2 #1 --> #1 #2-#1 )
Page 34
4.2.2 Conversion_Functions
COERCE ( % --> # ) If %<0 then # is 0
If %>FFFFF then #=FFFFF
COERCE2 ( %2 %1 --> #2 #1 ) See COERCE
COERCEDUP ( % --> # # ) See COERCE COERCESWAP (
ob % --> # ob ) UNCOERCE ( # --> % )
UNCOERCE%% ( # --> %% ) UNCOERCE2 ( #2 #1 --> %2
%1 )
Page 35
5. Character Constants
The following words are useful for converting between
character objects and other object types:
CHR># ( chr --> # )
#>CHR ( # --> chr )
CHR>$ ( chr --> $ )
The following character constants and strings are supported:
CHR_# CHR_* CHR_+ CHR_, CHR_- CHR_. CHR_/ CHR_0 CHR_1 CHR_2
CHR_3 CHR_4 CHR_5 CHR_6 CHR_7 CHR_8 CHR_9 CHR_: CHR_; CHR_<
CHR_= CHR_> CHR_A CHR_B CHR_C CHR_D CHR_E CHR_F CHR_G CHR_H
CHR_I CHR_J CHR_K CHR_L CHR_M CHR_N CHR_O CHR_P CHR_Q CHR_R
CHR_S CHR_T CHR_U CHR_V CHR_W CHR_X CHR_Y CHR_Z CHR_a CHR_b
CHR_c CHR_d CHR_e CHR_f CHR_g CHR_h CHR_i CHR_j CHR_k CHR_l
CHR_m CHR_n CHR_o CHR_p CHR_q CHR_r CHR_s CHR_t CHR_u CHR_v
CHR_w CHR_x CHR_y CHR_z
CHR_00 (hex 0) CHR_... CHR_DblQuote CHR_-> CHR_<<
CHR_>> CHR_Angle CHR_Deriv CHR_Integral CHR_LeftPar
CHR_Newline CHR_Pi CHR_RightPar CHR_Sigma CHR_Space
CHR_UndScore CHR_[ CHR_] CHR_{ CHR_} CHR_<= CHR_>=
CHR_<>
$_R<< ( $ "R\80\80" "R<angle><angle>" )
$_R<Z ( $ "R\80Z" "R<angle>Z" )
$_XYZ ( $ "XYZ" )
$_<<>> ( $ "ABBB" )
$_{} ( $ "{}" )
$_[] ( $ "[]" )
$_'' ( $ "''" )
$_:: ( $ "::" )
$_LRParens ( $ "()" )
$_2DQ ( $ """""" )
$_ECHO ( $ "ECHO" )
$_EXIT ( $ "EXIT" )
$_Undefined ( $ "Undefined" )
$_RAD ( $ "RAD" )
$_GRAD ( $ "GRAD" )
NEWLINE$ ( $ "\0a" )
SPACE$ ( $ " " )
Page 36
6. Hex & Character Strings
6.1 Character Strings
The following words are avaliable for character string
manipulation:
&$ ( $1 $2 --> $3 )
Appends $2 to $1
!append$ ( $1 $2 --> $3 )
Same as &$, except that it will attempt the concatenation
"in place," if there is not enough memory for the new
string, and the target is in tempob.
$>ID ( $name --> Id )
Converts string object to name object
&$SWAP ( ob $1 $2 --> $3 ob )
Appends $2 to $1, then swaps result with ob )
1-#1-SUB$ ( $ # --> $' )
Where $' = chars 1 thru #-1 of $
>H$ ( $ chr --> $' )
Prepends chr to $
>T$ ( $ chr --> $' )
Appends chr to $
AND$ ( $1 $2 --> $1 AND $2 )
Bitwise logical AND of two strings
APPEND_SPACE ( $ --> $' )
Appends space to $
Blank$ ( # --> $ )
Creates a string of # spaces
CAR$ ( $ --> chr | $ )
Returns 1st chr of $ or NULL$ if $ is null
CDR$ ( $ --> $' )
$' is $ minus first character. Returns NULL$ if $ is null
COERCE$22 ( $ --> $' )
If $ longer than 22 chars., truncates to 21 chars &
appends "..."
DECOMP$ ( ob --> $ )
Decompiles object for stack display
DO>STR ( ob --> $ )
Internal version of ->STR
DROPNULL$ ( ob --> NULL$ )
Drops object, returns zero-length string
DUP$>ID ( $name --> $name Id )
Dups, converts string object to name object
DUPLEN$ ( $ --> $ #length )
Returns $ and its length
DUPNULL$? ( $ --> $ flag )
Returns TRUE if $ is zero-length
EDITDECOMP$ ( ob --> $ )
Decompile object for editing
JstGETTHEMESG ( # --> $ )
Fetches message from message table
ID>$ ( ID --> $name )
Converts name object to a string
LAST$ ( $ # --> $' )
Returns last # chrs of $
Page 37
LEN$ ( $ --> #length )
Returns length of $
NEWLINE$&$ ( $ --> $' )
Appends "\0a" to $
NULL$ ( --> $ )
Returns empty string
NULL$? ( $ --> flag )
Returns TRUE if $ is zero-length
NULL$SWAP ( ob --> $ ob )
Swaps empty string into level 2
NULL$TEMP ( --> $ )
Creates empty string in TEMPOB
OR$ ( $1 $2 --> $3 )
Bitwise logical OR of two strings
OVERLEN$ ( $ ob --> $ ob #length )
Returns length of $ in level 2
POS$ ( $search $find #start --> #pos )
Returns #pos (#0 if not found) of $find
within $search starting at head of $search
POS$REV ( $search $find #start --> #pos )
Returns #pos (#0 if not found) of $find
within $search starting at tail of $search
PromptIdUtil ( id ob -> $ )
Returns string in the form "id: ob"
SEP$NL ( $ --> $2 $1 )
Separate $ at newline character
SUB$ ( $ #start #end --> $' )
Returns substring of $
SUB$1# ( $ #pos --> # )
Returns bint with value of character
in $ at position #pos
SUB$SWAP ( ob $ #start #end --> $' ob )
Returns substring of $ and swaps with ob
SWAP&$ ( $1 $2 --> "$2$1" )
Appends $1 to $2
TIMESTR ( %date %time --> "WED 03/30/90 11:30:15A" )
Returns string time and date
(like user word TSTR)
XOR$ ( $1 $2 --> $3 )
Bitwise logical XOR of two strings
a%>$ ( % --> $ )
Converts % to $ using current display mode
a%>$, ( % --> $ )
Converts % to $ using current display mode
Same as a%>$, but with no commas
palparse ( $ --> ob TRUE )
( $ --> $ #pos $' FALSE )
Parse a string into an object and TRUE, or
returns position of error and FALSE
Page 38
6.2 Hex Strings
#>% ( hxs --> % )
Converts hxs to real
%># ( % --> hxs )
Converts real to hxs
&HXS ( hxs1 hxs2 --> hxs3 )
Appends hxs2 to hxs1
2HXSLIST? ( { hxs1 hxs2 } --> #1 #2 )
Converts list of two hxs into two bints
Generates Bad Argument Value error for
invalid input
HXS#HXS ( hxs1 hxs2 --> %flag )
Returns %1 if hxs1 <> hxs2, otherwise %0
HXS># ( hxs --> # )
Converts lower 20 bits of hxs into a bint
HXS>$ ( hxs --> $ )
Does hxs>$, then appends base character
HXS>% ( hxs --> % )
Converts hex string to real number
HXS<HXS ( hxs1 hxs2 --> %flag )
Returns %1 if hxs1<hxs2, otherwise %0
HXS>HXS ( hxs1 hxs2 --> %flag )
Returns %1 if hxs1>hxs2, otherwise %0
HXS>=HXS ( hxs1 hxs2 --> %flag )
Returns %1 if hxs1>=hxs2, otherwise %0
HXS<=HXS ( hxs1 hxs2 --> %flag )
Returns %1 if hxs1<=hxs2, otherwise %0
LENHXS ( hxs --> #length )
Returns # of nibbles in hxs
NULLHXS ( --> hxs )
Returns zero-length hex string
SUBHXS ( hxs #m #n --> hxs' )
Returns substring
User RPL binary integers are actually hex strings. The
following words assume 64-bit or shorter hex strings, and
return results according to the current wordsize:
bit/ ( hxs1 hxs2 --> hxs3 )
Divides hxs1 by hxs2 bit%#/ ( % hxs --> hxs' )
Divides % by hxs, returns hxs
bit#%/ ( hxs % --> hxs' ) Divides
hxs by %, returns hxs bit* ( hxs1 hxs2 --> hxs3 )
Multiplies hxs1 by hxs2 bit%#* (
% hxs --> hxs' ) Multiplies % by hxs,
returns hxs bit#%* ( hxs % --> hxs' )
Multiplies hxs by %, returns hxs
bit+ ( hxs1 hxs2 --> hxs3 )
Adds hxs1 to hxs2 bit%#+ ( % hxs --> hxs' )
Adds % to hxs, returns hxs
bit#%+ ( hxs % --> hxs' ) Adds
hxs to %, returns hxs bit- ( hxs1 hxs2 --> hxs3 )
Subtracts hxs2 from hxs1 bit%#- (
% hxs --> hxs' ) Suptracts % from hxs,
returns hxs bit#%- ( hxs % --> hxs' )
Suptracts hxs from %, returns hxs
Page 39
bitAND ( hxs1 hxs2 --> hxs3 )
Bitwise logical AND bitASR ( hxs --> hxs' )
Arithmetic shift right one bit
bitOR ( hxs1 hxs2 --> hxs3 )
Bitwise logical OR bitNOT ( hxs1 hxs2 --> hxs3 )
Bitwise logical NOT bitRL ( hxs
--> hxs' ) Circular left shift by 1 bit
bitRLB ( hxs --> hxs' ) Circular
left shift by 1 byte bitRR ( hxs --> hxs' )
Circular right shift by 1 bit
bitRRB ( hxs --> hxs' ) Circular
right shift by 1 byte bitSL ( hxs --> hxs' )
Shift left by 1 bit bitSLB ( hxs
--> hxs' ) Shift left by 1 byte
bitSR ( hxs --> hxs' ) Shift
right by 1 bit bitSRB ( hxs --> hxs' )
Shift right by 1 byte bitXOR (
hxs1 hxs2 --> hxs3 ) Bitwise logical XOR
Wordsize control:
WORDSIZE ( --> # ) Returns user
binary integer wordsize dostws ( # --> )
Stores binary wordsize hxs>$ (
hxs --> $ ) Converts hex string to chr
string using the current display mode and
wordsize
Page 40
7. Real Numbers
Real numbers are written with %, and extended real numbers
are written with %%.
7.1 Built-in Reals
The following real and extended real numbers are built in:
%%.1 %%4 %-8 %11 %21 %5
%%.4 %%5 %-9 %12 %22 %6
%%.5 %%60 %-MAXREAL %13 %23 %7
%%0 %%7 %-MINREAL %14 %24 %8
%%1 %-2 %.1 %15 %25 %MAXREAL
%%10 %-3 %.5 %16 %26 %MINREAL
%%12 %-4 %0 %17 %27 %PI
%%2 %-5 %1 %180 %3 %e
%%2PI %-6 %10 %2 %360 %-1
%%3 %-7 %100 %20 %4
7.2 Real Number Functions
In the stack diagrams below, %1 and %2 refer to two
different real numbers, NOT the real numbers one and two.
%%* ( %%1 %%2 --> %%3 )
Multiplies two extended reals
%%*ROT ( ob1 ob2 %%1 %%2 --> ob2 %%3 ob1 )
Multiplies two extended reals,
then does a ROT
%%*SWAP ( ob %%1 %%2 --> %%3 ob )
Multiplies two extended reals,
then does a SWAP
%%*UNROT ( ob1 ob2 %%1 %%2 --> %%3 ob1 ob2 )
Multiplies two extended reals,
then does an UNROT
%%+ ( %%1 %%2 --> %%3 )
Adds two extended reals
%%- ( %%1 %%2 --> %%3 )
Subtraction
%%ABS ( %% --> %%' )
Absolute value
%%ACOSRAD ( %% --> %%' )
Arc-cosine using radians
%%ANGLE ( %%x %%y --> %%angle )
Angle using current angle mode from %%x %%y
%%ANGLEDEG ( %%x %%y --> %%angle )
Angle using degrees from %%x %%y
Page 41
%%ANGLERAD ( %%x %%y --> %%angle )
Angle using radians from %%x %%y
%%ASINRAD ( %% --> %%' )
Arc-sine using radians
%%CHS ( %% --> %%' )
Change sign
%%COS ( %% --> %%' )
Cosine
%%COSDEG ( %% --> %%' )
Cosine using degrees
%%COSH ( %% --> %%' )
Hyperbolic cosine
%%COSRAD ( %% --> %%' )
Cosine using radians
%%EXP ( %% --> %%' )
e^x
%%FLOOR ( %% --> %%' )
Greatest integer <= x
%%H>HMS ( %% --> %%' )
Decimal hours to hh.mmss
%%INT ( %% --> %%' )
Integer part
%%LN ( %% --> %%' )
ln(x)
%%LNP1 ( %% --> %%' )
ln(x+1)
%%MAX ( %%1 %%2 --> %%3 )
Returns greater of two %%s
%%P>R ( %%radius %%angle --> %%x %%y )
Polar to rectangular conversion
%%R>P ( %%x %%y --> %%radius %%angle )
Rectangular to polar conversion
%%SIN ( %% --> %%' )
Sine
%%SINDEG ( %% --> %%' )
Sine using degrees
%%SINH ( %% --> %%' )
Hyperbolic sine
%%SQRT ( %% --> %%' )
Square root
%%TANRAD ( %% --> %%' )
Tangent using radians
%%^ ( %%1 %%2 --> %%3 )
Exponential
%+ ( %1 %2 --> %3 )
Addition
%+SWAP ( ob %1 %2 --> %3 ob )
Addition, then SWAP
%- ( %1 %2 --> %3 )
Subtraction
%1+ ( % --> %+1 )
Adds one
%1- ( % --> %-1 )
Subtracts one
Page 42
%># ( % --> hxs )
Converts real to binary integer
%>%% ( % --> %% )
Converts real to extended real
%>%%- ( %1 %2 --> %%3 )
Converts 2 % to %%, then subtracts
%>%%1 ( %x --> %% )
Converts % to %%, then does 1/x
%>%%ANGLE ( %x %y --> %%angle )
Angle in current angle mode
%>%%SQRT ( % --> %% )
Converts % to %%, then sqrt(x)
%>%%SWAP ( ob % --> %% ob )
Converts % to %%, then SWAP
%>C% ( %real %imag --> C% )
Real to complex conversion
%>HMS ( % --> %hh.mmss )
Decimal hours to hh.mmss
%ABS ( % --> %' )
Absolute value
%ABSCOERCE ( % --> # )
Absolute value, convert to bint
%ACOS ( % --> %' )
Arc cosine
%ACOSH ( % --> %' )
Hyperbolic arc cosine
%ALOG ( % --> %' )
10^x
%ANGLE ( %x %y --> %angle )
Angle using current angle mode from %x %y
%ASIN ( % --> %' )
Arc sine
%ASINH ( % --> %' )
Hyperbolic arc sine
%ATAN ( % --> %' )
Arc tangent
%ATANH ( % --> %' )
Hyperbolic arc tangent
%CEIL ( % --> %' )
Next greatest integer
%CH ( %1 %2 --> %3 )
Percent change
%CHS ( % --> %' )
Change sign
%COMB ( %m %n -> %COMB(m,n) )
Combinations of m items taken n at a time
%COS ( % --> %' )
Cosine
%COSH ( % --> %' )
Hyperbolic cosine
%D>R ( % --> %' )
Degrees to radians
%EXP ( % --> %' )
e^x
%EXPM1 ( $ --> %' )
e^x-1
Page 43
%EXPONENT ( % --> %' )
Returns exponent
%FACT ( % --> %! )
Factorial
%FLOOR ( % --> %' )
Greatest integer <= x
%FP ( % --> %' )
Fractional part
%HMS+ ( %1 %2 --> %3 )
HH.MMSS addition
%HMS- ( %1 %2 --> %3 )
HH.MMSS subtraction
%HMS> ( % --> %' )
Convert hh.mmss to decimal hours
%IP ( % --> %' )
Integer part
%IP># ( % --> # )
IP(ABS(x) converted to binary integer
%LN ( % --> %' )
ln(x)
%LNP1 ( % --> %' )
ln(x+1)
%LOG ( % --> %' )
Common log
%MANTISSA ( % --> %' )
Returns mantissa
%MAX ( %1 %2 --> % )
Returns larger of two reals
%MAXorder ( %1 %2 --> %larger %smaller )
Orders two numbers
%MIN ( %1 %2 --> % )
Returns smaller of two reals
%MOD ( %1 %2 --> %3 )
Returns %1 MOD %2
%NFACT ( % --> %' )
Factorial
%NROOT ( %1 %2 --> %3 )
Nth root
%OF ( %1 %2 --> %3 )
Returns percantage of %1 that is %2
%PERM ( %m %n --> %PERM(%m,%n) )
Returns permutations of %m items
taken %n at a time
%POL>%REC ( %x %y --> %radius %angle )
Rectangular to polar conversion
%R>D ( %radians --> %degrees )
Radians to degrees
%RAN ( --> %random )
Random number
%RANDOMIZE ( %seed --> )
Updates random number seed, uses the
system clock if %=0
%REC>%POL ( %radius %angle --> %x %y )
Polar to rectangular conversion
%SGN ( % --> %' )
Sign: -1, 0 or 1 returned depending
on the sign of the argument
%SIN ( % --> %' )
Page 44
Sine
%SINH ( % --> %' )
Hyperbolic sine
%SPH>%REC ( %r %th %ph --> %x %y %z )
Spherical to rectangular conversion
%SQRT ( % --> %' )
Square root
%T ( %1 %2 --> %3 )
Percent total
%TAN ( % --> %' )
Tangent
%TANH ( % --> %' )
Hyperbolic tangent
%^ ( %1 %2 --> %3 )
Exponential
2%%>% ( %%1 %%2 --> %1 %2 )
Extended real to real conversion
2%>%% ( %1 %2 --> %%1 %%2 )
Real to extended real conversion
C%>% ( C% --> %real %imag )
Complex to real conversion
DDAYS ( %date1 %date2 --> %diff )
Days between dates in DMY format
DORANDOMIZE ( % --> )
Updates random number seed
RNDXY ( %number %places --> %number' )
Rounds %number to %places
TRCXY ( %number %places --> %number' )
Truncates %number to %places
SWAP%>C% ( %imag %real --> C% )
Real to complex conversion
Page 45
8. Complex Numbers
Complex numbers are represented by C%, extended complex
numbers by C%%.
8.1 Built-in Complex Numbers
C%0 (0,0)
C%1 (1,0)
C%-1 (-1,0)
C%%1 (%%1,%%0)
8.2 Conversion Words
%>C% ( %real %imag --> C% )
%%>C%% ( %%real %%imag --> C%% )
%%>C% ( %%real %%imag --> C% )
C%>% ( C% --> %real %imag )
C%%>%% ( C%% --> %%real %%imag )
C%%>C% ( C%% --> C% )
C%>%% ( C% --> %%real %%imag )
C%>%%SWAP ( C% --> %%imag %%real )
C>Im% ( C% --> %imag )
C>Re% ( C% --> %real )
8.3 Complex Functions
C%1/ ( C% --> C%' )
Inverse
C%ABS ( C% --> % )
Returns SQRT(x^2+y^2) from (x,y)
C%ACOS ( C% --> C%' )
Arc cosine
C%ALOG ( C% --> C%' )
Common antilog
C%ARG ( C% --> %)
Returns ANGLE(x,y) from (x,y)
C%ASIN ( C% --> C%' )
Arc sine
C%ATAN ( C% --> C%' )
Arc tangent
C%C^C ( C%1 C%2 --> C%3 )
Power
C%CHS ( C% --> C%' )
Change sign
C%%CHS ( C%% --> C%%' )
Change sign
C%CONJ ( C% --> C%' )
Conjugate
C%%CONJ ( C%% --> C%%' )
Conjugate
Page 46
C%COS ( C% --> C%' )
Cosine
C%COSH ( C% --> C%' )
Hyperbolic cosine
C%EXP ( C% --> C%' )
e^z
C%LN ( C% --> C%' )
Natural logarithm
C%LOG ( C% --> C%' )
Common logarithm
C%SGN ( C% --> C%' )
Returns (x/SQRT(x^2+y^2),y/SQRT(x^2+y^2)
C%SIN ( C% --> C%' )
Sine
C%SINH ( C% --> C%' )
Hyperbolic sine
C%SQRT ( C% --> C%' )
Square root
C%TAN ( C% --> C%' )
Tangent
C%TANH ( C% --> C%' )
Hyperbolic tangent
Page 47
9. Arrays
The notation [array] represents a real or complex array.
[arry%] and [arryC%] represent real and complex arrays,
respectively. {dims} means a list of array dimensions,
which may be either { #cols } or { #rows #cols }.
Unless otherwise indicated, the following words do NOT check
for out-of-range conditions (i.e. elements specified that
are not within the range of the current array).
ARSIZE ( [array] --> #elements )
( [array] --> {dims} )
GETATELN ( # [array] --> ob TRUE )
( # [array] --> FALSE ) (no such element)
MAKEARRY ( {dims} ob --> [array] )
Creates an unlinked array having the same
element type as ob. All elements are
initialized to ob.
MATCON ( [arry%] % --> [arry%]' )
( [arryC%] C% --> [arryC%]' )
Sets all elements in array to % or C%.
MATREDIM ( [array] {dims} --> [array]' )
MATTRN ( [array] --> [array]' )
MDIMS ( [1-D array] --> #m FALSE )
( [2-D array] --> #m #n TRUE )
MDIMSDROP ( [2-D array] --> #m #n )
Don't use MDIMSDROP on a vector!
OVERARSIZE ( [array] ob --> [array] ob #elements )
PULLREALEL ( [arry%] # --> [arry%] % )
PULLCMPEL ( [arryC%] # --> [arryC%] C% )
PUTEL ( [arry%] % # --> [arry%]' )
( [arryC%] C% # --> [arryC%] )
PUTREALEL ( [arry%] % # --> [arry%]' )
PUTCMPEL ( [arryC%] C% # --> [arryC%]' )
Page 48
10. Composite Objects
The words described in this chapter are used for
manipulating composite objects - mainly lists and
secondaries. In the notation below, the term "comp" refers
to either any composite object. The term "#n" refers to the
number of objects in a composite object, and the term "#i"
refers to the index of an object within a composite. The
term "flag" refers to TRUE or FALSE.
&COMP ( comp comp' --> comp'' ) comp is concatenated to comp'
2Ob>Seco ( ob1 ob2 --> :: ob1 ob2 ; )
::N ( obn ... ob1 #n --> :: obn ... ob1 ; )
::NEVAL ( obn ... ob1 #n --> ? )
Does ::N, then evaluates secondary
>TCOMP ( comp ob --> comp' ) ob is added to the tail of comp
CARCOMP ( comp --> ob )
( comp --> comp )
Returns first object in the core of the
composite. Returns an null comp if the
supplied composite is null.
CDRCOMP ( comp --> comp' )
( comp --> comp )
Returns the core of the composite minus the
first object. Returns null comp if if the
supplied composite is null.
DUPINCOMP ( comp --> comp obn ... ob1 #n )
DUPLENCOMP ( comp --> comp #n )
DUPNULLCOMP? ( comp --> comp flag ) TRUE if comp is null.
DUPNULL{}? ( {list} --> {list} flag ) TRUE if {list} is null.
EQUALPOSCOMP ( comp ob --> #pos | #0 )
Returns the index of the first object in comp
matching (EQUAL) ob (see NTHOF also)
Embedded? ( ob1 ob2 --> flag )
Returns TRUE if ob2 is embedded in, or the
same as, ob1; otherwise returns FALSE.
INCOMPDROP ( comp --> obn ... ob1 )
INNERCOMP ( comp --> obn ... ob1 #n )
INNERDUP ( comp --> obn ... ob1 #n #n )
LENCOMP ( comp --> #n )
NEXTCOMPOB ( comp #offset --> comp #offset' ob TRUE )
( comp #offset --> comp FALSE )
#offset is the nibble offset from the start
of the list to the Nth object in the list.
Returns a new #offset and the next object if
the next object is not SEMI, otherwise
returns the list and FALSE. Use #5 at the
start of the list.
NTHCOMDDUP ( comp #i --> ob ob )
NTHCOMPDROP ( comp #i --> ob )
NTHELCOMP ( comp #i --> ob TRUE )
( comp #i --> FALSE )
Returns FALSE if #i is out of range
NTHOF ( ob comp --> #i | #0 ) Same as SWAP EQUALPOSCOMP.
NULL:: ( --> :: ; ) (Returns null secondary)
NULL{} ( --> { } ) (Returns null list)
Page 49
ONE{}N ( ob --> { ob } )
Ob>Seco ( ob --> :: ob ; )
POSCOMP ( comp ob pred --> #i | #0 )
If the specified object "matches" an element
of the specified composite, where "match" is
defined as the specified predicate returning
TRUE when applied to an element of the comp
and the object, then POSCOMP returns the left-
to- right index of the element within the
composite, or zero. For instance, to find the
first real less than 5 in a list of reals:
:: {list} 5 ' %< POSCOMP ;
PUTLIST ( ob #i {list} --> {list}' ) (Assumes 0<#i<=#n)
SUBCOMP ( comp #m #n --> comp' ) (Returns subcomposite)
IF #m > #n THEN comp' is null
IF #m=0 THEN #m is set to 1
IF #n=0 THEN #n is set to 1
IF #m > LEN(comp) THEN comp' is null
IF #n > LEN(comp) THEN #n is set to LEN(comp)
SWAPINCOMP ( comp obj --> obj obn ... ob1 #n )
THREE{}N ( ob1 ob2 ob3 --> { ob1 ob2 ob3 } )
TWO{}N ( ob1 ob2 --> { ob1 ob2 } )
{}N ( obn ... ob1 #n --> {list} )
apndvarlst ( {list} ob --> {list}' )
Adds ob to the list if ob is not found within
the list
matchob? ( ob comp --> ob TRUE )
( ob comp --> FALSE )
Determines if ob is equal (EQUAL) to any element of comp
Page 50
11. Tagged Objects
The following words are available for manipulating tagged
objects. Remember that an object can have multiple tags.
%>TAG ( ob % --> tagged )
Tags ob with %
>TAG ( ob $ --> tagged )
Tags ob with $
ID>TAG ( ob id/lam --> tagged )
Tags ob with id
STRIPTAGS ( tagged --> ob )
Removes all tags
STRIPTAGSl2 ( tagged ob' --> ob ob' )
Strips tags from level 2 object
TAGOBS ( ob $ --> tagged )
( ob1 ... obn { $1 ... $n }
--> tagged1 ... taggedn )
Tags one object, or several objects
if a list of tags is in level 1
USER$>TAG ( ob $ --> tagged )
Tags ob with $ (up to 255 chrs valid)
Page 51
12. Unit Objects
When unit objects are compared for dimensional consistency,
a hex string, called a "quantity string", may be extracted
using the word U>NCQ. This quantity string contains
information about which units are contained, and can be
directly compared with another quantity string. If the
quantity strings match, the two unit objects can be said to
be dimensionally consistent. U>NCQ also returns extended
real numbers consisting of the number and a conversion
factor to base units.
U>NCQ ( unit --> n%% cf%% qhxs )
Returns number, conversion factor,
and hex quantity string
UM=? ( unit1 unit2 --> %flag )
Returns %1 if two unit obs are equal
UM#? ( unit1 unit2 --> %flag )
Returns %1 if unit1 <> unit2
UM<? ( unit1 unit2 --> %flag )
Returns %1 if unit1 < unit2
UM>? ( unit1 unit2 --> %flag )
Returns %1 if unit1 > unit2
UM<=? ( unit1 unit2 --> %flag )
Returns %1 if unit1 <= unit2
UM>=? ( unit1 unit2 --> %flag )
Returns %1 if unit1 >= unit2
UM>U ( % unit --> unit' )
Replaces the number part of a unit object
UM% ( unit %percentage --> unit' )
Returns a percentage of a unit object
UM%CH ( unit1 unit2 --> % )
Returns percent difference
UM%T ( unit1 unit2 --> % )
Returns percentage fraction
UM+ ( unit1 unit2 --> unit3 )
Addition
UM- ( unit1 unit2 --> unit3 )
Subtraction
UM* ( unit1 unit2 --> unit3 )
Multiply
UM/ ( unit1 unit2 --> unit3 )
Divide
UM^ ( unit1 unit2 --> unit3 )
Power
UM1/ ( unit --> unit' )
Inverse
UMABS ( unit --> unit' )
Absolute value
UMCHS ( unit --> unit' )
Change sign
UMCONV ( unit1 unit2 --> unit1' )
Converts unit1 to units of unit2
UMCOS ( unit --> unit' )
Cosine
UMMAX ( unit1 unit2 --> unit? )
Page 52
Returns larger of unit1 and unit2
UMMIN ( unit1 unit2 --> unit? )
Returns smaller of unit1 and unit2
UMSI ( unit --> unit' )
Convert to SI base units
UMSIN ( unit --> unit' )
Sine
UMSQ ( unit --> unit' )
Square
UMSQRT ( unit --> unit' )
Square root
UMTAN ( unit --> unit' )
Tangent
UMU> ( unit --> % unit' )
Returns number and normalized unit parts
of a unit object
UMXROOT ( unit1 unit2 --> unit3 )
unit1^1/unit2
UNIT>$ ( unit --> $ )
Decompiles a unit object with tics
Page 53
13. Temporary Variables and Temporary Environments
One of the features implemented in RPL is the capability of
creating temporary variables (aka "local variables", "lambda
variables") whose names are given by the programmer, and
which can be destroyed easily when they are no longer
needed. These temporary variables serve a number of
important purposes. First of all, they can be used to
eliminate stack manipulations within a program, which makes
the task of keeping track of the stack much easier, and
makes debugging easier. In addition, they are essential for
the implementation of programs which take an indefinite
number of parameters and want to save one or more of those
parameters.
Temporary variables are referenced by temporary identifier
objects ("local names"), and the binding between a temporary
identifier object and its value is supported by structures
in memory called temporary environments. (This is the RPL
analogue of LISP "lambda binding").
Temporary environments are stacked in chronological order.
This allows the programmer the opportunity to create his own
"private" temporary variables, without the possibility of
interfering with those created by others. When a temporary
identifier object is executed, a search is made through the
stack of temporary environments, starting in the most
recently created and working back through previous
environments if necessary. When a match is made between the
temporary identifier object being executed and a temporary
identifier object in one of the temporary environments, the
object bound to that identifier is pushed onto the data
stack. Executing an unbound temporary identifier object is
an error condition.
The processes of creating a temporary environment and
assigning initial values to its temporary variables are
accomplished simultaneously with the provided object BIND.
BIND expects a list of temporary identifier objects on the
top of the data stack and at least as many objects
(excluding the list itself) on the stack as there are
temporary identifier objects in the list. BIND will then
create a temporary environment and bind each temporary
identifier object in the list with an object on the stack,
removing that object from the stack.
Subsequent execution of any of the temporary identifier
objects in the list will return the object bound to it. The
value bound to a temporary identifier object can be changed
using STO in exactly the same manner as a value "bound" to
an identifier object (global name).
The dissolution of a temporary environment is accomplished
with the provided object ABND (short for "abanbon"). ABND
removes the top-most temporary environment from the stack of
temporary environments. Individual temporary variables
cannot be removed from a temporary environment; the
temporary environment as a whole must be abandoned.
Page 54
Note that the RPL compiler does not check to see if there is
an ABND to match each BIND. You can include the two within
a single program, or put them in separate programs as you
like with no restrictions other than the requirements of
good structured programming practice. This also means that
you must remember to include the ABND at some point,
otherwise you may leave unnecessary environments around
after a program has completed execution. (In user RPL, you
do not have such freedom. The structure word -> has BIND
built into it, and the command line parser demands that
there be a matching >> or ' that includes ABND.)
13.1 Structure of the Temporary Environment Area
The structure of the temporary environment area is shown
below.
--------------------------
| Link Field |-----+ (The first
---------------------------------| | temporary
| First Temporary Environment | | environment
---------------------------------- | is that most
| recently
-------------------------- | created)
+------------| Link Field |<----+
| ---------------------------------|
| | Second Temporary Environment |
| ----------------------------------
. .
. .
. .
| -------------------------
+-----------> | Link Field |-----+
---------------------------------| |
| Last Temporary Environment | |
---------------------------------- |
|
------------------------- |
| 0 |<----+
-------------------------
(high memory)
Page 55
Each temporary environment consists of a protection word (a
binary integer object body) which is used in error handling,
followed by a sequence of one or more pairs of object
pointers. The first object pointer in each pair is the
address of a temporary identifier object and the second
object pointer in each pair is the address of the object
bound to that temporary identifier object. All of the object
pointers in a temporary environment are updatable. The
structure of each temporary environment within the temporary
environment area is shown below.
----------------------------------------------------- (lower addresses)
| Protection Word |
|---------------------------------------------------|
| -> Temporary Identifier Object 1 |
|---------------------------------------------------|
| -> Object Bound to Temporary Identifier Object 1 |
|---------------------------------------------------|
| -> Temporary Identifier Object 2 |
|---------------------------------------------------|
| -> Object Bound to Temporary Identifier Object 2 |
|---------------------------------------------------|
| . |
| . |
| . |
|---------------------------------------------------|
| -> Temporary Identifier Object N |
|---------------------------------------------------|
| -> Object Bound to Temporary Identifier Object N |
----------------------------------------------------- (higher addresses)
Page 56
13.2 Named vs. Unnamed Temporary Variables
Temporary variables are normally named by the corresponding
temporary identifier in the list used by BIND. The names in
the list are used in the same order as the bound objects
appear on the stack--the last identifier in the list
corresponds to the object in level 1, the next-to-last
identifier corresponds to the object in level 2, and so on.
In the following example, the binary integer ONE is bound
into Var1, and TWO is bound into Var2:
ONE TWO
{
' LAM Var1
' LAM Var2
}
BIND ( Binds ONE into temporary variable Var1, and
TWO into variable Var2 )
...
LAM Var1 ( Recalls ONE from Var1 )
...
LAM Var2 ( Recalls TWO from Var2 )
...
' LAM Var1 STO ( Stores new object in Var1 )
...
ABND ( Abandons temp env. )
Temporary identifiers may contain any text characters,
except that you should not start the names with ' or # as
such names are reserved for the built-in ROM programs. For
similar reasons, it is recommended that you use names that
can not conflict with user-generated names; an easy way to
insure this is to include an "illegal" character such as one
of the object delimiters in your names.
Page 57
If there is NO CHANCE that another temporary environment
will be created above the environment you are about to
create, null names may be used to save memory. There are a
number of utility words that allow you to access local
variables in the topmost environment by position number,
which is faster than the ordinary name resolution. For
example, the example above would look like this:
::
ONE TWO
{ NULLLAM NULLLAM }
BIND ( Binds ONE and TWO into nullnamed temporary
variables )
...
2GETLAM ( Recalls ONE from first variable )
...
1GETLAM ( Recalls TWO from last variable )
...
2PUTLAM ( Stores new object in first variable )
...
ABND ( Abandons temp environment. )
;
The numbering starts with the last temporary variable (i.e.
in the same order as the stack level number).
Page 58
13.3 Provided Words for Temporary Variables
The following words are provided for working with temporary
variables. The term "lamob" is used in this case to
indicate an object recalled from a termporary variable.
1ABNDSWAP ( ob --> lamob ob )
Does :: 1GETLAM ABND SWAP ;
1GETABND ( --> lamob )
Does :: 1GETLAM ABND ;
1GETLAM
... ( --> ob )
22GETLAM Returns contents of Nth lam
1GETSWAP ( ob --> lamob ob )
Does :: 1GETLAM SWAP ;
1LAMBIND ( ob --> )
Does :: 1NULLLAM{} BIND ;
1NULLLAM{} ( --> { NULLLAM } )
Returns list with one null lam
1PUTLAM
... ( ob --> )
22PUTLAM ( Stores ob into Nth lam
2GETEVAL ( --> ? )
Recalls & evaluates ob in 2nd lam
@LAM ( id --> ob TRUE )
( id --> FALSE )
Recalls lam by name, returns ob and
TRUE if id exists; FALSE otherwise
ABND ( --> )
Abandons topmost temp var env.
BIND ( ob ... { id ... } --> )
Creates new temp var env.
CACHE ( obn ... ob1 n lam --> ) Saves away n objects plus the count
n in a temporary environment, each object being bound to the
same identifier lam. The last pair has the count. )
DUMP ( NULLLAM --> ob1..obn n ) DUMP is essentially the inverse of
CACHE, BUT: it ONLY works with NULLLAM as the cached name,
and it ALWAYS does a garbage collect.
DUP1LAMBIND ( ob --> ob )
Does DUP, then 1LAMBIND
DUP4PUTLAM ( ob --> ob )
Does DUP, then 4PUTLAM
DUPTEMPENV ( --> )
Duplicates topmost temporary env.,
clearing the protection word.
GETLAM ( #n --> ob )
Returns object in #nth temp var
NULLLAM ( --> NULLLAM )
Null temporary variable name
PUTLAM ( ob #n --> )
Stores ob in #nth temp var
STO ( ob id --> )
Stores ob in named global/temp var
STOLAM ( ob id --> )
Stores ob in named temp var
Page 59
13.4 Coding Suggestions
The DEFINE feature of the RPL compiler can be used to
combine the legibility of named variables with the speed and
efficiency of null-named variables. For example:
DEFINE RclCode 1GETLAM
DEFINE StoCode 1PUTLAM
DEFINE RclName 2GETLAM
DEFINE StoName 2PUTLAM
::
...
{ NULLLAM NULLLAM }
BIND ( Binds two objects into nullnamed
temp variables 1 and 2 )
...
RclCode ( Recalls contents of last variable )
...
RclName ( Recalls contents of first variable )
...
StoCode ( Stores object in first variable )
...
ABND ( Abandons temp environment. )
;
If a large number of temporary variables are to be used
without names, here is a code-saving tip:
Replace:
...
{
NULLLAM NULLLAM NULLLAM NULLLAM
NULLLAM NULLLAM NULLLAM NULLLAM
NULLLAM NULLLAM NULLLAM NULLLAM
NULLLAM NULLLAM NULLLAM NULLLAM
NULLLAM NULLLAM NULLLAM NULLLAM
NULLLAM NULLLAM NULLLAM NULLLAM
} BIND
...
With:
NULLLAM TWENTYFOUR NDUPN
TWENTYFOUR {}N BIND
The first method takes 67.5 bytes, whereas the latter method
takes 15 bytes, so there's a savings of 52.5 bytes!
You can also use TWENTYFOUR ' NULLLAM CACHE, which is
shorter yet and does not require building the list of null
identifiers in tempob. Note, however, that CACHE adds an
extra temporary variable (to hold the count), so all of the
variable position numbers differ by one from the previous
methods.
Page 60
14. Checking Arguments
Any program object which can be executed directly by a user
should insure that the correct number and types of arguments
are present to prevent problems. If the object is
ultimately to be a library command, then it should follow
the command structure convention (see section xxx):
:: CK0 ... ; for 0 argument commands, or
:: CK<n>&Dispatch type1 action1
type2 action2
...
typen actionn
;
for <n> argument commands, where typei is a type
code and
actioni is the corresponding dispatchee for that
type combination, or
:: CKN ... ; for commands that take an number of
arguments specified
by a real number in level 1 (like PICK or ->LIST).
CK<n>&Dispatch is actually a combination of CK<n> and
CK&DISPATCH1. There are a few built-in commands (e.g. TYPE)
that use the two words instead of the combined form, but all
algebraic functions must use CK<n>&Dispatch since these
words also serve to identify the argument count used by a
function.
If an object is not intended as a library command, then it
should have the following structure:
:: CK0NOLASTWD ... ; for 0 argument programs, or
:: CK<n>NOLASTWD CK<n>&DISPATCH1 type1 action1
type2 action2
...
typen actionn
;
for <n> argument programs, or
:: CKNNOLASTWD ... ; for programs that take
arguments as specified
in level 1.
Page 61
14.1 Number of Arguments
The following words verify that from 0-5 arguments are on
the stack, and issue the "Too Few Arguments" error
otherwise.
CK0, CK0NOLASTWD No arguments required
CK1, CK1NOLASTWD One argument required
CK2, CK2NOLASTWD Two arguments required
CK3, CK3NOLASTWD Three arguments required
CK4, CK4NOLASTWD Four arguments required
CK5, CK5NOLASTWD Five arguments required
Each word CK<n>... "marks" the stack below the <n>th argument, and
if argument recovery is in effect, saves a copy of the <n> arguments in the
last argument save area. If an error
occurs that is handled by the outer loop error handler, then the stack
is cleared to the marked level (this removes any stray objects that
were not put there by the user). If the argument recovery system is active,
then the saved arguments are restored to the stack.
Any CK<n> also records the command in which it is executed, again for the
sake of the outer loop error handler, which uses the command name as
part of the error message display. A CK<n> should only be used in
library commands, and must be the first object in the command program.
CK<n>NOLASTWD does not record the command, and may be used at any point.
However, it generally not a good idea to execute these words except
* at the beginning of a user-executed object, or
* immediately after the execution of any user procedure.
User procedures should only be executed when the stack contains only user
objects; the CK<n>NOLASTWD (usually CK0NOLASTWD)
is executed immediately after the user procedure
to update the stack save mark to protect the stack results of the procedure.
This is usually done in conjunction with 0LASTOWDOB!, which clears
the command save done by the last CK<n> executed within the user
procedure, so that that command is not identified as the culprit for
any subsequent errors. Useful words for these purposes are
AtUserStack which is :: CK0NOLASTWD 0LASTOWDOB! ;
CK1NoBlame which is :: 0LASTOWDOB! CK1NOLASTWD ;
For objects that take a stack specified number of arguments, the analogs
to CK<n> and CK<n>NOLASTWD are CKN and CKNNOLASTWD. Both words check
for a real number in level 1, then check if there are that many additional
objects on the stack. The stack is marked at level 2, and only the
real number is restore by LAST ARG.
Page 62
14.2 Dispatching on Argument Type
The words CK&DISPATCH1 and CK&DISPATCH0 provide a dispatch-
by-type mechanism (the CK<n>&Dispatch words include the same
mechanism, so the following discussion applies to them as
well), that provides straightforward branching according to
the object types of up to five arguments at a time. Each
word is followed by an indefinite number of pairs of object.
Each pair consists of a binary integer or object pointer to
a binary integer, followed by any object or object pointer
(exclusive use of object pointers guarantees the fastest
dispatching):
...
CK&DISPATCH1 #type1 action1 #type2
action2 ... #typen
action3
;
The object-pair sequence must be terminated by a SEMI (;).
CK&DISPATCH1 proceeds as follows: For each typei, from type1
to typen, if typei matches the stack configuration then
execute actioni, discarding the rest of word containing
CK&DISPATCH1. If no match is found, report the error "Bad
Argument Type".
If a complete pass is made through the table without a
successful match, the CK&DISPATCH1 makes a second pass
through the table, this time stripping any tags from stack
objects and matching the remaining objects against the
required types.
Page 63
The word CK&DISPATCH0 does not perform the second pass which
strips tags. This word should only be used where it is
important to find a tagged object. The general behavior of
the HP 48 is to regard tags as being auxiliary to the tagee,
and thus CK&DISPATCH1 should be used in most cases.
A binary integer typei is nominally encoded as follows:
#nnnnn
|||||
||||+-- Level 1 argument type
|||+--- Level 2 argument type
||+---- Level 3 argument type
|+----- Level 4 argument type
+------ Level 5 argument type
Each "n" is a hexadecimal digit representing an object type,
as shown in the table below. Thus #00011 represents two
real numbers; #000A0 indicates a symbolic class object
(symb, id, or lam) in level 2 and any type of object in
level 1. There are also two-digit object type numbers,
ending in F; use of any of these consequently reduces the
total number of arguments that can be encoded in a single
typei integer. For example, #13F4F represents a real number
in level 3, an extended real in level 2, and an extended
complex in level 1.
The following table shows the hex digit values for each
argument type. The column "# name" shows the object pointer
name for the corresponding binary integer that may be used
for a single argument function. The "Binary Integers"
chapter contains a list of built-in binary integers that may
be used for various common two-argument combinations.
Value Argument # name User TYPE
----- ---------------- ------ ---------
0 Any Object any
1 Real Number real 0
2 Complex Number cmp 1
3 Character String str 2
4 Array arry 3,4
5 List list 5
6 Global Name idnt 6
7 Local Name lam 7
8 Secondary seco 8
9 Symbolic symb 9
A Symbolic Class sym 6,7,9
B Hex String hxs 10
C Graphics Object grob 11
D Tagged Object TAGGED 12
E Unit Object unitob 13
0F ROM Pointer 14
1F Binary Integer 20
2F Directory 15
3F Extended Real 21
4F Extended Complex 22
Page 64
5F Linked Array 23
6F Character 24
7F Code Object 25
8F Library 16
9F Backup 17
AF Library Data 26
BF External object1 27
CF External object2 28
DF External object3 29
EF External object4 30
Page 65
14.3 Examples
Built-in commands and other words provide good examples of
the check-and- dispatching scheme. The following is the
definition of the user command STO:
:: CK2&Dispatch
THIRTEEN XEQXSTO ( 2:any object 1:tagged object)
SIX :: STRIPTAGSl2 ?STO_HERE ; ( 2:any 1:id )
SEVEN :: STRIPTAGSl2 STO ; ( 2:any 1:lam )
NINE :: STRIPTAGSl2 SYMSTO ; ( 2:any 1:symb )
# 000c8 PICTSTO ( 2:grob 1:program [PICT] )
# 009f1 LBSTO ( 2:backup ob 1:real number )
# 008f1 LBSTO ( 2:library 1:real number )
;
Since STO is a command, it starts with CK2&Dispatch, which
verifies that there are two arguments present, saves those
arguments and the command STO for error handling, then
dispatches to one of the action objects listed in the
dispatch table. If the level one object is tagged, STO
dispatches to the word XEQSTO. For a global name (id), STO
executes :: STRIPTAGSl2 ?STO_HERE ;, which is directly
embedded in the STO program. And so forth, down to the last
choice, which is a dispatch to LBSTO when the arguments are
a library in level 2, and a real number in level 1.
The TYPE command provides an example of dispatching at a
point other than the start of a command. TYPE is a command,
but its argument counting and argument type dispatching are
separated so that the latter part can be called by other
system words that don't want to mark the stack:
::
CK1
:: CK&DISPATCH0
real %0
cmp %1
str %2
arry XEQTYPEARRY
list %5
id %6
lam %7
seco TYPESEC ( 8, 18, or 19 )
symb %9
hxs %10
grob % 11
TAGGED % 12
unitob % 13
rompointer % 14
THIRTYONE ( # ) % 20
rrp % 15
# 3F ( %% ) % 21
# 4F ( C%% ) % 22
# 5F ( LNKARRY ) % 23
# 6F ( CHR ) % 24
# 7F ( CODE ) % 25
library % 16
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backup % 17
# AF % 26 ( Library Data )
any % 27 ( external )
;
SWAPDROP
;
CK&DISPATCH0 is used here, although CK&DISPATCH1 would work
as well since tagged objects are explicitly listed in the
dispatch table. Notice also that the last typei is "any",
meaning that type 27 is returned for any object type not
previously listed.
The "inner" program (starting after the CK1) is the body of
the system word XEQTYPE.
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15. Loop Control Structures
Two types of looping structures are available - indefinite
loops and definite loops.
15.1 Indefinite Loops
Indefinite loops are constructed from combinations of the
following RPL words:
BEGIN ( --> )
Copies the interpreter pointer (RPL variable I) onto the return stack.
Also called IDUP.
UNTIL ( flag --> )
If flag is TRUE, drops the top pointer on the return stack, otherwise
copies that pointer to the interpreter pointer.
WHILE ( flag --> )
If the flag is TRUE, then does nothing. Else drops the first pointer from
the return stack, and skips the interpreter pointer past the next two
objects.
REPEAT ( --> )
-->
Copies the first pointer on the return stack to the interpreter pointer.
AGAIN ( --> )
The WHILE loop is an indefinite loop:
BEGIN
<test clause>
WHILE
<loop object>
REPEAT
The WHILE loop executes <test clause>, and if the result is
the system flag TRUE, executes the <loop object> and
repeats; otherwise it exits to past the REPEAT. The WHILE
loop never executes if the first run of <test clause>
returns FALSE.
The action of WHILE requires <loop object> to be a single
object. However, the RPL compiler automatically combines
multiple objects between WHILE and REPEAT into a program
object, so that
BEGIN
<test clause>
WHILE
ob1 ... obn
REPEAT
is actually compiled as
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BEGIN
<test clause>
WHILE
:: ob1 ... obn ;
REPEAT
Another common indefinite loop is the BEGIN...UNTIL:
BEGIN
<loop clause>
UNTIL
This loop executes at least once, as opposed to the WHILE
loop, which does not execute its loop object if the initial
test is false. The word UNTIL expects a flag (TRUE or
FALSE).
The BEGIN...AGAIN loop has no test:
BEGIN
<loop clause>
AGAIN
Terminating this loop requires an error event, or a direct
manipulation of the return stack.
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15.2 Definite Loops
Definite loops with a loop counter are achieved in RPL by
means of the DO Loop. The word DO takes two binary integer
objects from the stack, and stores the top object as the
index and the other as the stopping value in a special
DoLoop environment. DO also copies the interpreter pointer
onto the return stack. DoLoop environments are stacked, so
that they can be nested indefinitely. The topmost index is
recalled by INDEX@; the index in the second environment by
JINDEX@. The topmost stopping value is available via
ISTOP@.
DO's counterparts are LOOP and +LOOP. LOOP increments the
index value in the topmost DoLoop environment; then, if the
(new) value is greater than or equal to the stopping value,
LOOP drops the top pointer from the return stack and removes
the topmost DoLoop environment. Otherwise, LOOP acts copies
the top return stack pointer to the interpreter pointer.
The standard form of a DoLoop is
stop start DO <loop clause> LOOP,
which executes <loop clause> for each value of an index from
start to stop-1.
+LOOP is similar to LOOP, except that it takes a binary
integer from the stack and increments the loop counter by
that amount rather than 1.
15.2.1 Provided_Words
The following words are provided for use with DO loops.
Words marked with * are not recognized as special by the RPL
compiler, so you should include compiler directives to
prevent warning messages. For example, #1+_ONE_DO can be
followed by (DO) which matches the following LOOP for the
sake of the compiler but does not generate any compiled
code.
#1+_ONE_DO * ( #finish --> )
Equivalent to #1+ ONE DO; commonly used to execute a loop
#finish times.
DO ( #finish #start --> )
Begins DO loop
DROPLOOP * ( ob --> )
Performs DROP, then LOOP
DUP#0_DO * ( # --> # )
Begins # ... #0 DO loop
DUPINDEX@ ( ob --> ob ob #index )
Does DUP, then returns value of index in topmost DoLoop env.
ExitAtLOOP ( --> )
Stores zero in stopping value of topmost DoLoop environment
INDEX@ ( --> #index )
Returns index of topmost DoLoop environment
INDEX@#- ( # --> #' )
Subtracts index value of topmost
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DoLoop environment from #
INDEXSTO ( # --> )
Stores # as index of top DoLoop environment
ISTOP@ ( --> #stop )
Returns stop value of the topmost DoLoop environment
ISTOPSTO ( # --> )
Stores new stop value in the topmost DoLoop environment
JINDEX@ ( --> #index )
Returns index of second DoLoop environment
LOOP ( --> )
End of loop structure
NOT_UNTIL * ( flag --> )
End of loop structure
ONE_DO * ( #finish --> )
Begins #1...#finish DO loop
OVERINDEX@ ( ob1 ob2 --> ob1 ob2 ob1 #index )
Does OVER, then returns value of
index in topmost DoLoop environment
SWAPINDEX@ ( ob1 ob2 --> ob2 ob1 #index )
Does SWAP, then returns value of index in topmost
DoLoop environment
SWAPLOOP * ( ob1 ob2 --> ob2 ob1 )
Does SWAP, then LOOP
ZEROISTOPSTO ( --> )
Stores zero as the stop value in the topmost DoLoop
environment
ZERO_DO * ( #finish --> )
Begins DO loop from #0 to #finish
toLEN_DO ( {list} --> {list} )
Begins DO loop from #1 of elements in list to stop value
#number-of-elements+1.
15.2.2 Examples
FIVE ZERO
DO
INDEX@
LOOP
This returns the values:
#00000 #00001 #00002 #00003 #00004
The following sequence displays each of the elements (up to 8) of
a list of strings on a separate display line.
DUPLENCOMP
ONE_DO (DO)
DUP INDEX@ NTHCOMPDROP
INDEX@ DISPN
LOOP
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A more compact version uses toLEN_DO:
toLEN_DO (DO)
DUP INDEX@ NTHCOMPDROP
INDEX@ DISPN
LOOP
Another version is slightly faster, since it avoids repeated extraction
of list elements:
INNERCOMP
#1+_ONE_DO (DO)
INDEX@ DISPN
LOOP
This version displays the elements in reverse order relative to the previous
versions.
Page 72
16. Error Generation & Trapping
The RPL error handling sub-system is invoked by execution of
the word ERRJMP, that is, when a procedure class object
wishes to generate an error, it executes ERRJMP (probably
after setting the values of ERROR and ERRNAME). The
mechanics of ERRJMP will be described later.
16.1 Trapping: ERRSET and ERRTRAP
RPL provides procedure objects with the capability to
intercept execution of the error handling sub-system, that
is, trap an error generated by an object which is lower on
the threaded order. This capability is made available via
the built-in objects ERRSET and ERRTRAP used in the
following way:
:: ... ERRSET <suspect object> ERRTRAP <if-error object> ... ;
In the above, an error generated by <suspect object> is to
be trapped. <if-error object> denotes the object to be
executed if <suspect object> generates an error. The exact
algorithm is: If <suspect object> generates an error, then
continue execution at <if-error object>; else, continue
execution beyond <if-error object>.
The action of <if-error object> is completely flexible; when
<if-error object> gets control, it may examine the values of
ERROR and ERRNAME to determine whether or not it is even
concerned with the current error. If not, it may simply re-
start the sub-system by executing ERRJMP. If so, it may
decide to handle the error, that is, clear both ERROR and
ERRNAME and NOT restart the sub-system. It may also disable
execution of the remainder of the program (perhaps via
RDROP).
Note that throughout (normal) execution of <suspect object>,
an object pointer to the following ERRTRAP is somewhere in
the runstream.
16.2 Action of ERRJMP
When an RPL procedure wants to initiate an error, it
executes ERRJMP, which the error handling sub-system.
ERRJMP cycles through the RUNSTREAM from the interpreter
pointer I up through the return stack searching for an error
trap. Specifically, ERRJMP removes pending program bodies
from the RUNSTREAM until it finds one whose first element is
an object pointer addressing ERRTRAP (this program body may
correspond to a return stack level as well as the
interpreter pointer I). It then SKIPs over the object
pointer to ERRTRAP and continues execution beyond it (at the
<if-error object>).
Note, therefore, that ERRTRAP is only executed if <suspect
object> terminates without generating an error; in this
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case, ERRTRAP will, among other things, SKIP <if-error
object> and continue execution beyond it.
If a procedure is not merely passing along an error that it
did not initiate, its invokation of ERRJMP should be
preceded by execution of ERRORSTO, which stores an error
number in a special system location. ERROR@ returns the
stored error number, which error traps can use to determine
if they want to handle a particular error. The error number
is stored and returned as a binary integer; the high-order
12 bits of the number represent the Library ID of the
library containing the error message, and the remaining bits
indicate the error number within the library's message
table.
16.3 The Protection Word
Each temporary environment and each DoLoop environment has a
protection word. The sole reason for the existence of this
protection word is to allow the error handling sub-system to
distinguish temporary and DoLoop environments that were in
existence at the time an error trap was set from those which
came into being after the error trap was set. For example,
consider the following:
::
...
{ NULLLAM } BIND
...
TEN ZERO DO
ERRSET ::
...
{ NULLLAM } BIND
...
FIVE TWO DO
<procedure>
LOOP
ABND
;
ERRTRAP
:: "Procedure Failed" FlashMsg ;
LOOP
...
ABND
...
;
If <procedure> generates an error, then this error will be
trapped by the word or secondary following ERRTRAP.
However, the inner DoLoop and temporary environments must be
deleted so that the outer procedure has available the
correct DoLoop parameters and local variables. The
protection word serves to abet this function.
ERRSET increments the protection word in the topmost
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temporary environment and the topmost DoLoop environment.
These topmost environments therefore have a non-zero
protection word. (DO and BIND always initialize the
protection word to zero).
ERRTRAP and ERRJMP delete temporary and DoLoop environments
(from the first to the last) until, in both cases, they find
one with a non-zero protection word, which is then
decremented. Therefore, whenever either ERRJMP executes at
<if-error object> or ERRTRAP executes past <if-error
object>, only temporary and DoLoop environments which
existed at the ERRSET will be present.
Note especially that the protection word is more than just a
switch so as to allow a practically indeterminant level of
nesting of error traps.
The example above is actually a poorly formed error trap -
the code should actually determine what the error was, and
take action accordingly. The word ERROR@ may be used to
recall which error occurred. The error numbers correspond
to the message numbers - see the message table in appendix A
of the "HP48 Programmers Reference Manual".
16.4 Error Words
The following words are provided for error management:
ABORT ( --> )
Does ERRORCLR and ERRJMP
DO#EXIT ( msg# --> )
Stores a new error number and executes ERRJMP;
also executes AtUserStack
Puts the object ERRJMP on the stack
ERRBEEP ( --> )
Generates an error beep
ERRJMP ( --> )
Invokes error handling subsystem
ERROR@ ( --> # )
Returns the current error number
ERRORCLR ( --> )
Stores zero as the error number
ERROROUT ( # --> )
Stores a new error number and does ERRJMP
ERRORSTO ( # --> )
Stores new error number
ERRTRAP ( --> )
Skips next object in runstream.
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17. Test and Control
This chapter reviews words related to the flow of control:
conditional and unconditional branches and the associated
test words.
17.1 Flags and Tests
TRUE and FALSE are built-in objects that are recognized by
test words as flags for branching decisions. The following
words create or combine flags:
AND ( flag1 flag2 --> flag )
If flag1 and flag2 are both TRUE then TRUE else FALSE.
FALSE ( --> FALSE )
Puts the FALSE flag on the stack.
FALSETRUE ( --> FALSE TRUE )
FalseFalse ( --> FALSE FALSE )
OR ( flag1 flag2 --> flag )
If either flag1 or flag2 is TRUE then TRUE else FALSE.
ORNOT ( flag1 flag2 --> flag3 )
Logical OR followed by logical NOT.
NOT ( flag --> flag' )
If flag is TRUE then FALSE else TRUE.
NOTAND ( flag1 flag2 --> flag3 )
Logical NOT, then logical AND.
ROTAND ( flag1 ob flag2 --> ob flag3 )
Does ROT, then logical AND.
TRUE ( --> TRUE )
Puts the TRUE flag on the stack.
TrueFalse ( --> TRUE FALSE )
TrueTrue ( --> TRUE TRUE )
XOR ( flag1 flag2 --> flag )
If both flag1 and flag2 are either TRUE or FALSE then FALSE, else TRUE.
COERCEFLAG ( TRUE --> %1 )
( FALSE --> %0 )
Converts a system flag to a real number flag.
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17.1.1 General_Object_Tests
The following words test object type and equality:
EQ ( ob1 ob2 --> flag )
If objects ob1 and ob2 are the same object, i.e. occupy the same
physical space in memory, then TRUE else FALSE.
EQUAL ( ob1 ob2 --> flag )
where ob1 and ob2 are not primitive code objects. If objects ob1 and
ob2 are the same then TRUE else FALSE (this word is the system
equivalent of the user RPL command SAME)
2DUPEQ ( ob1 ob2 --> ob1 ob2 flag )
Returns TRUE if ob1 and ob2 have the same physical address.
EQOR ( flag1 ob1 ob2 --> flag2 )
Does EQ, then logical OR.
EQUALOR ( flag1 ob1 ob2 --> flag2 )
Does EQUAL, the logical OR.
EQOVER ( ob1 ob2 ob3 --> ob1 flag ob1 )
Does EQ, then OVER.
EQUALNOT ( ob1 ob2 --> flag )
Returns FALSE if ob1 is equal to ob2.
The following words test an object's type. Words of the
form TYPE...? have a stack diagram ( ob --> flag ); those
of the form DTYPE...? or DUPTYPE...? duplicate the object
first ( ob --> ob flag ).
Test Words Object type
TYPEARRY? array
DTYPEARRY?
DUPTYPEARRY?
TYPEBINT? binary integer
DUPTYPEBINT?
TYPECARRY? complex array
TYPECHAR? character
DUPTYPECHAR?
TYPECMP? complex number
DUPTYPECMP?
TYPECOL? program
DTYPECOL?
DUPTYPECOL?
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TYPECSTR? string
DTYPECSTR?
DUPTYPECSTR?
TYPEEXT? unit
DUPTYPEEXT?
TYPEGROB? graphics object
DUPTYPEGROB?
TYPEHSTR? hex string
DUPTYPEHSTR?
TYPEIDNT? identifier (global name)
DUPTYPEIDNT?
TYPELAM? temporary identifier (local name)
DUPTYPELAM?
TYPELIST? list
DTYPELIST?
DUPTYPELIST?
TYPERARRY? real array
TYPEREAL? real number
DTYPEREAL?
DUPTYPEREAL?
TYPEROMP? ROM pointer (XLIB name)
DUPTYPEROMP?
TYPERRP? Directory
DUPTYPERRP?
TYPESYMB? Symbolic
DUPTYPESYMB?
TYPETAGGED? Tagged
DUPTYPETAG?
17.1.2 Binary_Integer_Comparisons
The following words compare binary integers, returning TRUE
or FALSE. Equality is tested in the sense of EQUAL (not EQ).
Ordering treats all binary integers as unsigned. Some of
these words are also available in combination with case
words (see below).
#= ( # #' --> flag ) TRUE if # = #'.
#<> ( # #' --> flag ) TRUE if # <> #' (not equal).
#0= ( # --> flag ) TRUE if # = 0
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#0<> ( # --> flag ) TRUE if # <> 0
#< ( # #' --> flag ) TRUE if # < #'
#> ( # #' --> flag ) TRUE if # > #'
2DUP#< ( # #' --> # #' flag ) TRUE if # < #'
2DUP#= ( # #' --> # #' flag ) TRUE if # = #'
DUP#0= ( # --> # flag ) TRUE if # = #0
DUP#1= ( # --> # flag ) TRUE if # = #1
DUP#0<> ( # --> # flag ) TRUE if # <> #0
DUP#1= ( # --> # flag ) TRUE if # = #1
DUP#<7 ( # --> # flag ) TRUE if # < #7
DUP%0= ( % --> % flag ) TRUE if % = %0
ONE#> ( # --> flag ) TRUE if # > #1
ONE_EQ ( # --> flag ) TRUE if # is ONE
OVER#> ( # #' --> # flag ) TRUE if # > #'
OVER#0= ( # ob --> # ob flag ) TRUE if # is #0
OVER#< ( # #' --> # flag ) TRUE if # > #'
OVER#= ( # #' --> # flag ) TRUE if # = #'
OVER#> ( # #' --> # flag ) TRUE if # < #'
17.1.3 Decimal_Number_Tests
The following words compare real, extended real, and complex
numbers, returning TRUE or FALSE.
%< ( % %' --> flag ) TRUE if % < %'
%<= ( % %' --> flag ) TRUE if % <= %'
%<> ( % %' --> flag ) TRUE if % <> %'
%= ( % %' --> flag ) TRUE if % = %'
%> ( % %' --> flag ) TRUE if % > %'
%>= ( % %' --> flag ) TRUE if % >= %'
%0< ( % --> flag ) TRUE if % < 0
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%0<> ( % --> flag ) TRUE if % <> 0
%0= ( % --> flag ) TRUE if % = 0
%0> ( % --> flag ) TRUE if % > 0
%0>= ( % --> flag ) TRUE if % >= 0
%%0<= ( %% %%' --> flag ) TRUE if %% <= %%'
%%0<> ( %% --> flag ) TRUE if %% <> 0
%%0= ( %% --> flag ) TRUE if %% = 0
%%0> ( %% --> flag ) TRUE if %% > 0
%%0>= ( %% --> flag ) TRUE if %% >= 0
%%> ( %% %%' --> flag ) TRUE if %% > %%'
%%>= ( %% %%' --> flag ) TRUE if %% >= %%'
%%<= ( %% %%' --> flag ) TRUE if %% <= %%'
C%%0= ( C%% --> flag ) TRUE if C%% = (%%0,%%0)
C%0= ( C% --> flag ) TRUE if C% = (0,0)
17.2 Words that Operate on the Runstream
In many cases, it is desirable to interrupt the normal
threaded order of execution, and insert additional objects
or skip others in the runstream. The following words are
provided for these purposes.
' ( --> ob )
This is the RPL analogue of the Lisp QUOTE and is one of
the most fundamental control objects, allowing the
evaluation of an object to be postponed. More precisely,
assumes that the topmost body in the RUNSTREAM is non-
empty, i.e. the interpreter pointer does not point at a
SEMI; and (1) If the next object in the runstream is an
object, then pushes this object onto the data stack and
moves the interpreter pointer to the next object; (2) If
the next object is an object pointer, then pushes the
pointee on the data stack and similarly skips to the next
object. As an example, evaluation of the secondaries
:: # 3 # 4 SWAP ; and :: # 3 # 4 ' SWAP EVAL ;
both produce the same result.
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'R ( --> ob )
If the object pointed to by the top pointer on the return
stack (i.e. the first element in the second body in the
runstream) is an object, then 'R pushes this object onto
the data stack, and advances the pointer to the next
object in the same composite. If the pointer points to an
object pointer whose pointee is not SEMI, then pushes the
pointee onto the data stack, and similarly advances the
return stack pointer. If the pointee is SEMI, then If the
first element in the second body in the runstream is an
object pointer to SEMI, then pushes a null secondary onto
the data stack and does not advance the return stack
pointer. 'R is useful in defining prefix operators. For
example, assume that PREFIXSTO is defined as :: 'R STO ;
Then the sequence PREFIXSTO FRED ANOTHEROBJECT would first
push FRED onto the data stack and then execute STO, after
which execution resumes at ANOTHEROBJECT.
ticR ( --> ob TRUE | FALSE )
This word works similarly to 'R, except that it returns a
flag to indicate whether the end of the top return stack
composite has been reached. That is, if the top return
stack pointer points to an object pointer to SEMI, then
ticR pops the return stack and returns only FALSE.
Otherwise return the next object from the composite and
TRUE, while advancing the return stack pointer to the next
object.
>R ( :: --> )
Inserts the body of :: into the runstream, just below the
top one. (That is, pushes a pointer to the body of ::
onto the return stack). An example of its use is
:: ' :: <foo> ; >R <bar> ;
which will, when executed, cause <bar> to be executed
before <foo>.
R> ( --> :: )
Creates a program object from the composite body pointed
to by the top return stack pointer, and pushes the program
on the data stack and pops the return stack. Example:
:: :: R> EVAL <foo> ; <bar> ;
which, when executed, will cause <bar> to be executed
before <foo>.
R@ ( --> :: )
Same as R> except that the return stack is not popped.
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RDROP ( --> )
Pops the return stack.
IDUP ( --> )
Duplicates the top body in the runstream. (That is, pushes
the RPL variable I onto the return stack).
COLA ( --> )
Assuming that the interpreter pointer is pointing at an
object other than SEMI, COLA drops the remainder of the
program body past the object and executes the object.
This provides for efficient tail recursion; the efficiency
is gained in that COLA can be used to avoid excessive
buildup of pending returns. An example of its use is in a
definition of factorial:
fact: :: { LAM x } BIND # 1 factpair ABND
;
factpair: :: LAM x #0= ?SEMI
LAM x #* LAM x #1- ' LAM x
STO COLA factpair
;
In this example, the importance of COLA is in its
occurrence before factpair in the definition of factpair.
Without this use, computing n! would require n return
stack levels, which, when the computation was completed,
would merely be popped off (since their bodies would be
empty). With the inclusion of COLA, the definition uses a
fixed maximum number of levels, independent of the
argument to the function.
?SEMI ( flag --> )
Exits the current program if flag is TRUE.
?SEMIDROP ( ob TRUE --> ) or ( FALSE --> )
Drops ob if flag is TRUE; exits the current program if
flag is FALSE.
?SKIP ( flag --> )
If flag is TRUE, skips the next object following ?SKIP.
NOT?SEMI ( flag --> )
Exits the current program if flag is FALSE.
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17.3 If/Then/Else
The fundamental RPL if/then/else capability is provided by
means of the words RPIT and RPITE:
RPITE ( flag ob1 ob2 --> ? )
If flag is TRUE then drop flag and ob2 and EVALuate ob1,
else drop flag and ob1 and EVALuate ob2. The RPL
expression
' <foo> ' <bar> RPITE
is equivalent to the FORTH expression
IF <foo> ELSE <bar> THEN
RPIT ( flag ob --> ? )
If flag is TRUE then drop flag and EVALuate ob, else just
drop flag and ob. The RPL expression
' <foo> RPIT
is equivalent to the FORTH expression
IF <foo> THEN
However, prefix versions of these words are also available,
and are more commonly used than the postfix forms:
IT ( flag --> )
If flag is TRUE then execute the next object in the
runstream; otherwise skip that object. For example,
DUPTYPEREAL? IT :: %0 %>C% ;
converts a real number to a complex number; does nothing
if the argument is not a real number.
ITE ( flag --> )
If flag is TRUE the execute the next object in the
runstream, and skip the second object; otherwise skip the
next object and execute the second. For example,
DUPTYPELIST? ITE INNERCOMP ONE
takes a list apart, leaving the count on the stack; for
any other type of argument, push a binary integer #1 on
the stack.
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The converse of IT is
?SKIP ( flag --> )
If flag is TRUE, skip the next object in the runstream;
otherwise, execute it.
There is also an unconditional skip:
SKIP ( --> )
Skips over the next object in the runstream and continues
execution beyond it. The sequence SKIP ; is a NOP.
Combination Words:
Word Stack Equivalent
#0=ITE ( # --> ) #0= ITE
#<ITE ( # --> ) #0< ITE
#=ITE ( # --> ) #= ITE
#>ITE ( # --> ) #> ITE
ANDITE ( flag flag' --> ) AND ITE
DUP#0=ITE ( # --> # ) DUP #0= ITE
EQIT ( ob1 ob2 --> ) EQ IT
EQITE ( ob ob' --> ) EQ ITE
DUP#0=IT ( # --> # ) DUP #0= IT
SysITE ( # --> )
UserITE ( # --> )
17.4 CASE words
The word case is a combination of ITE, COLA and SKIP. That
is, case takes a flag from the stack; if TRUE, case executes
the object that follows it in the runstream while popping
the return stack to the interpreter pointer, discarding the
rest of the program that follows the object (like COLA). If
FALSE, case skips the next object and continues with the
program (like SKIP). For example, the following program
executes different objects according to the value of a
binary integer on the stack:
:: DUP #0= case ZEROCASE
DUP ONE #= case ONECASE
DUP TWO #= case TWOCASE
...
;
Page 84
There are several words that contain case as part of their
definitions. The above example can be written more
compactly using OVER#=case:
:: ZERO OVER#=case ZEROCASE
ONE OVER#=case ONECASE
TWO OVER#=case TWOCASE
...
;
The actions of the words listed below are generally
sufficiently clear from their names. The names have (up to)
three parts: an initial part, then "case", then a final
part. The initial part indicates what is done before the
case action, i.e. "xxxcase..." is equivalent to "xxx
case...". Words that have a final part after "case" are of
two types. For one type, the final part indicates the
conditionally executed object itself, i.e. "...caseyyy" is
equivalent to "...case yyy." In the other type, the final
part is a word or words that are incorporated into the
following object. caseDROP and casedrop are of the first
type and second type, respectively. caseDROP is equivalent
to case DROP; casedrop is like case with a DROP incorporated
into the next object. That is,
Words that COLA or SKIP the next object:
#=casedrop ( # # --> )
( # #' --> # )
Should be named OVER#=casedrop.
%1=case ( % --> )
%0=case ( % --> flag )
ANDNOTcase ( flag1 flag2 --> )
ANDcase ( flag1 flag2 --> )
case2drop ( ob1 ob2 TRUE --> )
( FALSE --> )
casedrop ( ob TRUE --> )
( FALSE --> )
DUP#0=case ( # --> # )
DUP#0=csedrp ( # --> # ) # <> #0
( # --> ) # = #0
EQUALNOTcase ( ob ob' --> )
EQUALcase ( ob ob' --> )
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EQUALcasedrp ( ob ob' ob' --> )
( ob ob' ob'' --> ob )
EQcase ( ob1 ob2 --> )
NOTcase ( flag --> )
NOTcasedrop ( ob FALSE --> )
( TRUE --> )
ORcase ( flag1 flag2 --> )
OVER#=case ( # #' --> # )
Case words that either exit or continue with the next object:
caseDoBadKey ( flag --> ) Exit via DoBadKey
caseDrpBadKey ( ob TRUE --> ) Exit via DoBadKey
( FALSE --> )
case2DROP ( ob1 ob2 TRUE --> )
( FALSE --> )
caseDROP ( ob TRUE --> )
( FALSE --> )
caseFALSE ( TRUE --> FALSE )
( FALSE --> )
caseTRUE ( TRUE --> TRUE )
( FALSE --> )
casedrpfls ( ob TRUE --> FALSE )
( FALSE --> )
case2drpfls ( ob1 ob2 TRUE --> FALSE )
( FALSE --> )
casedrptru ( ob TRUE --> TRUE )
( FALSE --> )
DUP#0=csDROP ( #0 --> )
( # --> # ) # <> 0.
NOTcaseTRUE ( FALSE --> TRUE )
( TRUE --> )
Page 86
18. Stack Operations
The words listed in this chapter perform single or multiple
stack operations.
2DROP ( ob1 ob2 --> )
2DROP00 ( ob1 ob2 --> #0 #0 )
2DROPFALSE ( ob1 ob2 --> FALSE )
2DUP ( ob1 ob2 --> ob1 ob2 ob1 ob2 )
2DUP5ROLL ( ob1 ob2 ob3 --> ob2 ob3 ob2 ob3 ob1 )
2DUPSWAP ( ob1 ob2 --> ob1 ob2 ob2 ob1 )
2OVER ( ob1 ob2 ob3 ob4 --> ob1 ob2 ob3 ob4 ob1 ob2 )
2SWAP ( ob1 ob2 ob3 ob4 --> ob3 ob4 ob1 ob2 )
3DROP ( ob1 ob2 ob3 --> )
3PICK ( ob1 ob2 ob3 --> ob1 ob2 ob3 ob1 )
3PICK3PICK ( ob1 ob2 ob3 --> ob1 ob2 ob3 ob1 ob2 )
3PICKOVER ( ob1 ob2 ob3 --> ob1 ob2 ob3 ob1 ob3 )
3PICKSWAP ( ob1 ob2 ob3 --> ob1 ob2 ob1 ob3 )
3UNROLL ( ob1 ob2 ob3 --> ob3 ob1 ob2 )
4DROP ( ob1 ob2 ob3 ob4 --> )
4PICK ( ob1 ob2 ob3 ob4 --> ob1 ... ob4 ob1 )
4PICKOVER ( ob1 ob2 ob3 ob4 --> ob1 ob2 ob3 ob4 ob1 ob4 )
4PICKSWAP ( ob1 ob2 ob3 ob4 --> ob1 ob2 ob3 ob1 ob4 )
4ROLL ( ob1 ob2 ob3 ob4 --> ob2 ob3 ob4 ob1 )
4UNROLL ( ob1 ob2 ob3 ob4 --> ob4 ob1 ob2 ob3 )
4UNROLL3DROP ( ob1 ob2 ob3 ob4 --> ob4 )
4UNROLLDUP ( ob1 ob2 ob3 ob4 --> ob4 ob1 ob2 ob3 ob3 )
4UNROLLROT ( ob1 ob2 ob3 ob4 --> ob4 ob3 ob2 ob1 )
5DROP ( ob1 ... ob5 --> )
5PICK ( ob1 ... ob5 --> ob1 ... ob5 ob1 )
5ROLL ( ob1 ... ob5 --> ob2 ... ob5 ob1 )
5ROLLDROP ( ob1 ... ob5 --> ob2 ... ob5 )
5UNROLL ( ob1 ... ob5 --> ob5 ob1 ... ob4 )
6DROP ( ob1 ... ob6 --> )
6PICK ( ob1 ... ob6 --> ob1 ... ob6 ob1 )
6ROLL ( ob1 ... ob6 --> ob2 ... ob6 ob1 )
7DROP ( ob1 ... ob7 --> )
7PICK ( ob1 ... ob7 --> ob1 ... ob7 ob1 )
7ROLL ( ob1 ... ob7 --> ob2 ... ob7 ob1 )
8PICK ( ob1 ... ob8 --> ob1 ... ob8 ob1 )
8ROLL ( ob1 ... ob8 --> ob2 ... ob8 ob1 )
8UNROLL ( ob1 ... ob8 --> ob8 ob1 ... ob7 )
DEPTH ( ob1 ... obn ... --> #n )
DROP ( ob --> )
DROPDUP ( ob1 ob2 --> ob1 ob1 )
DROPFALSE ( ob --> FALSE )
DROPNDROP ( ... # ob ) Drops ob, then # objects
DROPONE ( ob --> #1 )
DROPOVER ( ob1 ob2 ob3 --> ob1 ob2 ob1 )
DROPRDROP ( ob --> ) Drops ob, and pops 1 return stk level
DROPROT ( ob1 ob2 ob3 ob4 --> ob2 ob3 ob1 )
DROPSWAP ( ob1 ob2 ob3 --> ob2 ob1 )
DROPSWAPDROP ( ob1 ob2 ob3 --> ob2 )
DROPTRUE ( ob --> TRUE )
DROPZERO ( ob --> #0 )
DUP ( ob --> ob ob )
DUP#1+PICK ( ... #n --> ... #n obn )
DUP3PICK ( ob1 ob2 --> ob1 ob2 ob2 ob1 )
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DUP4UNROLL ( ob1 ob2 ob3 --> ob3 ob1 ob2 ob3 )
DUPDUP ( ob --> ob ob ob )
DUPONE ( ob --> ob ob #1 )
DUPPICK ( ... #n --> ... #n obn-1 )
DUPROLL ( ... #n --> ... #n obn-1 )
DUPROT ( ob1 ob2 --> ob2 ob2 ob1 )
DUPTWO ( ob --> ob ob #2 )
DUPUNROT ( ob1 ob2 --> ob2 ob1 ob2 )
DUPZERO ( ob --> ob ob #2 )
N+1DROP ( ob ob1 ... obn #n --> )
NDROP ( ob1 ... obn #n --> )
NDUP ( ob1 ... obn #n --> ob1 ... obn ob1 ... obn )
NDUPN ( ob #n --> ob ... ob )
ONEFALSE ( --> #1 FALSE )
ONESWAP ( ob --> #1 ob )
OVER ( ob1 ob2 --> ob1 ob2 ob1 )
OVER5PICK ( v w x y z --> v w x y z y v )
OVERDUP ( ob1 ob2 --> ob1 ob2 ob1 ob1 )
OVERSWAP ( ob1 ob2 --> ob2 ob1 ob1 )
OVERUNROT ( ob1 ob2 --> ob1 ob1 ob2 )
PICK ( obn ... #n --> ... obn )
ROLL ( obn ... #n --> ... obn )
ROLLDROP ( obn ... #n --> ... )
ROLLSWAP ( obn ... ob #n --> ... obn ob )
ROT ( ob1 ob2 ob3 --> ob2 ob3 ob1 )
ROT2DROP ( ob1 ob2 ob3 --> ob2 )
ROT2DUP ( ob1 ob2 ob3 --> ob2 ob3 ob1 ob3 ob1 )
ROTDROP ( ob1 ob2 ob3 --> ob2 ob3 )
ROTDROPSWAP ( ob1 ob2 ob3 --> ob3 ob2 )
ROTDUP ( ob1 ob2 ob3 --> ob2 ob3 ob1 ob1 )
ROTOVER ( ob1 ob2 ob3 --> ob2 ob3 ob1 ob3 )
ROTROT2DROP ( ob1 ob2 ob3 --> ob3 )
ROTSWAP ( ob1 ob2 ob3 --> ob2 ob1 ob3 )
SWAP ( ob1 ob2 --> ob2 ob1 )
SWAP2DUP ( ob1 ob2 --> ob2 ob1 ob2 ob1 )
SWAP3PICK ( ob1 ob2 ob3 --> ob1 ob3 ob2 ob1 )
SWAP4PICK ( ob1 ob2 ob3 ob4 --> ob1 ob2 ob4 ob3 ob4 )
SWAPDROP ( ob1 ob2 --> ob2 )
SWAPDROPDUP ( ob1 ob2 --> ob2 ob2 )
SWAPDROPSWAP ( ob1 ob2 ob3 --> ob3 ob1 )
SWAPDROPTRUE ( ob1 ob2 --> ob2 TRUE )
SWAPDUP ( ob1 ob2 --> ob2 ob1 ob1 )
SWAPONE ( ob1 ob2 --> ob2 ob1 #1 )
SWAPOVER ( ob1 ob2 --> ob2 ob1 ob2 )
SWAPROT ( ob1 ob2 ob3 --> ob3 ob2 ob1 )
SWAPTRUE ( ob1 ob2 --> ob2 ob1 TRUE )
UNROLL ( ... ob #n --> ob ... )
UNROT ( ob1 ob2 ob3 --> ob3 ob1 ob2 )
UNROT2DROP ( ob1 ob2 ob3 --> ob3 )
UNROTDROP ( ob1 ob2 ob3 --> ob3 ob1 )
UNROTDUP ( ob1 ob2 ob3 --> ob3 ob1 ob2 ob2 )
UNROTOVER ( ob1 ob2 ob3 --> ob3 ob1 ob2 ob1 )
UNROTSWAP ( ob1 ob2 ob3 --> ob3 ob2 ob1 )
ZEROOVER ( ob --> ob #0 ob )
reversym ( ob1 ... obn #n --> obn ... ob1 #n )
Page 88
19. Memory Operations
The words presented in this chapter manipulate directories,
variables, and system ram.
19.1 Temporary Memory
The user word NEWOB creates a new copy of an object in
temporary memory. There are a few internal variations on
this theme:
CKREF ( ob --> ob' )
If ob is in TEMPOB, is not embedded
in a composite object, and is not
referenced, then does nothing. Otherwise
copies ob to TEMPOB and returns the copy.
INTEMNOTREF? ( ob --> ob flag )
If the input object is in TEMPOB area,
is not embedded in a composite object,
and is not referenced, returns ob and
TRUE, otherwise returns ob and FALSE.
TOTEMPOB ( ob --> ob' )
Copies ob into TEMPOB and returns pointer
to the new ob.
19.2 Variables and Directories
The system RPL basis of user STO and RCL is the words STO,
CREATE, and @:
CREATE ( ob id --> )
Creates a RAM-WORD with ob as its object part and the NAME
FORM from id as its name part, in the current directory.
An error occurs if ob is or contains the current directory
("Directory Recursion"). Assumes that ob is not a
primitive code object.
STO ( ob id --> )
( ob lam --> )
In the lam case, the temporary identifier lam is re-bound
to ob. The binding is to the first such temporary
identifier object matching lam in the Temporary
Environment area (searching from the first temporary
environment to the last). An error is returned if lam is
unbound. In the id case, STO attempts to match id to the
name part of a global variable. If resolution is
unsuccessful, STO creates a variable with ob as its object
part and the name form from id as its name part, in the
current directory. If resolution is successful, then ob
replaces the object part of the resolved variable. If any
updatable system object pointers reference the object part
of the resolved variable, then the object part is placed
into the temporary object area prior to the replacement
and all affected updatable system object pointers are
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adjusted to reference the copy of the object part in the
temporary object area. For the id case, STO assumes that
ob is not a primitive code object.
@ ( id --> ob TRUE )
( id --> FALSE )
( lam --> ob TRUE )
( lam --> FALSE )
In the lam case, @ attempts to match lam to the temporary
identifier object part of a binding in the Temporary
Environment area (searching from the first temporary
environment to the last). If successful, then the object
bound to lam is returned along with a TRUE flag; else, a
FALSE flag is returned. In the id case, @ attempts to
match id to the name part of a global variable, starting
in the current directory, and working up through parent
directories if necessary. If the resolution is
unsuccessful, then a FALSE flag is returned. Otherwise,
the object part of the resolved variable is returned with
a TRUE flag.
One difficulty in using STO and @ is that they make no
distinctions for built-in commands; with SIN as its (object)
argument, STO will blithely copy the entire body of SIN into
a variable. @ then would recall that undecompilable
program. For this reason, it is better to use SAFESTO and
SAFE@, which work like STO and @ except that they
automatically convert ROM bodies into XLIB names (SAFESTO)
and back again (SAFE@).
Additional extensions are:
?STO_HERE ( ob id --> )
( ob lam --> )
This is the system version of user STO. It is the same as
SAFESTO, except that for global variables, it a) stores
only in the current directory; and b) will not overwrite a
stored directory.
SAFE@_HERE ( id --> ob TRUE )
( id --> FALSE )
( lam --> ob TRUE )
( lam --> FALSE )
Same as SAFE@, except for global variables the search is restricted to the
current directory.
Other related words:
PURGE ( id --> ) Purges variable specified by id; does
no type check on
stored object.
XEQRCL ( id --> ob ) Same as SAFE@ for global variables,
but errors
if variable is nonexistent
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XEQSTOID ( ob id --> ) Alternate name for ?STO_HERE
19.2.1 Directories A directory (abbreviated "rrp" from its
original name "ramrompair") is an object whose body contains
a linked-list of global variables--named objects referenced
by global names. The body also contains a library ID number
that associates ("attaches") a library object with the
directory so that the library's commands follow the
directory's variables in the name compilation search order.
A directory may be "rooted", i.e. stored in a global
variable (which may be within another directory body), in
which case its variable's names are available for
compilation. The particular directory in which a name
resolution search begins is called the "current directory,"
or the "context directory;" this directory is specified by
the contents of a system RAM location. An unrooted
directory (in tempob or in a port, for example), should
never be selected as the context directory. Nor can there
be any references within a directory in tempob; a directory
is not a composite object, so garbage collection cannot work
properly if such references exist. For this reason, an
internally referenced directory should not be removed by
PURGE--use XEQPGDIR instead.
In addition to the context, another system RAM location
identifies the "stopsign" directory, which is acts as the
ending point for a name resolution search much as the
context directory is the starting point. By using the
stopsign, you can restrict name resolution searches to a
specific range; however, you should use error traps to
insure that the stopsign is reset to the home directory when
an error occurs.
The home directory (aka "sysramrompair") is the default for
both context and stopsign. This is not a normal directory,
in that it is never unrooted, and contains additional
structure that ordinary directories don't have (such as
multiple library attachments and alternate message and
command hash tables).
A directory is a data-class object so that execution of a
directory merely returns it to the stack. However, global
name execution has the property that executing the name of a
rooted (stored) directory makes that directory the current
directory rather than executing the directory itself.
The following words are available for directory
manipulation:
CONTEXT! ( rrp --> )
Stores a pointer to a rooted directory as the current directory
CONTEXT@ ( --> rrp )
Recalls the current context directory.
CREATEDIR ( id --> )
Creates a directory object in the current directory.
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DOVARS ( --> { id1 id2 ... } )
Returns list of variable names from the current directory.
HOMEDIR ( --> )
Makes HOME the current directory.
PATHDIR ( --> { HOME dir dir ... } )
Returns the current path.
UPDIR ( --> )
Switches context to the parent of the current directory.
XEQORDER ( { id1 id2 ... } --> )
ORDERs current directory.
XEQPGDIR ( id --> )
Purges a directory while respecting reference/garbage collection conventions.
19.3 The Hidden Directory
There is a hidden, nullnamed directory at the beginning of
the home directory, that contains the user key definitions
and alarm information. Application programs may use this
directory as well. However, remember that the user has no
way to detect or remove variables from this directory, so an
application should either remove such variables before
finishing, or to provide a command that lets the user remove
specific variables from the hidden directory.
These words provide store, recall and purge capabilities for
the hidden directory:
PuHiddenVar ( id --> ) Purges the hidden variable named id.
RclHiddenVar ( id --> ob TRUE )
( id --> FALSE )
Recalls (@) a hidden variable.
StoHiddenVar ( ob id --> )
Stores ob in hidden variable
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19.4 Additional Memory Utilities
GARBAGE ( --> )
Forces garbage collection.
MEM( --> # )
Returns the amount of free memory (a garbage collection is not forced)
OCRC ( ob --> #nibbles checksum(hxs) Returns size of object in nibbles and
a hex string checksum
getnibs ( hxsDATA hxsADDR --> hxsDATA' ) Internal RPL version of PEEK
putnibs ( hxsDATA hxsADDR --> ) Internal RPL version of POKE
Page 93
20. Display Management & Graphics
Most user RPL graphics commands are directed to the graphics
screen, which is the graphics object visible in the plot
environment. However, the "text screen," the grob visible in
the standard stack environment, has the same properties as
the graph screen, and should be used by application programs
for graphics displays whenever possible, to leave the graph
screen as a user "owned" resource. The EquationWriter does
this, for example, as does the HP82211A HP Solve Equation
Library card.
20.1 Display Organization
HP 48 system RAM contains three dedicated graphics objects
used for display purposes:
Pointer Grob Location
--------- ---------------- ---------
+--------------+
HARDBUFF2 -> | Menu labels | (Low Mem)
+--------------+
ABUFF -> | text grob |
+--------------+
GBUFF -> | graph grob | (Hi Mem)
+--------------+
The text grob and graph grob may be enlarged, and may be
scrolled.
The word TOADISP switches makes the text grob visible;
TOGDISP switches the LCD to the graph grob.
The following words are useful for returning display grobs
to the stack:
ABUFF ( --> textgrob )
GBUFF ( --> graphgrob )
HARDBUFF ( --> HBgrob )
Returns whichever of the text or graph grob is currently displayed.
HARDBUFF2 ( --> menugrob )
HBUFF_X_Y( --> HBgrob #x1 #y1 )
A ram pointer named VDISP indicates which grob is currently
shown in the display. VDISP may point to either the text
grob or the graph grob. VDISP is not directly accessible -
the word HARDBUFF returns the current display grob to the
stack (see below). Remember that ABUFF and GBUFF just
return pointers, so if the grob is being recalled for
modification and later return to the user, TOTEMPOB should
be used to create a unique copy in temporary memory.
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From a user's point of view, the text display is organized
into three regions, and the internal numbering convention
for these areas is reflected in many of the display control
words (see "Display Area Control" below). The display areas
are numbered 1, 2, and 3. The letters "DA", for "Display
Area", are found in the names of some display control words.
+-------------------+
DA1 | directory time | Status line (16 lines)
+-------------------+
|4: |
DA2a |3: | Stack
+-------------------+ Display
DA2b |2: | (40 lines total)
|1: |
+-------------------+
DA3 | 1 2 3 4 5 6 | Menu labels (8 lines)
+-------------------+
Display area 2 is actually divided into areas 2a and 2b, a
distinction most often used by the command line line. The
boundary between 2a and 2b can move, but the overall sizes
of areas 1, 2, and 3 are fixed.
20.2 Preparing the Display
Two words establish control over the text display. These
words are RECLAIMDISP and ClrDA1IsStat.
The word RECLAIMDISP performs the following actions:
+ Makes sure the text grob is the current display.
+ Clears the text display.
+ Resizes the text grob to the standard size (131 wide by
56 high) if necessary.
RECLAIMDISP is very much like the user word CLLCD, except
that CLLCD does not resize the text grob.
The word ClrDA1IsStat suspends the ticking clock display,
and is optional. If user input will be requested using words
like WaitForKey or a parameterized outer loop (see "Keyboard
Input"), then the clock updates will continue, and may botch
the display.
An example usage of ClrDA1IsStat can be found in the
Periodic Table application, where a user can enter a
molecular formula. The word WaitForKey is used to get
keystrokes, and ClrDA1IsStat prevents the clock from
overwriting the Periodic Table grid display.
If the menu display is not needed, the word TURNMENUOFF will
remove DA3 from the display and enlarge the text grob to be
Page 95
131x64. The corresponding word TURNMENUON restores the menu
display.
A simplified framework for an application secondary which
can be invoked by an end user and uses the text display
looks like this:
::
ClrDA1IsStat ( *Suspend clock display updates* )
RECLAIMDISP ( *Assert & clear alpha display* )
TURNMENUOFF ( *Remove menu keys* )
< application >
ClrDAsOK -\ ( *Tell the 48 to redraw the lcd* )
-or- > Choose one
SetDAsTemp -/ ( *Freeze all display areas* )
;
20.3 Controlling Display Refresh
When an application terminates or returns to the system
outer loop for keyboard input, several internal versions of
the user word FREEZE are available to control the display,
and there is a word that ensures that certain display or all
display areas will be redrawn:
SetDA1Temp Freeze display area 1
SetDA2aTemp Freeze display area 2a
SetDA2bTemp Freeze display area 2b
SetDA3Temp Freeze display area 3
SetDAsTemp Freeze all display areas
ClrDAsOK Redraw the entire lcd when program ends
There are still more variations on this theme - see the
chapter "Keyboard Input" for more.
Page 96
20.4 Clearing the Display
The following words may be used to clear either the whole
display or a portion of HARDBUFF. Remember that HARDBUFF
refers to the currently displayed grob, which is either the
text grob or the graph grob.
BLANKIT ( #startrow #rows --> )
Clears #rows starting at #startrow
BlankDA12 ( --> )
Clears rows 0 through 56
BlankDA2 ( --> )
Clears rows 16 through 56
CLEARVDISP ( --> )
Zeros out all of HARDBUFF
Clr16 ( --> )
Clears top 16 pixel rows
Clr8 ( --> )
Clears top 8 pixel rows
Clr8-15 ( --> )
Clears pixel rows 8-15
20.5 Annunciator Control
The following words control the left-shift, right-shift, and
alpha annunciators. It is unlikely that an application
should have to control these directly, and misuse of these
words can lead to misleading displays after an application
terminates.
ClrAlphaAnn Clears the alpha annunciator
ClrLeftAnn Clears the left-shift annunciator
ClrRightAnn Clears the right-shift annunciator
SetAlphaAnn Sets the alpha annunciator
SetLeftAnn Sets the left-shift annunciator
SetRightAnn Sets the right-shift annunciator
Page 97
20.6 Display Coordinates
The upper-left pixel of the display has the coordinates x=0
y=0, which are the same as user pixel coordinates { #0 #0 }.
The lower-right pixel coordinate is x=130 y=63.
NOTE: subgrobs are taken from the upper-left coordinate to
the pixel below and to the right of the lower right corner.
The terms #x1 and #y1 refer to the upperleft pixel of a sub
area, while #x2 and #y2 refer to the pixel below and the
right of the lower right corner.
{ #0 #0 } +------------------------------+
{#x1 #y1} |* |
| |
| GOR +----+ |
| coordinate|* | |
| | | |
| +----+ |
| * Subgrob |
| coordinate |
| |
| *| <- { #130 #63 }
+------------------------------+
* <- { #x2 #y2 }
20.6.1 Window_Coordinates
The following routines return HARDBUFF and coordinates for
portions of the display in a form suitable for a subsequent
call to SUBGROB. The terms #x1 and #y1 refer to the upper
left corner of the window on the currently displayed grob.
If the grob has been scrolled, these will NOT be #0 #0!
If HARDBUFF has been scrolled, some display words may not be
appropriate to use since they depend on the upper left
corner of the display being #0 #0. The LCD is then called
the "window", and the terms #x1 and #y1 will refer to the
pixel coordinates of the upper left corner of the window.
The word HBUFF_X_Y returns HARDBUFF and these window
coordinates. The word WINDOWCORNER returns just the window
coordinates. The words DISPROW1* and DISPROW2* mentioned
below work relative to the window corner.
Rows8-15 ( --> HBgrob #x1 #y1+8 #x1+131 #y1+16 )
TOP16 ( --> HBgrob #x1 #y1 #x1+131 #y1+16 )
TOP8 ( --> HBgrob #x1 #y1 #x1+131 #y1+8 )
WINDOWCORNER ( --> #x #y )
Returns pixel numbers of upperleft corner
of the window
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The word Save16 calls TOP16 and SUBGROB to produce a grob
consisting of the top 16 rows of the current display:
Save16 ( --> grob )
Equivalent words that save the top eight rows or rows 8-15
are not in the HP 48, but can be written as follows:
:: TOP8 SUBGROB ; ( --> grob ) ( *Saves the top 8 rows* )
:: TOP8-15 SUBGROB ; ( --> grob ) ( *Saves the top 8-15 rows* )
20.7 Displaying Text
There are three fonts available in the HP 48, distinguished
by size. The smallest font is variable width; the medium
and large fonts are fixed width.
The words described below display text using the medium and
large fonts in specific areas. Use of the small fonts, and
other placement options for the medium and large fonts must
be done in graphics, which is described later.
20.7.1 Standard_Text_Display_Areas
When the text grob is the current display AND has not been
scrolled, the following words may be used to display text in
the medium (5x7) font. Long strings are truncated to 22
characters with a trailing ellipsis (...), and strings
shorter than 22 characters are blank filled.
DISPROW1 ( $ --> )
DISPROW2 ( $ --> )
DISPROW3 ( $ --> )
DISPROW4 ( $ --> )
DISPROW5 ( $ --> )
DISPROW6 ( $ --> )
DISPROW7 ( $ --> )
DISPN ( $ #row --> )
DISP5x7 ( $ #start #max )
(0,0) (130,0)
DISPROW1 writes into +--------------------+
| |
+--------------------+
(0,7) (130,7)
(0,8) (130,8)
DISPROW2 writes into +--------------------+
| |
+--------------------+
(0,15) (130,15)
(etc.)
Page 99
The word DISP5x7 may be used to display a string that spans
more than one line of the display. The string must have
embedded carriage returns to show where to break to the next
display line. If a line segment is greater than 22
characters, it will be truncated and displayed with a
trailing ellipsis (...). The string is displayed starting
at row #start for #max rows.
The following words may be used to display text in the large
(5x9) font. Long strings are truncated to 22 characters
with a trailing ellipsis (...), and strings shorter than 22
characters are blank filled.
BIGDISPROW1 ( $ --> )
BIGDISPROW2 ( $ --> )
BIGDISPROW3 ( $ --> )
BIGDISPROW4 ( $ --> )
BIGDISPN ( $ #row --> )
(0,17) (130,0)
BIGDISPROW1 writes into +--------------------+
| |
+--------------------+
(0,26) (130,26)
(0,27) (130,27)
BIGDISPROW2 writes into +--------------------+
| |
+--------------------+
(0,36) (130,36)
(etc.)
Page 100
20.7.2 Temporary_Messages
Sometimes it is convenient to display a warning, then return
the display to its previous state. There are several
techniques and tools available for this. The easiest way to
do this is with the word FlashWarning. The code for
FlashWarning looks like this:
FlashWarning ( $ --> )
::
ERRBEEP ( *Generate an error beep* )
Save16 ( *Save the top 16 pixel rows* )
SWAP DISPSTATUS2 ( *Display the warning* )
VERYVERYSLOW ( *Wait about 3 seconds* )
Restore16 ( *Restore the top 16 rows* )
;
Variations on FlashWarning can be constructed using words
like TOP16 or a version suggested above that saves fewer
rows. The example below saves the top 8 rows and displays a
one line message for about .6 second:
::
TOP8 SUBGROB ( *Save the top 8 rows* )
SWAP DISPROW1* ( *Display the message* )
VERYSLOW VERYSLOW ( *Short delay* )
Restore8 ( *Restore the top 8 rows* )
;
NOTE: It is important to use DISPROW1* and DISPROW2* instead
of DISPROW1 and DISPROW2 if there is any chance that
HARDBUFF has been scrolled. There are no corresponding
words for other display lines.
Page 101
20.8 Graphics Objects
The following section presents tools for creating,
manipulating, and displaying graphics objects.
20.8.1 Warnings
Here are two warnings:
1. The term "bang-type operation" refers to an operation
performed directly upon an object without making a
copy. The naming convention for words which perform
this kind of operation often have an exclamation point
to denote a "bang" operation, such as GROB! or
GROB!ZERO.
You must remember two things when using "bang"
operations:
+ Since the object itself is modified, any pointers
on the stack that refer to that object will now
point to a changed object. The word CKREF may be
used to ensure that an object is unique.
+ These operations have no error checking, so
improper or out-of-range parameters may corrupt
memory beyond recovery.
2. In practice, it is best to use the word XYGROBDISP to
place a grob into the display grob. The word
XYGROBDISP is conservative in nature - if the graphic
to be placed in HARDBUFF would exceed the boundaries
of HARDBUFF, the HARDBUFF grob is enlarged to
accomodate the new grob.
Page 102
20.8.2 Graphics_Tools
The following words create or modify graphics objects:
$>BIGGROB ( $ --> grob ) ( 5x9 font )
$>GROB ( $ --> grob ) ( 5x7 font )
$>grob ( $ --> grob ) ( 3x7 font )
DOLCD> ( --> 64x131grob )
GROB! ( grob1 grob2 #col #row --> )
Stores grob1 into grob2. This is a
bang-type word with no error checks!
GROB!ZERO ( grob #x1 #y1 #x2 #y2 --> grob' )
Zeros out a rectangular section of a
grob. NOTE: Bang-type operation.
GROB!ZERODRP ( grob #x1 #y1 #x2 #y2 --> )
Zeros out a rectangular section of a
grob. NOTE: Bang-type operation!
GROB>GDISP ( grob --> )
Stores graph grob with new grob.
HARDBUFF ( --> HBgrob (the current display grob) )
HEIGHTENGROB ( grob #rows --> )
Adds #rows to grob, unless grob is null.
NOTE: Assumes text grob or graph grob!
INVGROB ( grob --> grob' )
Invert grob data bits - bang-type.
LINEOFF ( #x1 #y1 #x2 #y2 --> )
Clears pixels in a line in text grob
Note: #x2 must be > #x1 (use ORDERXY#)
LINEOFF3 ( #x1 #y1 #x2 #y2 --> )
Clears pixels in a line in graph grob
Note: #x2 must be > #x1 (use ORDERXY#)
LINEON ( #x1 #y1 #x2 #y2 --> )
Sets pixels in a line in text grob
Note: #x2 must be > #x1 (use ORDERXY#)
LINEON3 ( #x1 #y1 #x2 #y2 --> )
Sets pixels in a line in graph grob
Note: #x2 must be > #x1 (use ORDERXY#)
MAKEGROB ( #height #width --> grob )
ORDERXY# ( #x1 #y1 #x2 #y2 --> #x1 #y1 #x2 #y2 )
Orders two points for line drawing
PIXOFF ( #x #y --> )
Clears a pixel in the text grob
PIXOFF3 ( #x #y --> )
Clears a pixel in the graph grob
PIXON ( #x #y --> )
Sets a pixel in the text grob
PIXON? ( #x #y --> flag )
Returns TRUE if text grob pixel is set
PIXON?3 ( #x #y --> flag )
Returns TRUE if graph grob pixel is set
PIXON3 ( #x #y --> )
Sets a pixel in the graph grob
SUBGROB ( grob #x1 #y1 #x2 #y2 --> subgrob )
Symb>HBuff ( symb --> )
Displays symb in HARDBUFF in Equation-
Writer form. May enlarge HARDBUFF, so
do RECLAIMDISP afterwards.
Page 103
TOGLINE ( #x1 #y1 #x2 #y2 --> )
Toggles pixels in a line in text grob
TOGLINE3 ( #x1 #y1 #x2 #y2 --> )
Toggles pixels in a line in graph grob
NOTE: #x2 must be greater than #x1 for line drawing!
20.8.3 Grob_Dimensions
The following words return or verify size information:
CKGROBFITS ( grob1 grob2 #n #m --> grob1 grob2' #n #m )
Truncates grob2 if it doesn't fit in grob1
DUPGROBDIM ( grob --> grob #height #width )
GBUFFGROBDIM ( --> #height #width )
Returns dimensions of graph grob
GROBDIM ( grob --> #height #width )
GROBDIMw ( grob --> #width )
20.8.4 Built-in_Grobs
The following words refer to built-in grobs:
BigCursor 5x9 Cursor (outline box)
CROSSGROB 5x5 "+" symbol
CURSOR1 5x9 Insert Cursor (arrow)
CURSOR2 5x9 Replace Cursor (solid box)
MARKGROB 5x5 "X" symbol
MediumCursor 5x7 Cursor (outline box)
SmallCursor 3x5 Cursor (outline box)
Page 104
20.8.5 Menu_Display_Utilities
Menu labels are grobs which are 8 rows high and 21 pixels
wide. The columns for menu key labels in HARDBUFF2 are:
ZERO Softkey 1
TWENTYTWO Softkey 2
# 0002C Softkey 3
# 00042 Softkey 4
# 00058 Softkey 5
# 0006E Softkey 6
The routine DispMenu.1 redisplays the current menu; the
routine DispMenu redisplays the current menu and also calls
SetDA3Valid to "freeze" the menu display line.
The following words convert objects to menu labels and
display the labels at the given column number:
Grob>Menu ( #col 8x21grob --> )
Displays an 8x21 (only!) grob
Id>Menu ( #col Id --> )
Recalls Id and displays standard label
or directory label, depending on the
contents of Id.
Seco>Menu ( #col seco --> )
Evaluates secondary and uses result to
produce and display appropriate menu label
Str>Menu ( #col $ --> )
Makes and displays standard menu label
The following words convert strings to the different kinds
of available menu key grobs:
MakeBoxLabel ( $ --> grob ) Box with bullet in it
MakeDirLabel ( $ --> grob ) Box with directory bar
MakeInvLabel ( $ --> grob ) White label (solver)
MakeStdLabel ( $ --> grob ) Black label (standard)
20.9 Scrolling the Display
The following words are available for scrolling the display:
SCROLLDOWN ( *Scroll down one pixel with repeat* )
SCROLLLEFT ( *Scroll left one pixel with repeat* )
SCROLLRIGHT ( *Scroll right one pixel with repeat* )
SCROLLUP ( *Scroll up one pixel with repeat* )
JUMPBOT ( *Move window to bottom edge of grob* )
JUMPLEFT ( *Move window to left edge of grob* )
JUMPRIGHT ( *Move window to right edge of grob* )
JUMPTOP ( *Move window to bottom edge of grob* )
The SCROLL* words test to see if their corresponding arrow
key is being held down, and repeat their action until the
Page 105
edge of the grob is reached or the key released.
The example below illustrates a series of graphics
operations and the use of a Parameterized Outer Loop which
provides scrolling for the user.
*---------------------------------------------------------
*
* Include the header file KEYDEFS.H, which defines words
* like kcUpArrow at physical key numbers.
*
INCLUDE KEYDEFS.H
*
* Include the eight characters needed for binary download
*
ASSEMBLE
NIBASC /HPHP48-D/
RPL
*
* Begin the secondary
*
::
RECLAIMDISP ( *Claim the alpha display* )
ClrDA1IsStat ( *Temporarily disable clock* )
* ( *Try removing ClrDA1IsStat* )
ZEROZERO ( #0 #0 )
150 150 MAKEGROB ( #0 #0 150x150grob )
XYGROBDISP ( )
TURNMENUOFF ( *Turn off menu line* )
*
* Draw diagonal lines. Remember that LINEON requires
* requires #x2>#x1!
*
ZEROZERO ( #x1 #y1 )
149 149 ( #x1 #y1 #x2 #y2 )
LINEON ( *Draw line* )
ZERO 149 ( #x1 #y1 )
149 ZERO ( #x1 #y1 #x2 #y2 )
LINEON ( *Draw line* )
*
* Place text
*
HARDBUFF
75 50 "SCROLLING" ( HBgrob 75 150 "SCROLLING" )
150 CENTER$3x5 ( HBgrob )
75 100 "EXAMPLE" ( HBgrob 75 100 "EXAMPLE" )
150 CENTER$3x5 ( HBgrob )
DROPFALSE ( FALSE )
{ LAM Exit } BIND ( *Bind POL exit flag* )
' NOP ( *No display action* )
' :: ( *Hard key handler* )
kpNoShift #=casedrop
::
kcUpArrow ?CaseKeyDef
:: TakeOver SCROLLUP ;
Page 106
kcLeftArrow ?CaseKeyDef
:: TakeOver SCROLLLEFT ;
kcDownArrow ?CaseKeyDef
:: TakeOver SCROLLDOWN ;
kcRightArrow ?CaseKeyDef
:: TakeOver SCROLLRIGHT ;
kcOn ?CaseKeyDef
:: TakeOver
TRUE ' LAM Exit STO ;
kcRightShift #=casedrpfls
DROP 'DoBadKeyT
;
kpRightShift #=casedrop
::
kcUpArrow ?CaseKeyDef
:: TakeOver JUMPTOP ;
kcLeftArrow ?CaseKeyDef
:: TakeOver JUMPLEFT ;
kcDownArrow ?CaseKeyDef
:: TakeOver JUMPBOT ;
kcRightArrow ?CaseKeyDef
:: TakeOver JUMPRIGHT ;
kcRightShift #=casedrpfls
DROP 'DoBadKeyT
;
2DROP 'DoBadKeyT
;
TrueTrue ( *Key control flags* )
NULL{} ( *No softkeys here* )
ONEFALSE ( *1st row, no suspend* )
' LAM Exit ( *App exit condition* )
' ERRJMP ( *Error handler* )
ParOuterLoop ( *Run the ParOuterLoop* )
TURNMENUON ( *Restore menu row* )
RECLAIMDISP ( *Resize and clear display* )
;
Page 107
The above code, if stored in a file SCROLL.S, can be
compiled as follows:
RPLCOMPILE SCROLL.S
SASM SCROLL.A
SLOAD -H SCROLL.M
This example also assumes that the file KEYDEFS.H is either
in the same directory or the source file has been modified
to reflect the location of KEYDEFS.H. The loader control
file SCROLL.M looks like this:
OU SCROLL
LL SCROLL.LR
SU XR
SE ENTRIES.O
RE SCROLL.O
The final file, SCROLL, may be binary downloaded to the
HP 48 for a test.
When SCROLL is running, the arrow keys scroll the display,
and the right-shifted arrow keys move the window to the
corresponding boundary. The [ATTN] key terminates the
program.
For more details on the ParOuterLoop, see the chapter
"Keyboard Control".
Page 108
21. Keyboard Control
A program that requires keyboard input from the user may
choose from three basic techniques available with internal
RPL, listed in order of increasing complexity:
1. Wait for an individual keystroke, then decide what to
do with it.
2. Call the internal form of INPUT.
3. Set up a Parameterized Outer Loop to control an entire
application environment.
The following sections discuss the internal numbering scheme
for keys and each of the above three key processing
strategies.
21.1 Key Locations
The user word WAIT returns a real number which is encoded in
the form rc.p, where:
r = The row of the key
c = The column of the key
p = The shift plane.
+--------+----------------+---+---------------------+
| p | Primary Planes | p | Alpha Planes |
+--------+----------------+---+---------------------+
| 0 or 1 | Unshifted | 4 | Alpha |
| 2 | Left-shifted | 5 | Alpha left-shifted |
| 3 | Right-shifted | 6 | Alpha right-shifted |
+--------+----------------+---+---------------------+
Internally, key locations are represented with two binary
integers: #KeyCode, which defines a physical key, and
#Plane, which defines the shift plane.
The file KEYDEFS.H, supplied with the RPL compiler, defines
the following terms for key planes:
DEFINE kpNoShift ONE
DEFINE kpLeftShift TWO
DEFINE kpRightShift THREE
DEFINE kpANoShift FOUR
DEFINE kpALeftShift FIVE
DEFINE kpARightShft SIX
Page 109
Keys are numbered internally from 1 to 49, starting at the
upper left corner of the keyboard. Primary key definitions
are also provided in KEYDEFS.H. Here are a few of them:
DEFINE kcMenuKey1 ONE
DEFINE kcMenuKey2 TWO
DEFINE kcMenuKey3 THREE
DEFINE kcMenuKey4 FOUR
DEFINE kcMenuKey5 FIVE
DEFINE kcMenuKey6 SIX
DEFINE kcMathMenu SEVEN
DEFINE kcPrgmMenu EIGHT
DEFINE kcCustomMenu NINE
...
DEFINE KcPlus FORTYNINE
The use of these definitions in source code is encouraged
for legibility.
The translation between internal key numbering and rc.p
numbering may be carried out with two words:
Ck&DecKeyLoc ( %rc.p --> #KeyCode #Plane )
CodePl>%rc.p ( #KeyCode #Plane --> %rc.p )
21.2 Waiting for a Key
If an application needs to wait for a single key, such as a
yes-no-attn type decision, it is best to use the word
WaitForKey, which returns a fully formed keystroke.
WaitForKey also keeps the HP 48 in a low-power state until a
key is pressed and handles the alpha and shift annunciators
and alarm processing.
The following words are available:
CHECKKEY ( --> #KeyCode TRUE )
( --> FALSE )
Returns, but does not pop, the next
key in the buffer.
FLUSHKEYS ( --> )
Flush the key buffer.
GETTOUCH ( --> #KeyCode TRUE )
( --> FALSE )
Pops next key from buffer.
KEYINBUFFER? ( --> FLAG )
Returns TRUE if a key is in the buffer,
otherwise returns FALSE.
ATTN? ( --> flag )
Returns TRUE if [ATTN] has been pressed
ATTNFLGCLR ( --> )
Clears the attn key flag (does not
flush attn key from buffer)
WaitForKey ( --> #KeyCode #Plane )
Returns next fully formed keystroke.
Page 110
21.3 InputLine
The word InputLine is the core of the user word INPUT as
well as the prompt for equation names (NEW). InputLine does
the following:
+ Displays the prompt in display area 2a,
+ Sets the keyboard entry modes,
+ Initializes the edit line,
+ Accepts user input until [ENTER] is either explicitly or
implicitly pressed,
+ Parses, evaluates, or just returns the user-input edit
line,
+ Returns TRUE if exited by Enter or FALSE if aborted by
Attn.
The stack on entry must contain the following:
$Prompt The prompt to be displayed during user input
$EditLine The initial edit line
CursorPos The initial edit line cursor position, specified
as a binary integer character number or a two-
element list of binary integer row and column
numbers. For all numbers, #0 indicates the end
of the edit line, row, or column.
#Ins/Rep The initial insert/replace mode:
#0 current insert/replace mode
#1 insert mode
#2 replace mode
#Entry The initial entry mode:
#0 current entry mode plus program entry
#1 program/immediate entry
#2 program/algebraic entry
#AlphaLock The initial alpha-lock mode:
#0 current alpha lock mode
#1 alpha lock enabled
#2 alpha lock disabled
ILMenu The initial InputLine menu in the format
specified by "ParOuterLoop"
#ILMenuRow The initial InputLine menu row number in the
format specified by "ParOuterLoop"
AttnAbort? A flag specifying whether pressing Attn while
a non-null edit line exists should abort
"InputLine" (TRUE) or just clear the edit
line (FALSE)
#Parse How to process the resulting edit line:
#0 Return the edit line as a string
#1 Return the edit line as a string AND
as a parsed object
#2 Parse and evaluate the edit line
Page 111
InputLine returns different results, depending on the
initial value of #Parse:
#Parse Stack Description
------ ----------------- ------------------------------
#0 $EditLine TRUE Edit line
#1 $EditLine ob TRUE Edit line and parsed edit line
#2 Ob1 ... Obn TRUE Resulting object or objects
FALSE Attn pressed to abort edit
21.3.1 InputLine_Example
The example call to InputLine shown below prompts the user
for a variable name. If the user enters a valid name, the
name and TRUE are returned, otherwise FALSE is returned.
( --> Ob TRUE | FALSE )
::
"Enter name:" ( *Prompt string* )
NULL$ ( *No default name* )
ONEONE ( *Initial edit line & cursor pos* )
ONEONE ( *Insert mode & prog/immed. entry* )
NULL{} ( *No edit menu* )
ONE ( *Menu row* )
FALSE ( *Attn clears edit line* )
ONE ( *Return edit line and parsed ob* )
InputLine ( ($editline ob TRUE) | (FALSE) )
NOTcaseFALSE ( *Exit if Attn pressed* )
SWAP NULL$? ( *Exit if blank edit line* )
casedrop FALSE
DUPTYPEIDNT? ( *Check if ob is id* )
caseTRUE ( *Yes, exit true* )
DROPFALSE ( *No, drop ob and FALSE* )
;
Page 112
21.4 The Parameterized Outer Loop
In this section, the term "parameterized outer loop" is used
to refer to a usage of the RPL word "ParOuterLoop", or a
combined usage of its fundamental component utilities
(described below), all of which can be envisioned as words
that take over the keyboard and display until a specified
condition is met.
The parameterized outer loop, "ParOuterLoop", takes nine
arguments, in order:
AppDisplay The display update object to be evaluated
before each key evaluation. "AppDisplay"
should handle display updating not handled by
the keys themselves, and should also perform
special handling of errors.
AppKeys The hard key assignments, a secondary object in
the format described below.
NonAppKeyOK? A flag specifying whether the hard keys not
assigned by the application should perform
their default actions or be canceled.
DoStdKeys? A flag used in conjunction with "NonAppKeyOK?"
specifying whether standard key definitions are
to be used for non-application keys instead of
default key processing.
AppMenu The menu key specification, a secondary or list
in the format specified in the menu key
assignments document, or FALSE.
#AppMenuRow The initial application menu row number. For
most applications, this should be binary
integer one.
SuspendOK? A flag specifying whether or not any user
command that would create a suspended
environment and restart the system outer loop
should instead generate an error.
ExitCond An object that evaluates to TRUE when the outer
loop is to be exited, or FALSE otherwise.
"ExitCond" is evaluated before each application
display update and key evaluation.
AppError The error-handling object to be evaluated if an
error occurs during the key evaluation part of
the parameterized outer loop.
The parameterized outer loop itself returns no results.
However, any of the keys used by the application can return
results to the data stack or in any manner desired.
Page 113
21.4.1 The_Parameterized_Outer_Loop_Utilities
The parameterized outer loop word "ParOuterLoop" consists
entirely of calls (with proper error handling) to its four
RPL utility words, in order:
POLSaveUI Saves the current user interface in a temporary
environment. Takes no arguments and returns no
results.
POLSetUI Sets the current user interface according to
the same parameters required by "ParOuterLoop".
Returns no results.
POLKeyUI Displays, reads and evaluates keys, handles
errors, and exits according to the user
interface specified by "POLSetUI". Takes no
arguments and returns no results.
POLRestoreUI Restores the user interface saved by
"POLSaveUI" and abandons the temporary
environment. Takes no arguments and returns no
results.
(In addition to the four utilities above. utility
"POLResUI&Err" is used to protect the saved user interface
in the event of an error that's not handled within the
parameterized outer loop. Refer to "Parameterized Outer
Loop Operation" and "Handling Errors with the Utilities",
below.)
These utilities can be used by applications that require
greater control over the user interface. For example:
+ For optimum performance an application can create a
temporary environment with null-named temporary
variables after calling "POLSaveUI", then access the
null-named variables "within" "POLKeyUI", since only
"POLSaveUI" creates a parameterized outer loop
temporary environment and only "POLRestoreUI" accesses
the same environment.
+ To avoid unnecessary and time-consuming overhead, an
application that uses multiple consecutive (not nested)
parameterized outer loops can call "POLSaveUI" at the
start of the application, then call "POLSetUI" and
"POLKeyUI" multiple times throughout the application,
then finally call "POLRestoreUI" at the end of the
application.
Page 114
21.4.2 Overview_of_the_Parameterized_Outer_Loop
The parameterized outer loop operates as outlined below.
("POLSaveUI")
Save the system or current application's
user interface
If error in
("POLSetUI")
Set the new application's user interface
("POLKeyUI")
While "ExitCond" evaluates to FALSE {
Evaluate "AppDisplay"
If error in
Read and evaluate a key
Then
Evaluate "AppError"
}
Then
Restore the saved user interface and
ERRJMP
("POLRestoreUI")
Restore the saved user interface
The parameterized outer loop creates one temporary
environment when it saves the current user interface, and it
abandons this environment when it restores a saved user
interface. This means that words that operate on the
topmost temporary environment, such as "1GETLAM", should NOT
be used "within" the parameterized outer loop (e.g., in a
key definition or the application display update object)
UNLESS the desired temporary environment is created AFTER
calling "POLSaveUI" and abandoned before calling
"POLRestoreUI". For temporary environments created before
calling the parameterized outer loop, applications should
set up and operate on NAMED temporary variables.
Page 115
21.4.3 Handling_Errors_with_the_Utilities
To insure that it can properly restore a saved user
interface if an error occurs within an application, the
parameterized outer loop protects the saved user interface
by setting an error trap immediately after its call to
"POLSaveUI", as shown below:
::
POLSaveUI ( save the current user interface )
ERRSET ( prepare to restore saved user interface
in case of error )
::
POLSetUI ( set the application's user interface )
POLKeyUI ( display, read, and evaluate )
;
ERRTRAP ( if error, then restore the saved
user interface and error )
POLResUI&Err
POLRestoreUI ( restore the saved user interface )
;
The purpose of supported utility "POLResUI&Err" is to
restore the user interface saved by "POLSaveUI" and then to
error.
Any applications that use the parameterized outer loop
utilities instead of "ParOuterLoop" are REQUIRED to include
this same level of error handling protection of the saved
user interface.
21.4.4 The_Display
There is no default display in the parameterized outer loop;
the application is responsible for setting up the initial
display and updating it.
There are two ways that an application can update the
display: with outer loop parameter "AppDisplay" or with key
assignments. For example, if the user presses the right-
arrow key to move a highlight from one matrix column to
another, the key assignment for the right-arrow key can
either pass information to "AppDisplay" (often implicitly)
to handle the change, or the key assignment object can
change the display itself. Both methods have advantages
under different circumstances.
Page 116
21.4.5 Error_Handling
The error-handling outer loop parameter "AppError" is
responsible for processing any errors generated during key
evaluation within the parameterized outer loop. If an error
occurs, "AppError" is evaluated. "AppError" should
determine the specific error and act accordingly. If an
application can not handle any errors, then "AppError"
should be specified as "ERRJMP".
21.4.6 Hard_Key_Assignments
Any HP 48 key, in any of the six planes (unshifted, left-
shifted, right-shifted, alpha-unshifted, alpha-left-shifted,
and alpha-right-shifted) can be assigned for the duration of
the parameterized outer loop. The outer loop parameter
"AppKeys" specifies the keys to assign and their new
assignments.
If a key is not assigned by an application, and outer loop
parameter "NonAppKeyOK?" is TRUE, then standard or default
key processing occurs, according to outer loop parameter
"DoStdKeys?". For example, if user keys mode is on and the
key has a user key assignment, then the user key is
processed if "DoStdKeys?" is FALSE, or the standard key is
processed if "DoStdKeys?" is TRUE. If "NonAppKeyOK?" is
FALSE, then all non-application keys issue a canceled key
warning beep and do nothing else.
In general, NonAppKeyOK? should be FALSE to maintain total
control.
Page 117
Application key assignments are specified by the secondary
object "AppKeys" passed to the parameterized outer loop.
The procedure must take as its arguments a key code and a
plane specification, and must return the desired key
definition and TRUE if the application defines the key, or
FALSE if the application doesn't. Specifically, the key
assignment procedure's stack diagram must look like this:
( #KeyCode #Plane --> KeyDef TRUE )
( #KeyCode #Plane --> FALSE )
The key definition result "KeyDef" will be processed by the
main key handler, "DoKeyOb".
Application key assignments specified as procedures
generally have logic in the form
If #Plane is NoShift (or first plane of interest)
Then
Process #KeyCode in the unshifted plane
Else
If #Plane is LeftShift (or next plane of interest)
Then
Process #KeyCode in the left-shifted plane
...
Else signal no definition
This can be implemented in RPL in the form
kpNoShift #=casedrop :: (process noshift plane) ;
kpLeftShift #=casedrop :: (process l-shift plane) ;
2DROP FALSE
Each plane handler generally has logic in the form
If #KeyCode is 7 (or first key code of interest)
Then
Return the key code 7 definition and TRUE
Else
If #KeyCode is 20 (or next key code of interest)
Then
Return the key code 20 definition and TRUE
Else signal no definition
This can be implemented in RPL in the following form:
kcMathMenu ?CaseKeyDef :: TakeOver (process MTH) ;
kcTan ?CaseKeyDef :: TakeOver (process TAN) ;
( all other keys )
DROP FALSE
Page 118
In order to save code and to make key definitions more
readable, the control structure word "?CaseKeyDef" replaces
the
#=casedrop :: ' <KeyDef> TRUE ;
portions of code with
?CaseKeyDef <KeyDef>
More specifically, "?CaseKeyDef" is used in the form
... #KeyCode #TestKeyCode ?CaseKeyDef <KeyDef> ...
If "#KeyCode" equals "#TestKeyCode", then "?CaseKeyDef"
drops "#KeyCode" and "#TestKeyCode", pushes "KeyDef" and
TRUE, and exits the calling secondary. Otherwise,
"?CaseKeyDef" drops "#TestKeyCode" only, skips "KeyDef", and
continues.
21.4.7 Menu_Key_Assignments
An application can specify any initial menu key assignments,
in any of three planes (unshifted, left-shifted, and right-
shifted), to be initialized when the parameterized outer
loop is started. The outer loop parameter "AppMenu"
specifies the initialization object (a list or secondary)
for the application's menu, or FALSE, indicating that the
current menu is to be left intact. When the parameterized
outer loop is exited, the previous menu is restored
automatically.
If "AppMenu" is a null list, then a set of six null menu key
assignments are made. If "AppMenu" is FALSE, then the menu
present when the parameterized outer loop is called is
maintained.
NOTE: hard key assignments have priority over menu key
assignments. This means that the hard key handler must
include the following line if menu keys are to be processed:
DUP#<7 casedrpfls
The parameter AppMenu takes the following form:
{
Menu Key 1 Definition
Menu Key 2 Definition
...
Menu Key n Definition
}
Where each menu key definition takes one of three
following forms:
Page 119
NullMenuKey
{ LabelObj :: TakeOver (Action) ; }
{ LabelObj {
:: TakeOver (Primary Action) ;
:: TakeOver (LeftShifted Action) ;
}
{ LabelObj {
:: TakeOver (Primary Action) ;
:: TakeOver (LfShifted Action) ;
:: TakeOver (RtShifted Action) ;
}
}
A LabelObj may be any object, but is usually a string or an
8x21 grob. See the example below for an illustration of
softkey use. The word NullMenuKey inserts a blank menu key
which just beeps when pressed.
21.4.8 Preventing_Suspended_Environments
An application may need to allow arbitrary commands and user
objects to be evaluated, but don't want the current
environment to be suspended by the "HALT" or "PROMPT"
commands. If the outer loop parameter "SuspendOK?" is
FALSE, then any command that would suspend the environment
generates a "HALT not Allowed" error, allowing "AppError" to
handle it. If "SuspendOK?" is TRUE, then the application
must be prepared to handle the consequences. The dangers
here are many and severe.
For all foreseeable applications, "SuspendOK?" should be
FALSE.
21.4.9 Specifying_an_Exit_Condition
The outer loop parameter "ExitCond" is an object that
evaluates to TRUE when the outer loop is to exited, or FALSE
otherwise. "ExitCond" is evaluated before each key
evaluation.
Page 120
21.4.10 ParOuterLoop_Example
*---------------------------------------------------------
*
* Include the header file KEYDEFS.H, which defines words
* like kcUpArrow at physical key numbers.
*
INCLUDE KEYDEFS.H
*
* Include the eight characters needed for binary download
*
ASSEMBLE
NIBASC /HPHP48-D/
RPL
*
* Begin the secondary
*
::
RECLAIMDISP ( *Claim the alpha display* )
ClrDA1IsStat ( *Temporarily disable clock* )
* ( *Try removing ClrDA1IsStat* )
ZEROZERO ( #0 #0 )
150 150 MAKEGROB ( #0 #0 150x150grob )
XYGROBDISP ( )
*
* Draw diagonal lines. Remember that LINEON requires
* requires #x2>#x1!
*
ZEROZERO ( #x1 #y1 )
149 149 ( #x1 #y1 #x2 #y2 )
LINEON ( *Draw line* )
ZERO 149 ( #x1 #y1 )
149 ZERO ( #x1 #y1 #x2 #y2 )
LINEON ( *Draw line* )
*
* Place text
*
HARDBUFF
75 50 "SCROLLING" ( HBgrob 75 150 "SCROLLING" )
150 CENTER$3x5 ( HBgrob )
75 100 "EXAMPLE" ( HBgrob 75 100 "EXAMPLE" )
150 CENTER$3x5 ( HBgrob )
DROPFALSE ( FALSE )
{ LAM Exit } BIND ( *Bind POL exit flag* )
' DispMenu.1 ( *Display Action shows menu* )
' :: ( *Hard key handler* )
kpNoShift #=casedrop
::
DUP#<7 casedrpfls ( *Enable softkeys* )
kcUpArrow ?CaseKeyDef
:: TakeOver SCROLLUP ;
kcLeftArrow ?CaseKeyDef
:: TakeOver SCROLLLEFT ;
kcDownArrow ?CaseKeyDef
:: TakeOver SCROLLDOWN ;
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kcRightArrow ?CaseKeyDef
:: TakeOver SCROLLRIGHT ;
kcOn ?CaseKeyDef
:: TakeOver
TRUE ' LAM Exit STO ;
kcRightShift #=casedrpfls
DROP 'DoBadKeyT
;
2DROP 'DoBadKeyT
;
TrueTrue ( *Key control flags* )
{
{ "TOP" :: TakeOver JUMPTOP ; }
{ "BOT" :: TakeOver JUMPBOT ; }
{ "LEFT" :: TakeOver JUMPLEFT ; }
{ "RIGHT" :: TakeOver JUMPRIGHT ; }
NullMenuKey
{ "QUIT" :: TakeOver TRUE ' LAM Exit STO ; }
}
ONEFALSE ( *1st row, no suspend* )
' LAM Exit ( *App exit condition* )
' ERRJMP ( *Error handler* )
ParOuterLoop ( *Run the ParOuterLoop* )
RECLAIMDISP ( *Resize and clear display* )
SetDAsBAD ( *Redraw display* )
;
The above code, if stored in a file SCRSFKY.S, can be
compiled as follows:
RPLCOMPILE SCRSFKY.S
SASM SCRSFKY.A
SLOAD -H SCRSFKY.M
This example also assumes that the file KEYDEFS.H is either
in the same directory or the source file has been modified
to reflect the location of KEYDEFS.H. The loader control
file SCRSFKY.M looks like this:
OU SCRSFKY
LL SCRSFKY.LR
SU XR
SE ENTRIES.O
RE SCRSFKY.O
The final file, SCRSFKY, may be binary downloaded to the
HP 48 for a test.
When SCRSFKY is running, the arrow keys scroll the display,
and the labeled softkeys move the window to the
corresponding boundary. The [ATTN] key terminates the
program.
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22. System Commands
The following words set, test, or control various system
conditions or modes.
ALARM? ( --> flag )
Returns TRUE if an alarm is due
AtUserStack ( --> )
Declares user ownership of all objects
on the stack.
CLKTICKS ( --> hxs )
Returns 13 nibble hex string reflecting
the number of ticks since 01/01/0000.
There are 8192 ticks per second.
ClrSysFlag ( # --> )
Clears system flag from #1 to #64
ClrUserFlag ( # --> )
Clears user flag from #1 to #64
DATE ( --> %date )
Returns real number date
DOBEEP ( %freq %duration --> )
BEEP command
DOBIN ( --> )
Set base mode to BINary
DODEC ( --> )
Set base mode to DECimal
DOENG ( # --> )
Set ENG display with # (0-11) digits
DOFIX ( # --> )
Set FIX display with # (0-11) digits
DOHEX ( --> )
Set base mode to HEXadecimal
DOOCT ( --> )
Set base mode to OCTal
DOSCI ( # --> )
Set SCI display with # (0-11) digits
DOSTD ( --> )
Set STD display mode
DPRADIX? ( --> flag )
Returns TRUE if current radix is .
Returns FALSE if current radix is ,
SETDEG ( --> )
Set DEGREES angle mode
SETGRAD ( --> )
Set GRADS angle mode
SETRAD ( --> )
Set RADIANS angle mode
SLOW ( --> )
15msec delay
TOD ( --> %time )
Returns time of day in h.ms form
TestSysFlag ( # --> flag )
Returns TRUE if system flag # is set
TestUserFlag ( # --> flag )
Returns TRUE if user flag # is set
VERYSLOW ( --> )
300 msec delay
VERYVERYSLOW ( --> )
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3 sec delay
WORDSIZE ( --> # )
Returns binary wordsize
dostws ( # --> )
Stores binary wordsize
dowait ( %seconds --> )
Waits for %seconds in light sleep
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