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This is Info file ../../info/lispref.info, produced by Makeinfo version 1.68 from the input file lispref.texi. Edition History: GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp Programmer's Manual (for 19.13) Third Edition, July 1995 XEmacs Lisp Reference Manual (for 19.14 and 20.0) v3.1, March 1996 XEmacs Lisp Reference Manual (for 19.15 and 20.1, 20.2) v3.2, April, May 1997 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc. Copyright (C) 1995, 1996 Ben Wing. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English. File: lispref.info, Node: Basic Coding System Functions, Next: Coding System Property Functions, Prev: Coding System Properties, Up: Coding Systems Basic Coding System Functions ----------------------------- - Function: find-coding-system CODING-SYSTEM-OR-NAME This function retrieves the coding system of the given name. If CODING-SYSTEM-OR-NAME is a coding-system object, it is simply returned. Otherwise, CODING-SYSTEM-OR-NAME should be a symbol. If there is no such coding system, `nil' is returned. Otherwise the associated coding system object is returned. - Function: get-coding-system NAME This function retrieves the coding system of the given name. Same as `find-coding-system' except an error is signalled if there is no such coding system instead of returning `nil'. - Function: coding-system-list This function returns a list of the names of all defined coding systems. - Function: coding-system-name CODING-SYSTEM This function returns the name of the given coding system. - Function: make-coding-system NAME TYPE &optional DOC-STRING PROPS This function registers symbol NAME as a coding system. TYPE describes the conversion method used and should be one of the types listed in *Note Coding System Types::. DOC-STRING is a string describing the coding system. PROPS is a property list, describing the specific nature of the character set. Recognized properties are as in *Note Coding System Properties::. - Function: copy-coding-system OLD-CODING-SYSTEM NEW-NAME This function copies OLD-CODING-SYSTEM to NEW-NAME. If NEW-NAME does not name an existing coding system, a new one will be created. - Function: subsidiary-coding-system CODING-SYSTEM EOL-TYPE This function returns the subsidiary coding system of CODING-SYSTEM with eol type EOL-TYPE. File: lispref.info, Node: Coding System Property Functions, Next: Encoding and Decoding Text, Prev: Basic Coding System Functions, Up: Coding Systems Coding System Property Functions -------------------------------- - Function: coding-system-doc-string CODING-SYSTEM This function returns the doc string for CODING-SYSTEM. - Function: coding-system-type CODING-SYSTEM This function returns the type of CODING-SYSTEM. - Function: coding-system-property CODING-SYSTEM PROP This function returns the PROP property of CODING-SYSTEM. File: lispref.info, Node: Encoding and Decoding Text, Next: Detection of Textual Encoding, Prev: Coding System Property Functions, Up: Coding Systems Encoding and Decoding Text -------------------------- - Function: decode-coding-region START END CODING-SYSTEM &optional BUFFER This function decodes the text between START and END which is encoded in CODING-SYSTEM. This is useful if you've read in encoded text from a file without decoding it (e.g. you read in a JIS-formatted file but used the `binary' or `no-conversion' coding system, so that it shows up as `^[$B!<!+^[(B'). The length of the encoded text is returned. BUFFER defaults to the current buffer if unspecified. - Function: encode-coding-region START END CODING-SYSTEM &optional BUFFER This function encodes the text between START and END using CODING-SYSTEM. This will, for example, convert Japanese characters into stuff such as `^[$B!<!+^[(B' if you use the JIS encoding. The length of the encoded text is returned. BUFFER defaults to the current buffer if unspecified. File: lispref.info, Node: Detection of Textual Encoding, Next: Big5 and Shift-JIS Functions, Prev: Encoding and Decoding Text, Up: Coding Systems Detection of Textual Encoding ----------------------------- - Function: coding-category-list This function returns a list of all recognized coding categories. - Function: set-coding-priority-list LIST This function changes the priority order of the coding categories. LIST should be a list of coding categories, in descending order of priority. Unspecified coding categories will be lower in priority than all specified ones, in the same relative order they were in previously. - Function: coding-priority-list This function returns a list of coding categories in descending order of priority. - Function: set-coding-category-system CODING-CATEGORY CODING-SYSTEM This function changes the coding system associated with a coding category. - Function: coding-category-system CODING-CATEGORY This function returns the coding system associated with a coding category. - Function: detect-coding-region START END &optional BUFFER This function detects coding system of the text in the region between START and END. Returned value is a list of possible coding systems ordered by priority. If only ASCII characters are found, it returns `autodetect' or one of its subsidiary coding systems according to a detected end-of-line type. Optional arg BUFFER defaults to the current buffer. File: lispref.info, Node: Big5 and Shift-JIS Functions, Prev: Detection of Textual Encoding, Up: Coding Systems Big5 and Shift-JIS Functions ---------------------------- These are special functions for working with the non-standard Shift-JIS and Big5 encodings. - Function: decode-shift-jis-char CODE This function decodes a JISX0208 character of Shift-JIS coding-system. CODE is the character code in Shift-JIS as a cons of type bytes. The corresponding character is returned. - Function: encode-shift-jis-char CH This function encodes a JISX0208 character CH to SHIFT-JIS coding-system. The corresponding character code in SHIFT-JIS is returned as a cons of two bytes. - Function: decode-big5-char CODE This function decodes a Big5 character CODE of BIG5 coding-system. CODE is the character code in BIG5. The corresponding character is returned. - Function: encode-big5-char CH This function encodes the Big5 character CHAR to BIG5 coding-system. The corresponding character code in Big5 is returned. File: lispref.info, Node: CCL, Next: Category Tables, Prev: Coding Systems, Up: MULE CCL === - Function: execute-ccl-program CCL-PROGRAM STATUS This function executes CCL-PROGRAM with registers initialized by STATUS. CCL-PROGRAM is a vector of compiled CCL code created by `ccl-compile'. STATUS must be a vector of nine values, specifying the initial value for the R0, R1 .. R7 registers and for the instruction counter IC. A `nil' value for a register initializer causes the register to be set to 0. A `nil' value for the IC initializer causes execution to start at the beginning of the program. When the program is done, STATUS is modified (by side-effect) to contain the ending values for the corresponding registers and IC. - Function: execute-ccl-program-string CCL-PROGRAM STATUS STR This function executes CCL-PROGRAM with initial STATUS on STRING. CCL-PROGRAM is a vector of compiled CCL code created by `ccl-compile'. STATUS must be a vector of nine values, specifying the initial value for the R0, R1 .. R7 registers and for the instruction counter IC. A `nil' value for a register initializer causes the register to be set to 0. A `nil' value for the IC initializer causes execution to start at the beginning of the program. When the program is done, STATUS is modified (by side-effect) to contain the ending values for the corresponding registers and IC. Returns the resulting string. - Function: ccl-reset-elapsed-time This function resets the internal value which holds the time elapsed by CCL interpreter. - Function: ccl-elapsed-time This function returns the time elapsed by CCL interpreter as cons of user and system time. This measures processor time, not real time. Both values are floating point numbers measured in seconds. If only one overall value can be determined, the return value will be a cons of that value and 0. File: lispref.info, Node: Category Tables, Prev: CCL, Up: MULE Category Tables =============== A category table is a type of char table used for keeping track of categories. Categories are used for classifying characters for use in regexps - you can refer to a category rather than having to use a complicated [] expression (and category lookups are significantly faster). There are 95 different categories available, one for each printable character (including space) in the ASCII charset. Each category is designated by one such character, called a "category designator". They are specified in a regexp using the syntax `\cX', where X is a category designator. (This is not yet implemented.) A category table specifies, for each character, the categories that the character is in. Note that a character can be in more than one category. More specifically, a category table maps from a character to either the value `nil' (meaning the character is in no categories) or a 95-element bit vector, specifying for each of the 95 categories whether the character is in that category. Special Lisp functions are provided that abstract this, so you do not have to directly manipulate bit vectors. - Function: category-table-p OBJ This function returns `t' if ARG is a category table. - Function: category-table &optional BUFFER This function returns the current category table. This is the one specified by the current buffer, or by BUFFER if it is non-`nil'. - Function: standard-category-table This function returns the standard category table. This is the one used for new buffers. - Function: copy-category-table &optional TABLE This function constructs a new category table and return it. It is a copy of the TABLE, which defaults to the standard category table. - Function: set-category-table TABLE &optional BUFFER This function selects a new category table for BUFFER. One argument, a category table. BUFFER defaults to the current buffer if omitted. - Function: category-designator-p OBJ This function returns `t' if ARG is a category designator (a char in the range `' '' to `'~''). - Function: category-table-value-p OBJ This function returns `t' if ARG is a category table value. Valid values are `nil' or a bit vector of size 95. File: lispref.info, Node: Tips, Next: Building XEmacs and Object Allocation, Prev: MULE, Up: Top Tips and Standards ****************** This chapter describes no additional features of XEmacs Lisp. Instead it gives advice on making effective use of the features described in the previous chapters. * Menu: * Style Tips:: Writing clean and robust programs. * Compilation Tips:: Making compiled code run fast. * Documentation Tips:: Writing readable documentation strings. * Comment Tips:: Conventions for writing comments. * Library Headers:: Standard headers for library packages. File: lispref.info, Node: Style Tips, Next: Compilation Tips, Up: Tips Writing Clean Lisp Programs =========================== Here are some tips for avoiding common errors in writing Lisp code intended for widespread use: * Since all global variables share the same name space, and all functions share another name space, you should choose a short word to distinguish your program from other Lisp programs. Then take care to begin the names of all global variables, constants, and functions with the chosen prefix. This helps avoid name conflicts. This recommendation applies even to names for traditional Lisp primitives that are not primitives in XEmacs Lisp--even to `cadr'. Believe it or not, there is more than one plausible way to define `cadr'. Play it safe; append your name prefix to produce a name like `foo-cadr' or `mylib-cadr' instead. If you write a function that you think ought to be added to Emacs under a certain name, such as `twiddle-files', don't call it by that name in your program. Call it `mylib-twiddle-files' in your program, and send mail to `bug-gnu-emacs@prep.ai.mit.edu' suggesting we add it to Emacs. If and when we do, we can change the name easily enough. If one prefix is insufficient, your package may use two or three alternative common prefixes, so long as they make sense. Separate the prefix from the rest of the symbol name with a hyphen, `-'. This will be consistent with XEmacs itself and with most Emacs Lisp programs. * It is often useful to put a call to `provide' in each separate library program, at least if there is more than one entry point to the program. * If a file requires certain other library programs to be loaded beforehand, then the comments at the beginning of the file should say so. Also, use `require' to make sure they are loaded. * If one file FOO uses a macro defined in another file BAR, FOO should contain this expression before the first use of the macro: (eval-when-compile (require 'BAR)) (And BAR should contain `(provide 'BAR)', to make the `require' work.) This will cause BAR to be loaded when you byte-compile FOO. Otherwise, you risk compiling FOO without the necessary macro loaded, and that would produce compiled code that won't work right. *Note Compiling Macros::. Using `eval-when-compile' avoids loading BAR when the compiled version of FOO is *used*. * If you define a major mode, make sure to run a hook variable using `run-hooks', just as the existing major modes do. *Note Hooks::. * If the purpose of a function is to tell you whether a certain condition is true or false, give the function a name that ends in `p'. If the name is one word, add just `p'; if the name is multiple words, add `-p'. Examples are `framep' and `frame-live-p'. * If a user option variable records a true-or-false condition, give it a name that ends in `-flag'. * Please do not define `C-c LETTER' as a key in your major modes. These sequences are reserved for users; they are the *only* sequences reserved for users, so we cannot do without them. Instead, define sequences consisting of `C-c' followed by a non-letter. These sequences are reserved for major modes. Changing all the major modes in Emacs 18 so they would follow this convention was a lot of work. Abandoning this convention would make that work go to waste, and inconvenience users. * Sequences consisting of `C-c' followed by `{', `}', `<', `>', `:' or `;' are also reserved for major modes. * Sequences consisting of `C-c' followed by any other punctuation character are allocated for minor modes. Using them in a major mode is not absolutely prohibited, but if you do that, the major mode binding may be shadowed from time to time by minor modes. * You should not bind `C-h' following any prefix character (including `C-c'). If you don't bind `C-h', it is automatically available as a help character for listing the subcommands of the prefix character. * You should not bind a key sequence ending in <ESC> except following another <ESC>. (That is, it is ok to bind a sequence ending in `<ESC> <ESC>'.) The reason for this rule is that a non-prefix binding for <ESC> in any context prevents recognition of escape sequences as function keys in that context. * Applications should not bind mouse events based on button 1 with the shift key held down. These events include `S-mouse-1', `M-S-mouse-1', `C-S-mouse-1', and so on. They are reserved for users. * Modes should redefine `mouse-2' as a command to follow some sort of reference in the text of a buffer, if users usually would not want to alter the text in that buffer by hand. Modes such as Dired, Info, Compilation, and Occur redefine it in this way. * When a package provides a modification of ordinary Emacs behavior, it is good to include a command to enable and disable the feature, Provide a command named `WHATEVER-mode' which turns the feature on or off, and make it autoload (*note Autoload::.). Design the package so that simply loading it has no visible effect--that should not enable the feature. Users will request the feature by invoking the command. * It is a bad idea to define aliases for the Emacs primitives. Use the standard names instead. * Redefining an Emacs primitive is an even worse idea. It may do the right thing for a particular program, but there is no telling what other programs might break as a result. * If a file does replace any of the functions or library programs of standard XEmacs, prominent comments at the beginning of the file should say which functions are replaced, and how the behavior of the replacements differs from that of the originals. * Please keep the names of your XEmacs Lisp source files to 13 characters or less. This way, if the files are compiled, the compiled files' names will be 14 characters or less, which is short enough to fit on all kinds of Unix systems. * Don't use `next-line' or `previous-line' in programs; nearly always, `forward-line' is more convenient as well as more predictable and robust. *Note Text Lines::. * Don't call functions that set the mark, unless setting the mark is one of the intended features of your program. The mark is a user-level feature, so it is incorrect to change the mark except to supply a value for the user's benefit. *Note The Mark::. In particular, don't use these functions: * `beginning-of-buffer', `end-of-buffer' * `replace-string', `replace-regexp' If you just want to move point, or replace a certain string, without any of the other features intended for interactive users, you can replace these functions with one or two lines of simple Lisp code. * Use lists rather than vectors, except when there is a particular reason to use a vector. Lisp has more facilities for manipulating lists than for vectors, and working with lists is usually more convenient. Vectors are advantageous for tables that are substantial in size and are accessed in random order (not searched front to back), provided there is no need to insert or delete elements (only lists allow that). * The recommended way to print a message in the echo area is with the `message' function, not `princ'. *Note The Echo Area::. * When you encounter an error condition, call the function `error' (or `signal'). The function `error' does not return. *Note Signaling Errors::. Do not use `message', `throw', `sleep-for', or `beep' to report errors. * An error message should start with a capital letter but should not end with a period. * Try to avoid using recursive edits. Instead, do what the Rmail `e' command does: use a new local keymap that contains one command defined to switch back to the old local keymap. Or do what the `edit-options' command does: switch to another buffer and let the user switch back at will. *Note Recursive Editing::. * In some other systems there is a convention of choosing variable names that begin and end with `*'. We don't use that convention in Emacs Lisp, so please don't use it in your programs. (Emacs uses such names only for program-generated buffers.) The users will find Emacs more coherent if all libraries use the same conventions. * Indent each function with `C-M-q' (`indent-sexp') using the default indentation parameters. * Don't make a habit of putting close-parentheses on lines by themselves; Lisp programmers find this disconcerting. Once in a while, when there is a sequence of many consecutive close-parentheses, it may make sense to split them in one or two significant places. * Please put a copyright notice on the file if you give copies to anyone. Use the same lines that appear at the top of the Lisp files in XEmacs itself. If you have not signed papers to assign the copyright to the Foundation, then place your name in the copyright notice in place of the Foundation's name. File: lispref.info, Node: Compilation Tips, Next: Documentation Tips, Prev: Style Tips, Up: Tips Tips for Making Compiled Code Fast ================================== Here are ways of improving the execution speed of byte-compiled Lisp programs. * Use the `profile' library to profile your program. See the file `profile.el' for instructions. * Use iteration rather than recursion whenever possible. Function calls are slow in XEmacs Lisp even when a compiled function is calling another compiled function. * Using the primitive list-searching functions `memq', `member', `assq', or `assoc' is even faster than explicit iteration. It may be worth rearranging a data structure so that one of these primitive search functions can be used. * Certain built-in functions are handled specially in byte-compiled code, avoiding the need for an ordinary function call. It is a good idea to use these functions rather than alternatives. To see whether a function is handled specially by the compiler, examine its `byte-compile' property. If the property is non-`nil', then the function is handled specially. For example, the following input will show you that `aref' is compiled specially (*note Array Functions::.) while `elt' is not (*note Sequence Functions::.): (get 'aref 'byte-compile) => byte-compile-two-args (get 'elt 'byte-compile) => nil * If calling a small function accounts for a substantial part of your program's running time, make the function inline. This eliminates the function call overhead. Since making a function inline reduces the flexibility of changing the program, don't do it unless it gives a noticeable speedup in something slow enough that users care about the speed. *Note Inline Functions::. File: lispref.info, Node: Documentation Tips, Next: Comment Tips, Prev: Compilation Tips, Up: Tips Tips for Documentation Strings ============================== Here are some tips for the writing of documentation strings. * Every command, function, or variable intended for users to know about should have a documentation string. * An internal variable or subroutine of a Lisp program might as well have a documentation string. In earlier Emacs versions, you could save space by using a comment instead of a documentation string, but that is no longer the case. * The first line of the documentation string should consist of one or two complete sentences that stand on their own as a summary. `M-x apropos' displays just the first line, and if it doesn't stand on its own, the result looks bad. In particular, start the first line with a capital letter and end with a period. The documentation string can have additional lines that expand on the details of how to use the function or variable. The additional lines should be made up of complete sentences also, but they may be filled if that looks good. * For consistency, phrase the verb in the first sentence of a documentation string as an infinitive with "to" omitted. For instance, use "Return the cons of A and B." in preference to "Returns the cons of A and B." Usually it looks good to do likewise for the rest of the first paragraph. Subsequent paragraphs usually look better if they have proper subjects. * Write documentation strings in the active voice, not the passive, and in the present tense, not the future. For instance, use "Return a list containing A and B." instead of "A list containing A and B will be returned." * Avoid using the word "cause" (or its equivalents) unnecessarily. Instead of, "Cause Emacs to display text in boldface," write just "Display text in boldface." * Do not start or end a documentation string with whitespace. * Format the documentation string so that it fits in an Emacs window on an 80-column screen. It is a good idea for most lines to be no wider than 60 characters. The first line can be wider if necessary to fit the information that ought to be there. However, rather than simply filling the entire documentation string, you can make it much more readable by choosing line breaks with care. Use blank lines between topics if the documentation string is long. * *Do not* indent subsequent lines of a documentation string so that the text is lined up in the source code with the text of the first line. This looks nice in the source code, but looks bizarre when users view the documentation. Remember that the indentation before the starting double-quote is not part of the string! * A variable's documentation string should start with `*' if the variable is one that users would often want to set interactively. If the value is a long list, or a function, or if the variable would be set only in init files, then don't start the documentation string with `*'. *Note Defining Variables::. * The documentation string for a variable that is a yes-or-no flag should start with words such as "Non-nil means...", to make it clear that all non-`nil' values are equivalent and indicate explicitly what `nil' and non-`nil' mean. * When a function's documentation string mentions the value of an argument of the function, use the argument name in capital letters as if it were a name for that value. Thus, the documentation string of the function `/' refers to its second argument as `DIVISOR', because the actual argument name is `divisor'. Also use all caps for meta-syntactic variables, such as when you show the decomposition of a list or vector into subunits, some of which may vary. * When a documentation string refers to a Lisp symbol, write it as it would be printed (which usually means in lower case), with single-quotes around it. For example: `lambda'. There are two exceptions: write t and nil without single-quotes. (In this manual, we normally do use single-quotes for those symbols.) * Don't write key sequences directly in documentation strings. Instead, use the `\\[...]' construct to stand for them. For example, instead of writing `C-f', write `\\[forward-char]'. When Emacs displays the documentation string, it substitutes whatever key is currently bound to `forward-char'. (This is normally `C-f', but it may be some other character if the user has moved key bindings.) *Note Keys in Documentation::. * In documentation strings for a major mode, you will want to refer to the key bindings of that mode's local map, rather than global ones. Therefore, use the construct `\\<...>' once in the documentation string to specify which key map to use. Do this before the first use of `\\[...]'. The text inside the `\\<...>' should be the name of the variable containing the local keymap for the major mode. It is not practical to use `\\[...]' very many times, because display of the documentation string will become slow. So use this to describe the most important commands in your major mode, and then use `\\{...}' to display the rest of the mode's keymap. File: lispref.info, Node: Comment Tips, Next: Library Headers, Prev: Documentation Tips, Up: Tips Tips on Writing Comments ======================== We recommend these conventions for where to put comments and how to indent them: `;' Comments that start with a single semicolon, `;', should all be aligned to the same column on the right of the source code. Such comments usually explain how the code on the same line does its job. In Lisp mode and related modes, the `M-;' (`indent-for-comment') command automatically inserts such a `;' in the right place, or aligns such a comment if it is already present. This and following examples are taken from the Emacs sources. (setq base-version-list ; there was a base (assoc (substring fn 0 start-vn) ; version to which file-version-assoc-list)) ; this looks like ; a subversion `;;' Comments that start with two semicolons, `;;', should be aligned to the same level of indentation as the code. Such comments usually describe the purpose of the following lines or the state of the program at that point. For example: (prog1 (setq auto-fill-function ... ... ;; update modeline (redraw-modeline))) Every function that has no documentation string (because it is use only internally within the package it belongs to), should have instead a two-semicolon comment right before the function, explaining what the function does and how to call it properly. Explain precisely what each argument means and how the function interprets its possible values. `;;;' Comments that start with three semicolons, `;;;', should start at the left margin. Such comments are used outside function definitions to make general statements explaining the design principles of the program. For example: ;;; This Lisp code is run in XEmacs ;;; when it is to operate as a server ;;; for other processes. Another use for triple-semicolon comments is for commenting out lines within a function. We use triple-semicolons for this precisely so that they remain at the left margin. (defun foo (a) ;;; This is no longer necessary. ;;; (force-mode-line-update) (message "Finished with %s" a)) `;;;;' Comments that start with four semicolons, `;;;;', should be aligned to the left margin and are used for headings of major sections of a program. For example: ;;;; The kill ring The indentation commands of the Lisp modes in XEmacs, such as `M-;' (`indent-for-comment') and <TAB> (`lisp-indent-line') automatically indent comments according to these conventions, depending on the number of semicolons. *Note Manipulating Comments: (emacs)Comments. File: lispref.info, Node: Library Headers, Prev: Comment Tips, Up: Tips Conventional Headers for XEmacs Libraries ========================================= XEmacs has conventions for using special comments in Lisp libraries to divide them into sections and give information such as who wrote them. This section explains these conventions. First, an example: ;;; lisp-mnt.el --- minor mode for Emacs Lisp maintainers ;; Copyright (C) 1992 Free Software Foundation, Inc. ;; Author: Eric S. Raymond <esr@snark.thyrsus.com> ;; Maintainer: Eric S. Raymond <esr@snark.thyrsus.com> ;; Created: 14 Jul 1992 ;; Version: 1.2 ;; Keywords: docs ;; This file is part of XEmacs. COPYING PERMISSIONS... The very first line should have this format: ;;; FILENAME --- DESCRIPTION The description should be complete in one line. After the copyright notice come several "header comment" lines, each beginning with `;; HEADER-NAME:'. Here is a table of the conventional possibilities for HEADER-NAME: `Author' This line states the name and net address of at least the principal author of the library. If there are multiple authors, you can list them on continuation lines led by `;;' and a tab character, like this: ;; Author: Ashwin Ram <Ram-Ashwin@cs.yale.edu> ;; Dave Sill <de5@ornl.gov> ;; Dave Brennan <brennan@hal.com> ;; Eric Raymond <esr@snark.thyrsus.com> `Maintainer' This line should contain a single name/address as in the Author line, or an address only, or the string `FSF'. If there is no maintainer line, the person(s) in the Author field are presumed to be the maintainers. The example above is mildly bogus because the maintainer line is redundant. The idea behind the `Author' and `Maintainer' lines is to make possible a Lisp function to "send mail to the maintainer" without having to mine the name out by hand. Be sure to surround the network address with `<...>' if you include the person's full name as well as the network address. `Created' This optional line gives the original creation date of the file. For historical interest only. `Version' If you wish to record version numbers for the individual Lisp program, put them in this line. `Adapted-By' In this header line, place the name of the person who adapted the library for installation (to make it fit the style conventions, for example). `Keywords' This line lists keywords for the `finder-by-keyword' help command. This field is important; it's how people will find your package when they're looking for things by topic area. To separate the keywords, you can use spaces, commas, or both. Just about every Lisp library ought to have the `Author' and `Keywords' header comment lines. Use the others if they are appropriate. You can also put in header lines with other header names--they have no standard meanings, so they can't do any harm. We use additional stylized comments to subdivide the contents of the library file. Here is a table of them: `;;; Commentary:' This begins introductory comments that explain how the library works. It should come right after the copying permissions. `;;; Change log:' This begins change log information stored in the library file (if you store the change history there). For most of the Lisp files distributed with XEmacs, the change history is kept in the file `ChangeLog' and not in the source file at all; these files do not have a `;;; Change log:' line. `;;; Code:' This begins the actual code of the program. `;;; FILENAME ends here' This is the "footer line"; it appears at the very end of the file. Its purpose is to enable people to detect truncated versions of the file from the lack of a footer line. File: lispref.info, Node: Building XEmacs and Object Allocation, Next: Standard Errors, Prev: Tips, Up: Top Building XEmacs; Allocation of Objects ************************************** This chapter describes how the runnable XEmacs executable is dumped with the preloaded Lisp libraries in it and how storage is allocated. There is an entire separate document, the `XEmacs Internals Manual', devoted to the internals of XEmacs from the perspective of the C programmer. It contains much more detailed information about the build process, the allocation and garbage-collection process, and other aspects related to the internals of XEmacs. * Menu: * Building XEmacs:: How to preload Lisp libraries into XEmacs. * Pure Storage:: A kludge to make preloaded Lisp functions sharable. * Garbage Collection:: Reclaiming space for Lisp objects no longer used. File: lispref.info, Node: Building XEmacs, Next: Pure Storage, Up: Building XEmacs and Object Allocation Building XEmacs =============== This section explains the steps involved in building the XEmacs executable. You don't have to know this material to build and install XEmacs, since the makefiles do all these things automatically. This information is pertinent to XEmacs maintenance. The `XEmacs Internals Manual' contains more information about this. Compilation of the C source files in the `src' directory produces an executable file called `temacs', also called a "bare impure XEmacs". It contains the XEmacs Lisp interpreter and I/O routines, but not the editing commands. Before XEmacs is actually usable, a number of Lisp files need to be loaded. These define all the editing commands, plus most of the startup code and many very basic Lisp primitives. This is accomplished by loading the file `loadup.el', which in turn loads all of the other standardly-loaded Lisp files. It takes a substantial time to load the standard Lisp files. Luckily, you don't have to do this each time you run XEmacs; `temacs' can dump out an executable program called `xemacs' that has these files preloaded. `xemacs' starts more quickly because it does not need to load the files. This is the XEmacs executable that is normally installed. To create `xemacs', use the command `temacs -batch -l loadup dump'. The purpose of `-batch' here is to tell `temacs' to run in non-interactive, command-line mode. (`temacs' can *only* run in this fashion. Part of the code required to initialize frames and faces is in Lisp, and must be loaded before XEmacs is able to create any frames.) The argument `dump' tells `loadup.el' to dump a new executable named `xemacs'. The dumping process is highly system-specific, and some operating systems don't support dumping. On those systems, you must start XEmacs with the `temacs -batch -l loadup run-temacs' command each time you use it. This takes a substantial time, but since you need to start Emacs once a day at most--or once a week if you never log out--the extra time is not too severe a problem. (In older versions of Emacs, you started Emacs from `temacs' using `temacs -l loadup'.) You are free to start XEmacs directly from `temacs' if you want, even if there is already a dumped `xemacs'. Normally you wouldn't want to do that; but the Makefiles do this when you rebuild XEmacs using `make all-elc', which builds XEmacs and simultaneously compiles any out-of-date Lisp files. (You need `xemacs' in order to compile Lisp files. However, you also need the compiled Lisp files in order to dump out `xemacs'. If both of these are missing or corrupted, you are out of luck unless you're able to bootstrap `xemacs' from `temacs'. Note that `make all-elc' actually loads the alternative loadup file `loadup-el.el', which works like `loadup.el' but disables the pure-copying process and forces XEmacs to ignore any compiled Lisp files even if they exist.) You can specify additional files to preload by writing a library named `site-load.el' that loads them. You may need to increase the value of `PURESIZE', in `src/puresize.h', to make room for the additional files. You should *not* modify this file directly, however; instead, use the `--puresize' configuration option. (If you run out of pure space while dumping `xemacs', you will be told how much pure space you actually will need.) However, the advantage of preloading additional files decreases as machines get faster. On modern machines, it is often not advisable, especially if the Lisp code is on a file system local to the machine running XEmacs. You can specify other Lisp expressions to execute just before dumping by putting them in a library named `site-init.el'. However, if they might alter the behavior that users expect from an ordinary unmodified XEmacs, it is better to put them in `default.el', so that users can override them if they wish. *Note Start-up Summary::. Before `loadup.el' dumps the new executable, it finds the documentation strings for primitive and preloaded functions (and variables) in the file where they are stored, by calling `Snarf-documentation' (*note Accessing Documentation::.). These strings were moved out of the `xemacs' executable to make it smaller. *Note Documentation Basics::. - Function: dump-emacs TO-FILE FROM-FILE This function dumps the current state of XEmacs into an executable file TO-FILE. It takes symbols from FROM-FILE (this is normally the executable file `temacs'). If you use this function in an XEmacs that was already dumped, you must set `command-line-processed' to `nil' first for good results. *Note Command Line Arguments::. - Function: run-emacs-from-temacs &rest ARGS This is the function that implements the `run-temacs' command-line argument. It is called from `loadup.el' as appropriate. You should most emphatically *not* call this yourself; it will reinitialize your XEmacs process and you'll be sorry. - Command: emacs-version This function returns a string describing the version of XEmacs that is running. It is useful to include this string in bug reports. (emacs-version) => "XEmacs 20.1 [Lucid] (i586-unknown-linux2.0.29) of Mon Apr 7 1997 on altair.xemacs.org" Called interactively, the function prints the same information in the echo area. - Variable: emacs-build-time The value of this variable is the time at which XEmacs was built at the local site. emacs-build-time "Mon Apr 7 20:28:52 1997" => - Variable: emacs-version The value of this variable is the version of Emacs being run. It is a string, e.g. `"20.1 XEmacs Lucid"'. The following two variables did not exist before FSF GNU Emacs version 19.23 and XEmacs version 19.10, which reduces their usefulness at present, but we hope they will be convenient in the future. - Variable: emacs-major-version The major version number of Emacs, as an integer. For XEmacs version 20.1, the value is 20. - Variable: emacs-minor-version The minor version number of Emacs, as an integer. For XEmacs version 20.1, the value is 1. File: lispref.info, Node: Pure Storage, Next: Garbage Collection, Prev: Building XEmacs, Up: Building XEmacs and Object Allocation Pure Storage ============ XEmacs Lisp uses two kinds of storage for user-created Lisp objects: "normal storage" and "pure storage". Normal storage is where all the new data created during an XEmacs session is kept; see the following section for information on normal storage. Pure storage is used for certain data in the preloaded standard Lisp files--data that should never change during actual use of XEmacs. Pure storage is allocated only while `temacs' is loading the standard preloaded Lisp libraries. In the file `xemacs', it is marked as read-only (on operating systems that permit this), so that the memory space can be shared by all the XEmacs jobs running on the machine at once. Pure storage is not expandable; a fixed amount is allocated when XEmacs is compiled, and if that is not sufficient for the preloaded libraries, `temacs' aborts with an error message. If that happens, you must increase the compilation parameter `PURESIZE' using the `--puresize' option to `configure'. This normally won't happen unless you try to preload additional libraries or add features to the standard ones. - Function: purecopy OBJECT This function makes a copy of OBJECT in pure storage and returns it. It copies strings by simply making a new string with the same characters in pure storage. It recursively copies the contents of vectors and cons cells. It does not make copies of other objects such as symbols, but just returns them unchanged. It signals an error if asked to copy markers. This function is a no-op except while XEmacs is being built and dumped; it is usually called only in the file `xemacs/lisp/prim/loaddefs.el', but a few packages call it just in case you decide to preload them. - Variable: pure-bytes-used The value of this variable is the number of bytes of pure storage allocated so far. Typically, in a dumped XEmacs, this number is very close to the total amount of pure storage available--if it were not, we would preallocate less. - Variable: purify-flag This variable determines whether `defun' should make a copy of the function definition in pure storage. If it is non-`nil', then the function definition is copied into pure storage. This flag is `t' while loading all of the basic functions for building XEmacs initially (allowing those functions to be sharable and non-collectible). Dumping XEmacs as an executable always writes `nil' in this variable, regardless of the value it actually has before and after dumping. You should not change this flag in a running XEmacs.