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This is Info file ../../info/xemacs.info, produced by Makeinfo version 1.68 from the input file xemacs.texi. This file documents the XEmacs editor. Copyright (C) 1985, 1986, 1988 Richard M. Stallman. Copyright (C) 1991, 1992, 1993, 1994 Lucid, Inc. Copyright (C) 1993, 1994 Sun Microsystems, Inc. Copyright (C) 1995 Amdahl Corporation. 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 also that the sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" are 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 sections entitled "The GNU Manifesto", "Distribution" and "GNU General Public License" may be included in a translation approved by the author instead of in the original English. File: xemacs.info, Node: Select Tags Table, Next: Find Tag, Prev: Create Tags Table, Up: Tags Selecting a Tags Table ---------------------- At any time Emacs has one "selected" tags table, and all the commands for working with tags tables use the selected one. To select a tags table, use the variable `tag-table-alist'. The value of `tag-table-alist' is a list that determines which `TAGS' files should be active for a given buffer. This is not really an association list, in that all elements are checked. The car of each element of this list is a pattern against which the buffers file name is compared; if it matches, then the cdr of the list should be the name of the tags table to use. If more than one element of this list matches the buffers file name, all of the associated tags tables are used. Earlier ones are searched first. If the car of elements of this list are strings, they are treated as regular-expressions against which the file is compared (like the `auto-mode-alist'). If they are not strings, they are evaluated. If they evaluate to non-`nil', the current buffer is considered to match. If the cdr of the elements of this list are strings, they are assumed to name a tags file. If they name a directory, the string `tags' is appended to them to get the file name. If they are not strings, they are evaluated and must return an appropriate string. For example: (setq tag-table-alist '(("/usr/src/public/perl/" . "/usr/src/public/perl/perl-3.0/") ("\\.el$" . "/usr/local/emacs/src/") ("/jbw/gnu/" . "/usr15/degree/stud/jbw/gnu/") ("" . "/usr/local/emacs/src/") )) The example defines the tags table alist in the following way: * Anything in the directory `/usr/src/public/perl/' should use the `TAGS' file `/usr/src/public/perl/perl-3.0/TAGS'. * Files ending in `.el' should use the `TAGS' file `/usr/local/emacs/src/TAGS'. * Anything in or below the directory `/jbw/gnu/' should use the `TAGS' file `/usr15/degree/stud/jbw/gnu/TAGS'. If you had a file called `/usr/jbw/foo.el', it would use both `TAGS' files, `/usr/local/emacs/src/TAGS' and `/usr15/degree/stud/jbw/gnu/TAGS' (in that order), because it matches both patterns. If the buffer-local variable `buffer-tag-table' is set, it names a tags table that is searched before all others when `find-tag' is executed from this buffer. If there is a file called `TAGS' in the same directory as the file in question, then that tags file will always be used as well (after the `buffer-tag-table' but before the tables specified by this list). If the variable `tags-file-name' is set, the `TAGS' file it names will apply to all buffers (for backwards compatibility.) It is searched first. If the value of the variable `tags-always-build-completion-table' is `t', the tags file will always be added to the completion table without asking first, regardless of the size of the tags file. The function `M-x visit-tags-table', is largely made obsolete by the variable `tag-table-alist', tells tags commands to use the tags table file FILE first. The FILE should be the name of a file created with the `etags' program. A directory name is also acceptable; it means the file `TAGS' in that directory. The function only stores the file name you provide in the variable `tags-file-name'. Emacs does not actually read in the tags table contents until you try to use them. You can set the variable explicitly instead of using `visit-tags-table'. The value of the variable `tags-file-name' is the name of the tags table used by all buffers. This is for backward compatibility, and is largely supplanted by the variable `tag-table-alist'. File: xemacs.info, Node: Find Tag, Next: Tags Search, Prev: Select Tags Table, Up: Tags Finding a Tag ------------- The most important thing that a tags table enables you to do is to find the definition of a specific tag. `M-. TAG &OPTIONAL OTHER-WINDOW' Find first definition of TAG (`find-tag'). `C-u M-.' Find next alternate definition of last tag specified. `C-x 4 . TAG' Find first definition of TAG, but display it in another window (`find-tag-other-window'). `M-.' (`find-tag') is the command to find the definition of a specified tag. It searches through the tags table for that tag, as a string, then uses the tags table information to determine the file in which the definition is used and the approximate character position of the definition in the file. Then `find-tag' visits the file, moves point to the approximate character position, and starts searching ever-increasing distances away for the text that should appear at the beginning of the definition. If an empty argument is given (by typing <RET>), the sexp in the buffer before or around point is used as the name of the tag to find. *Note Lists::, for information on sexps. The argument to `find-tag' need not be the whole tag name; it can be a substring of a tag name. However, there can be many tag names containing the substring you specify. Since `find-tag' works by searching the text of the tags table, it finds the first tag in the table that the specified substring appears in. To find other tags that match the substring, give `find-tag' a numeric argument, as in `C-u M-.'. This does not read a tag name, but continues searching the tag table's text for another tag containing the same substring last used. If your keyboard has a real <META> key, `M-0 M-.' is an easier alternative to `C-u M-.'. If the optional second argument OTHER-WINDOW is non-`nil', it uses another window to display the tag. Multiple active tags tables and completion are supported. Variables of note include the following: `tag-table-alist' Controls which tables apply to which buffers. `tags-file-name' Stores a default tags table. `tags-build-completion-table' Controls completion behavior. `buffer-tag-table' Specifies a buffer-local table. `make-tags-files-invisible' Sets whether tags tables should be very hidden. `tag-mark-stack-max' Specifies how many tags-based hops to remember. Like most commands that can switch buffers, `find-tag' has another similar command that displays the new buffer in another window. `C-x 4 .' invokes the function `find-tag-other-window'. (This key sequence ends with a period.) Emacs comes with a tags table file `TAGS' (in the directory containing Lisp libraries) that includes all the Lisp libraries and all the C sources of Emacs. By specifying this file with `visit-tags-table' and then using `M-.' you can quickly look at the source of any Emacs function. File: xemacs.info, Node: Tags Search, Next: List Tags, Prev: Find Tag, Up: Tags Searching and Replacing with Tags Tables ---------------------------------------- The commands in this section visit and search all the files listed in the selected tags table, one by one. For these commands, the tags table serves only to specify a sequence of files to search. A related command is `M-x grep' (*note Compilation::.). `M-x tags-search <RET> REGEXP <RET>' Search for REGEXP through the files in the selected tags table. `M-x tags-query-replace <RET> REGEXP <RET> REPLACEMENT <RET>' Perform a `query-replace-regexp' on each file in the selected tags table. `M-,' Restart one of the commands above, from the current location of point (`tags-loop-continue'). `M-x tags-search' reads a regexp using the minibuffer, then searches for matches in all the files in the selected tags table, one file at a time. It displays the name of the file being searched so you can follow its progress. As soon as it finds an occurrence, `tags-search' returns. Having found one match, you probably want to find all the rest. To find one more match, type `M-,' (`tags-loop-continue') to resume the `tags-search'. This searches the rest of the current buffer, followed by the remaining files of the tags table. `M-x tags-query-replace' performs a single `query-replace-regexp' through all the files in the tags table. It reads a regexp to search for and a string to replace with, just like ordinary `M-x query-replace-regexp'. It searches much like `M-x tags-search', but repeatedly, processing matches according to your input. *Note Replace::, for more information on query replace. It is possible to get through all the files in the tags table with a single invocation of `M-x tags-query-replace'. But often it is useful to exit temporarily, which you can do with any input event that has no special query replace meaning. You can resume the query replace subsequently by typing `M-,'; this command resumes the last tags search or replace command that you did. The commands in this section carry out much broader searches than the `find-tag' family. The `find-tag' commands search only for definitions of tags that match your substring or regexp. The commands `tags-search' and `tags-query-replace' find every occurrence of the regexp, as ordinary search commands and replace commands do in the current buffer. These commands create buffers only temporarily for the files that they have to search (those which are not already visited in Emacs buffers). Buffers in which no match is found are quickly killed; the others continue to exist. It may have struck you that `tags-search' is a lot like `grep'. You can also run `grep' itself as an inferior of Emacs and have Emacs show you the matching lines one by one. This works much like running a compilation; finding the source locations of the `grep' matches works like finding the compilation errors. *Note Compilation::. If you wish to process all the files in a selected tags table, but `M-x tags-search' and `M-x tags-query-replace' are not giving you the desired result, you can use `M-x next-file'. `C-u M-x next-file' With a numeric argument, regardless of its value, visit the first file in the tags table and prepare to advance sequentially by files. `M-x next-file' Visit the next file in the selected tags table. File: xemacs.info, Node: List Tags, Prev: Tags Search, Up: Tags Tags Table Inquiries -------------------- `M-x list-tags' Display a list of the tags defined in a specific program file. `M-x tags-apropos' Display a list of all tags matching a specified regexp. `M-x list-tags' reads the name of one of the files described by the selected tags table, and displays a list of all the tags defined in that file. The "file name" argument is really just a string to compare against the names recorded in the tags table; it is read as a string rather than a file name. Therefore, completion and defaulting are not available, and you must enter the string the same way it appears in the tag table. Do not include a directory as part of the file name unless the file name recorded in the tags table contains that directory. `M-x tags-apropos' is like `apropos' for tags. It reads a regexp, then finds all the tags in the selected tags table whose entries match that regexp, and displays the tag names found. File: xemacs.info, Node: Fortran, Next: Asm Mode, Prev: Tags, Up: Programs Fortran Mode ============ Fortran mode provides special motion commands for Fortran statements and subprograms, and indentation commands that understand Fortran conventions of nesting, line numbers, and continuation statements. Special commands for comments are provided because Fortran comments are unlike those of other languages. Built-in abbrevs optionally save typing when you insert Fortran keywords. Use `M-x fortran-mode' to switch to this major mode. Doing so calls the value of `fortran-mode-hook' as a function of no arguments if that variable has a non-`nil' value. * Menu: * Motion: Fortran Motion. Moving point by statements or subprograms. * Indent: Fortran Indent. Indentation commands for Fortran. * Comments: Fortran Comments. Inserting and aligning comments. * Columns: Fortran Columns. Measuring columns for valid Fortran. * Abbrev: Fortran Abbrev. Built-in abbrevs for Fortran keywords. Fortran mode was contributed by Michael Prange. File: xemacs.info, Node: Fortran Motion, Next: Fortran Indent, Prev: Fortran, Up: Fortran Motion Commands --------------- Fortran mode provides special commands to move by subprograms (functions and subroutines) and by statements. There is also a command to put the region around one subprogram, which is convenient for killing it or moving it. `C-M-a' Move to beginning of subprogram (`beginning-of-fortran-subprogram'). `C-M-e' Move to end of subprogram (`end-of-fortran-subprogram'). `C-M-h' Put point at beginning of subprogram and mark at end (`mark-fortran-subprogram'). `C-c C-n' Move to beginning of current or next statement (`fortran-next- statement'). `C-c C-p' Move to beginning of current or previous statement (`fortran- previous-statement'). File: xemacs.info, Node: Fortran Indent, Next: Fortran Comments, Prev: Fortran Motion, Up: Fortran Fortran Indentation ------------------- Special commands and features are available for indenting Fortran code. They make sure various syntactic entities (line numbers, comment line indicators, and continuation line flags) appear in the columns that are required for standard Fortran. * Menu: * Commands: ForIndent Commands. Commands for indenting Fortran. * Numbers: ForIndent Num. How line numbers auto-indent. * Conv: ForIndent Conv. Conventions you must obey to avoid trouble. * Vars: ForIndent Vars. Variables controlling Fortran indent style. File: xemacs.info, Node: ForIndent Commands, Next: ForIndent Num, Prev: Fortran Indent, Up: Fortran Indent Fortran Indentation Commands ............................ `<TAB>' Indent the current line (`fortran-indent-line'). `M-<LFD>' Break the current line and set up a continuation line. `C-M-q' Indent all the lines of the subprogram point is in (`fortran-indent-subprogram'). <TAB> is redefined by Fortran mode to reindent the current line for Fortran (`fortran-indent-line'). Line numbers and continuation markers are indented to their required columns, and the body of the statement is independently indented, based on its nesting in the program. The key `C-M-q' is redefined as `fortran-indent-subprogram', a command that reindents all the lines of the Fortran subprogram (function or subroutine) containing point. The key `M-<LFD>' is redefined as `fortran-split-line', a command to split a line in the appropriate fashion for Fortran. In a non-comment line, the second half becomes a continuation line and is indented accordingly. In a comment line, both halves become separate comment lines. File: xemacs.info, Node: ForIndent Num, Next: ForIndent Conv, Prev: ForIndent Commands, Up: Fortran Indent Line Numbers and Continuation ............................. If a number is the first non-whitespace in the line, it is assumed to be a line number and is moved to columns 0 through 4. (Columns are always counted from 0 in XEmacs.) If the text on the line starts with the conventional Fortran continuation marker `$', it is moved to column 5. If the text begins with any non whitespace character in column 5, it is assumed to be an unconventional continuation marker and remains in column 5. Line numbers of four digits or less are normally indented one space. This amount is controlled by the variable `fortran-line-number-indent', which is the maximum indentation a line number can have. Line numbers are indented to right-justify them to end in column 4 unless that would require more than the maximum indentation. The default value of the variable is 1. Simply inserting a line number is enough to indent it according to these rules. As each digit is inserted, the indentation is recomputed. To turn off this feature, set the variable `fortran-electric-line-number' to `nil'. Then inserting line numbers is like inserting anything else. File: xemacs.info, Node: ForIndent Conv, Next: ForIndent Vars, Prev: ForIndent Num, Up: Fortran Indent Syntactic Conventions ..................... Fortran mode assumes that you follow certain conventions that simplify the task of understanding a Fortran program well enough to indent it properly: * Two nested `do' loops never share a `continue' statement. * The same character appears in column 5 of all continuation lines. It is the value of the variable `fortran-continuation-char'. By default, this character is `$'. If you fail to follow these conventions, the indentation commands may indent some lines unaesthetically. However, a correct Fortran program will retain its meaning when reindented even if the conventions are not followed. File: xemacs.info, Node: ForIndent Vars, Prev: ForIndent Conv, Up: Fortran Indent Variables for Fortran Indentation ................................. Several additional variables control how Fortran indentation works. `fortran-do-indent' Extra indentation within each level of `do' statement (the default is 3). `fortran-if-indent' Extra indentation within each level of `if' statement (the default is 3). `fortran-continuation-indent' Extra indentation for bodies of continuation lines (the default is 5). `fortran-check-all-num-for-matching-do' If this is `nil', indentation assumes that each `do' statement ends on a `continue' statement. Therefore, when computing indentation for a statement other than `continue', it can save time by not checking for a `do' statement ending there. If this is non-`nil', indenting any numbered statement must check for a `do' that ends there. The default is `nil'. `fortran-minimum-statement-indent' Minimum indentation for Fortran statements. For standard Fortran, this is 6. Statement bodies are always indented at least this much. File: xemacs.info, Node: Fortran Comments, Next: Fortran Columns, Prev: Fortran Indent, Up: Fortran Comments -------- The usual Emacs comment commands assume that a comment can follow a line of code. In Fortran, the standard comment syntax requires an entire line to be just a comment. Therefore, Fortran mode replaces the standard Emacs comment commands and defines some new variables. Fortran mode can also handle a non-standard comment syntax where comments start with `!' and can follow other text. Because only some Fortran compilers accept this syntax, Fortran mode will not insert such comments unless you have specified to do so in advance by setting the variable `comment-start' to `"!"' (*note Variables::.). `M-;' Align comment or insert new comment (`fortran-comment-indent'). `C-x ;' Applies to nonstandard `!' comments only. `C-c ;' Turn all lines of the region into comments, or (with arg) turn them back into real code (`fortran-comment-region'). `M-;' in Fortran mode is redefined as the command `fortran-comment-indent'. Like the usual `M-;' command, it recognizes an existing comment and aligns its text appropriately. If there is no existing comment, a comment is inserted and aligned. Inserting and aligning comments is not the same in Fortran mode as in other modes. When a new comment must be inserted, a full-line comment is inserted if the current line is blank. On a non-blank line, a non-standard `!' comment is inserted if you previously specified you wanted to use them. Otherwise a full-line comment is inserted on a new line before the current line. Non-standard `!' comments are aligned like comments in other languages, but full-line comments are aligned differently. In a standard full-line comment, the comment delimiter itself must always appear in column zero. What can be aligned is the text within the comment. You can choose from three styles of alignment by setting the variable `fortran-comment-indent-style' to one of these values: `fixed' The text is aligned at a fixed column, which is the value of `fortran-comment-line-column'. This is the default. `relative' The text is aligned as if it were a line of code, but with an additional `fortran-comment-line-column' columns of indentation. `nil' Text in full-line columns is not moved automatically. You can also specify the character to be used to indent within full-line comments by setting the variable `fortran-comment-indent-char' to the character you want to use. Fortran mode introduces two variables `comment-line-start' and `comment-line-start-skip', which do for full-line comments what `comment-start' and `comment-start-skip' do for ordinary text-following comments. Normally these are set properly by Fortran mode, so you do not need to change them. The normal Emacs comment command `C-x ;' has not been redefined. It can therefore be used if you use `!' comments, but is useless in Fortran mode otherwise. The command `C-c ;' (`fortran-comment-region') turns all the lines of the region into comments by inserting the string `C$$$' at the front of each one. With a numeric arg, the region is turned back into live code by deleting `C$$$' from the front of each line. You can control the string used for the comments by setting the variable `fortran-comment-region'. Note that here we have an example of a command and a variable with the same name; the two uses of the name never conflict because in Lisp and in Emacs it is always clear from the context which one is referred to. File: xemacs.info, Node: Fortran Columns, Next: Fortran Abbrev, Prev: Fortran Comments, Up: Fortran Columns ------- `C-c C-r' Displays a "column ruler" momentarily above the current line (`fortran-column-ruler'). `C-c C-w' Splits the current window horizontally so that it is 72 columns wide. This may help you avoid going over that limit (`fortran-window-create'). The command `C-c C-r' (`fortran-column-ruler') shows a column ruler above the current line. The comment ruler consists of two lines of text that show you the locations of columns with special significance in Fortran programs. Square brackets show the limits of the columns for line numbers, and curly brackets show the limits of the columns for the statement body. Column numbers appear above them. Note that the column numbers count from zero, as always in XEmacs. As a result, the numbers may not be those you are familiar with; but the actual positions in the line are standard Fortran. The text used to display the column ruler is the value of the variable `fortran-comment-ruler'. By changing this variable, you can change the display. For even more help, use `C-c C-w' (`fortran-window-create'), a command which splits the current window horizontally, resulting in a window 72 columns wide. When you edit in this window, you can immediately see when a line gets too wide to be correct Fortran. File: xemacs.info, Node: Fortran Abbrev, Prev: Fortran Columns, Up: Fortran Fortran Keyword Abbrevs ----------------------- Fortran mode provides many built-in abbrevs for common keywords and declarations. These are the same sort of abbrevs that you can define yourself. To use them, you must turn on Abbrev mode. *note Abbrevs::.. The built-in abbrevs are unusual in one way: they all start with a semicolon. You cannot normally use semicolon in an abbrev, but Fortran mode makes this possible by changing the syntax of semicolon to "word constituent". For example, one built-in Fortran abbrev is `;c' for `continue'. If you insert `;c' and then insert a punctuation character such as a space or a newline, the `;c' changes automatically to `continue', provided Abbrev mode is enabled. Type `;?' or `;C-h' to display a list of all built-in Fortran abbrevs and what they stand for. File: xemacs.info, Node: Asm Mode, Prev: Fortran, Up: Programs Asm Mode ======== Asm mode is a major mode for editing files of assembler code. It defines these commands: `<TAB>' `tab-to-tab-stop'. `<LFD>' Insert a newline and then indent using `tab-to-tab-stop'. `:' Insert a colon and then remove the indentation from before the label preceding colon. Then do `tab-to-tab-stop'. `;' Insert or align a comment. The variable `asm-comment-char' specifies which character starts comments in assembler syntax. File: xemacs.info, Node: Running, Next: Abbrevs, Prev: Programs, Up: Top Compiling and Testing Programs ****************************** The previous chapter discusses the Emacs commands that are useful for making changes in programs. This chapter deals with commands that assist in the larger process of developing and maintaining programs. * Menu: * Compilation:: Compiling programs in languages other than Lisp (C, Pascal, etc.) * Modes: Lisp Modes. Various modes for editing Lisp programs, with different facilities for running the Lisp programs. * Libraries: Lisp Libraries. Creating Lisp programs to run in Emacs. * Eval: Lisp Eval. Executing a single Lisp expression in Emacs. * Debug: Lisp Debug. Debugging Lisp programs running in Emacs. * Interaction: Lisp Interaction. Executing Lisp in an Emacs buffer. * External Lisp:: Communicating through Emacs with a separate Lisp. File: xemacs.info, Node: Compilation, Next: Lisp Modes, Prev: Running, Up: Running Running "make", or Compilers Generally ====================================== Emacs can run compilers for non-interactive languages like C and Fortran as inferior processes, feeding the error log into an Emacs buffer. It can also parse the error messages and visit the files in which errors are found, moving point to the line where the error occurred. `M-x compile' Run a compiler asynchronously under Emacs, with error messages to `*compilation*' buffer. `M-x grep' Run `grep' asynchronously under Emacs, with matching lines listed in the buffer named `*compilation*'. `M-x kill-compilation' Kill the process made by the `M-x compile' command. `M-x kill-grep' Kill the running compilation or `grep' subprocess. `C-x `' Visit the next compiler error message or `grep' match. To run `make' or another compiler, type `M-x compile'. This command reads a shell command line using the minibuffer, then executes the specified command line in an inferior shell with output going to the buffer named `*compilation*'. By default, the current buffer's default directory is used as the working directory for the execution of the command; therefore, the makefile comes from this directory. When the shell command line is read, the minibuffer appears containing a default command line (the command you used the last time you typed `M-x compile'). If you type just <RET>, the same command line is used again. The first `M-x compile' provides `make -k' as the default. The default is taken from the variable `compile-command'; if the appropriate compilation command for a file is something other than `make -k', it can be useful to have the file specify a local value for `compile-command' (*note File Variables::.). When you start a compilation, the buffer `*compilation*' is displayed in another window but not selected. Its mode line displays the word `run' or `exit' in the parentheses to tell you whether compilation is finished. You do not have to keep this buffer visible; compilation continues in any case. To kill the compilation process, type `M-x-kill-compilation'. The mode line of the `*compilation*' buffer changes to say `signal' instead of `run'. Starting a new compilation also kills any running compilation, as only one can occur at any time. Starting a new compilation prompts for confirmation before actually killing a compilation that is running. To parse the compiler error messages, type `C-x `' (`next-error'). The character following `C-x' is the grave accent, not the single quote. The command displays the buffer `*compilation*' in one window and the buffer in which the next error occurred in another window. Point in that buffer is moved to the line where the error was found. The corresponding error message is scrolled to the top of the window in which `*compilation*' is displayed. The first time you use `C-x `' after the start of a compilation, it parses all the error messages, visits all the files that have error messages, and creates markers pointing at the lines the error messages refer to. It then moves to the first error message location. Subsequent uses of `C-x `' advance down the data set up by the first use. When the preparsed error messages are exhausted, the next `C-x `' checks for any more error messages that have come in; this is useful if you start editing compiler errors while compilation is still going on. If no additional error messages have come in, `C-x `' reports an error. `C-u C-x `' discards the preparsed error message data and parses the `*compilation*' buffer again, then displays the first error. This way, you can process the same set of errors again. Instead of running a compiler, you can run `grep' and see the lines on which matches were found. To do this, type `M-x grep' with an argument line that contains the same arguments you would give to `grep': a `grep'-style regexp (usually in single quotes to quote the shell's special characters) followed by filenames, which may use wildcard characters. The output from `grep' goes in the `*compilation*' buffer. You can use `C-x `' to find the lines that match as if they were compilation errors. Note: a shell is used to run the compile command, but the shell is not run in interactive mode. In particular, this means that the shell starts up with no prompt. If you find your usual shell prompt making an unsightly appearance in the `*compilation*' buffer, it means you have made a mistake in your shell's initialization file (`.cshrc' or `.shrc' or ...) by setting the prompt unconditionally. The shell initialization file should set the prompt only if there already is a prompt. Here's how to do it in `csh': if ($?prompt) set prompt = ... File: xemacs.info, Node: Lisp Modes, Next: Lisp Libraries, Prev: Compilation, Up: Running Major Modes for Lisp ==================== Emacs has four different major modes for Lisp. They are the same in terms of editing commands, but differ in the commands for executing Lisp expressions. Emacs-Lisp mode The mode for editing source files of programs to run in Emacs Lisp. This mode defines `C-M-x' to evaluate the current defun. *Note Lisp Libraries::. Lisp Interaction mode The mode for an interactive session with Emacs Lisp. It defines <LFD> to evaluate the sexp before point and insert its value in the buffer. *Note Lisp Interaction::. Lisp mode The mode for editing source files of programs that run in other dialects of Lisp than Emacs Lisp. This mode defines `C-M-x' to send the current defun to an inferior Lisp process. *Note External Lisp::. Inferior Lisp mode The mode for an interactive session with an inferior Lisp process. This mode combines the special features of Lisp mode and Shell mode (*note Shell Mode::.). Scheme mode Like Lisp mode but for Scheme programs. Inferior Scheme mode The mode for an interactive session with an inferior Scheme process. File: xemacs.info, Node: Lisp Libraries, Next: Lisp Eval, Prev: Lisp Modes, Up: Running Libraries of Lisp Code for Emacs ================================ Lisp code for Emacs editing commands is stored in files whose names conventionally end in `.el'. This ending tells Emacs to edit them in Emacs-Lisp mode (*note Lisp Modes::.). * Menu: * Loading:: Loading libraries of Lisp code into Emacs for use. * Compiling Libraries:: Compiling a library makes it load and run faster. * Mocklisp:: Converting Mocklisp to Lisp so XEmacs can run it. File: xemacs.info, Node: Loading, Next: Compiling Libraries, Prev: Lisp Libraries, Up: Lisp Libraries Loading Libraries ----------------- `M-x load-file FILE' Load the file FILE of Lisp code. `M-x load-library LIBRARY' Load the library named LIBRARY. `M-x locate-library LIBRARY &optional NOSUFFIX' Show the full path name of Emacs library LIBRARY. To execute a file of Emacs Lisp, use `M-x load-file'. This command reads the file name you provide in the minibuffer, then executes the contents of that file as Lisp code. It is not necessary to visit the file first; in fact, this command reads the file as found on disk, not the text in an Emacs buffer. Once a file of Lisp code is installed in the Emacs Lisp library directories, users can load it using `M-x load-library'. Programs can load it by calling `load-library', or with `load', a more primitive function that is similar but accepts some additional arguments. `M-x load-library' differs from `M-x load-file' in that it searches a sequence of directories and tries three file names in each directory. The three names are: first, the specified name with `.elc' appended; second, the name with `.el' appended; third, the specified name alone. A `.elc' file would be the result of compiling the Lisp file into byte code; if possible, it is loaded in preference to the Lisp file itself because the compiled file loads and runs faster. Because the argument to `load-library' is usually not in itself a valid file name, file name completion is not available. In fact, when using this command, you usually do not know exactly what file name will be used. The sequence of directories searched by `M-x load-library' is specified by the variable `load-path', a list of strings that are directory names. The elements of this list may not begin with "`~'", so you must call `expand-file-name' on them before adding them to the list. The default value of the list contains the directory where the Lisp code for Emacs itself is stored. If you have libraries of your own, put them in a single directory and add that directory to `load-path'. `nil' in this list stands for the current default directory, but it is probably not a good idea to put `nil' in the list. If you start wishing that `nil' were in the list, you should probably use `M-x load-file' for this case. The variable is initialized by the EMACSLOADPATH environment variable. If no value is specified, the variable takes the default value specified in the file `paths.h' when Emacs was built. If a path isn't specified in `paths.h', a default value is obtained from the file system, near the directory in which the Emacs executable resides. Like `M-x load-library', `M-x locate-library' searches the directories in `load-path' to find the file that `M-x load-library' would load. If the optional second argument NOSUFFIX is non-`nil', the suffixes `.elc' or `.el' are not added to the specified name LIBRARY (like calling `load' instead of `load-library'). You often do not have to give any command to load a library, because the commands defined in the library are set up to "autoload" that library. Running any of those commands causes `load' to be called to load the library; this replaces the autoload definitions with the real ones from the library. If autoloading a file does not finish, either because of an error or because of a `C-g' quit, all function definitions made by the file are undone automatically. So are any calls to `provide'. As a consequence, the entire file is loaded a second time if you use one of the autoloadable commands again. This prevents problems when the command is no longer autoloading but is working incorrectly because the file was only partially loaded. Function definitions are undone only for autoloading; explicit calls to `load' do not undo anything if loading is not completed. The variable `after-load-alist' takes an alist of expressions to be evaluated when particular files are loaded. Each element has the form `(FILENAME forms...)'. When `load' is run and the filename argument is FILENAME, the forms in the corresponding element are executed at the end of loading. FILENAME must match exactly. Normally FILENAME is the name of a library, with no directory specified, since that is how load is normally called. An error in `forms' does not undo the load, but it does prevent execution of the rest of the `forms'. File: xemacs.info, Node: Compiling Libraries, Next: Mocklisp, Prev: Loading, Up: Lisp Libraries Compiling Libraries ------------------- Emacs Lisp code can be compiled into byte-code which loads faster, takes up less space when loaded, and executes faster. `M-x batch-byte-compile' Run byte-compile-file on the files remaining on the command line. `M-x byte-compile-buffer &optional BUFFER' Byte-compile and evaluate contents of BUFFER (default is current buffer). `M-x byte-compile-file' Compile a file of Lisp code named FILENAME into a file of byte code. `M-x byte-compile-and-load-file FILENAME' Compile a file of Lisp code named FILENAME into a file of byte code and load it. `M-x byte-recompile-directory DIRECTORY' Recompile every `.el' file in DIRECTORY that needs recompilation. `M-x disassemble' Print disassembled code for OBJECT on (optional) STREAM. `M-x make-obsolete FUNCTION NEW' Make the byte-compiler warn that FUNCTION is obsolete and NEW should be used instead. `byte-compile-file' creates a byte-code compiled file from an Emacs-Lisp source file. The default argument for this function is the file visited in the current buffer. The function reads the specified file, compiles it into byte code, and writes an output file whose name is made by appending `c' to the input file name. Thus, the file `rmail.el' would be compiled into `rmail.elc'. To compile a file of Lisp code named FILENAME into a file of byte code and then load it, use `byte-compile-and-load-file'. To compile and evaluate Lisp code in a given buffer, use `byte-compile-buffer'. To recompile all changed Lisp files in a directory, use `M-x byte-recompile-directory'. Specify just the directory name as an argument. Each `.el' file that has been byte-compiled before is byte-compiled again if it has changed since the previous compilation. A numeric argument to this command tells it to offer to compile each `.el' file that has not been compiled yet. You must answer `y' or `n' to each offer. You can use the function `batch-byte-compile' to invoke Emacs non-interactively from the shell to do byte compilation. When you use this function, the files to be compiled are specified with command-line arguments. Use a shell command of the form: emacs -batch -f batch-byte-compile FILES... Directory names may also be given as arguments; in that case, `byte-recompile-directory' is invoked on each such directory. `batch-byte-compile' uses all remaining command-line arguments as file or directory names, then kills the Emacs process. `M-x disassemble' explains the result of byte compilation. Its argument is a function name. It displays the byte-compiled code in a help window in symbolic form, one instruction per line. If the instruction refers to a variable or constant, that is shown, too. File: xemacs.info, Node: Mocklisp, Prev: Compiling Libraries, Up: Lisp Libraries Converting Mocklisp to Lisp --------------------------- XEmacs can run Mocklisp files by converting them to Emacs Lisp first. To convert a Mocklisp file, visit it and then type `M-x convert-mocklisp-buffer'. Then save the resulting buffer of Lisp file in a file whose name ends in `.el' and use the new file as a Lisp library. You cannot currently byte-compile converted Mocklisp code. The reason is that converted Mocklisp code uses some special Lisp features to deal with Mocklisp's incompatible ideas of how arguments are evaluated and which values signify "true" or "false". File: xemacs.info, Node: Lisp Eval, Next: Lisp Debug, Prev: Lisp Libraries, Up: Running Evaluating Emacs-Lisp Expressions ================================= Lisp programs intended to be run in Emacs should be edited in Emacs-Lisp mode; this will happen automatically for file names ending in `.el'. By contrast, Lisp mode itself should be used for editing Lisp programs intended for other Lisp systems. Emacs-Lisp mode can be selected with the command `M-x emacs-lisp-mode'. For testing of Lisp programs to run in Emacs, it is useful to be able to evaluate part of the program as it is found in the Emacs buffer. For example, if you change the text of a Lisp function definition and then evaluate the definition, Emacs installs the change for future calls to the function. Evaluation of Lisp expressions is also useful in any kind of editing task for invoking non-interactive functions (functions that are not commands). `M-<ESC>' Read a Lisp expression in the minibuffer, evaluate it, and print the value in the minibuffer (`eval-expression'). `C-x C-e' Evaluate the Lisp expression before point, and print the value in the minibuffer (`eval-last-sexp'). `C-M-x' Evaluate the defun containing point or after point, and print the value in the minibuffer (`eval-defun'). `M-x eval-region' Evaluate all the Lisp expressions in the region. `M-x eval-current-buffer' Evaluate all the Lisp expressions in the buffer. `M-<ESC>' (`eval-expression') is the most basic command for evaluating a Lisp expression interactively. It reads the expression using the minibuffer, so you can execute any expression on a buffer regardless of what the buffer contains. When evaluation is complete, the current buffer is once again the buffer that was current when `M-<ESC>' was typed. `M-<ESC>' can easily confuse users, especially on keyboards with autorepeat, where it can result from holding down the <ESC> key for too long. Therefore, `eval-expression' is normally a disabled command. Attempting to use this command asks for confirmation and gives you the option of enabling it; once you enable the command, you are no longer required to confirm. *Note Disabling::. In Emacs-Lisp mode, the key `C-M-x' is bound to the function `eval-defun', which parses the defun containing point or following point as a Lisp expression and evaluates it. The value is printed in the echo area. This command is convenient for installing in the Lisp environment changes that you have just made in the text of a function definition. The command `C-x C-e' (`eval-last-sexp') performs a similar job but is available in all major modes, not just Emacs-Lisp mode. It finds the sexp before point, reads it as a Lisp expression, evaluates it, and prints the value in the echo area. It is sometimes useful to type in an expression and then, with point still after it, type `C-x C-e'. If `C-M-x' or `C-x C-e' are given a numeric argument, they print the value by inserting it into the current buffer at point, rather than in the echo area. The argument value does not matter. The most general command for evaluating Lisp expressions from a buffer is `eval-region'. `M-x eval-region' parses the text of the region as one or more Lisp expressions, evaluating them one by one. `M-x eval-current-buffer' is similar, but it evaluates the entire buffer. This is a reasonable way to install the contents of a file of Lisp code that you are just ready to test. After finding and fixing a bug, use `C-M-x' on each function that you change, to keep the Lisp world in step with the source file. File: xemacs.info, Node: Lisp Debug, Next: Lisp Interaction, Prev: Lisp Eval, Up: Running The Emacs-Lisp Debugger ======================= XEmacs contains a debugger for Lisp programs executing inside it. This debugger is normally not used; many commands frequently get Lisp errors when invoked in inappropriate contexts (such as `C-f' at the end of the buffer) and it would be unpleasant to enter a special debugging mode in this case. When you want to make Lisp errors invoke the debugger, you must set the variable `debug-on-error' to non-`nil'. Quitting with `C-g' is not considered an error, and `debug-on-error' has no effect on the handling of `C-g'. However, if you set `debug-on-quit' to be non-`nil', `C-g' will invoke the debugger. This can be useful for debugging an infinite loop; type `C-g' once the loop has had time to reach its steady state. `debug-on-quit' has no effect on errors. You can make Emacs enter the debugger when a specified function is called or at a particular place in Lisp code. Use `M-x debug-on-entry' with argument FUN-NAME to have Emacs enter the debugger as soon as FUN-NAME is called. Use `M-x cancel-debug-on-entry' to make the function stop entering the debugger when called. (Redefining the function also does this.) To enter the debugger from some other place in Lisp code, you must insert the expression `(debug)' there and install the changed code with `C-M-x'. *Note Lisp Eval::. When the debugger is entered, it displays the previously selected buffer in one window and a buffer named `*Backtrace*' in another window. The backtrace buffer contains one line for each level of Lisp function execution currently going on. At the beginning of the buffer is a message describing the reason that the debugger was invoked, for example, an error message if it was invoked due to an error. The backtrace buffer is read-only and is in Backtrace mode, a special major mode in which letters are defined as debugger commands. The usual Emacs editing commands are available; you can switch windows to examine the buffer that was being edited at the time of the error, and you can switch buffers, visit files, and perform any other editing operations. However, the debugger is a recursive editing level (*note Recursive Edit::.); it is a good idea to return to the backtrace buffer and explictly exit the debugger when you don't want to use it any more. Exiting the debugger kills the backtrace buffer. The contents of the backtrace buffer show you the functions that are executing and the arguments that were given to them. It also allows you to specify a stack frame by moving point to the line describing that frame. The frame whose line point is on is considered the "current frame". Some of the debugger commands operate on the current frame. Debugger commands are mainly used for stepping through code one expression at a time. Here is a list of them: `c' Exit the debugger and continue execution. In most cases, execution of the program continues as if the debugger had never been entered (aside from the effect of any variables or data structures you may have changed while inside the debugger). This includes entry to the debugger due to function entry or exit, explicit invocation, and quitting or certain errors. Most errors cannot be continued; trying to continue an error usually causes the same error to occur again. `d' Continue execution, but enter the debugger the next time a Lisp function is called. This allows you to step through the subexpressions of an expression, and see what the subexpressions do and what values they compute. When you enter the debugger this way, Emacs flags the stack frame for the function call from which you entered. The same function is then called when you exit the frame. To cancel this flag, use `u'. `b' Set up to enter the debugger when the current frame is exited. Frames that invoke the debugger on exit are flagged with stars. `u' Don't enter the debugger when the current frame is exited. This cancels a `b' command on a frame. `e' Read a Lisp expression in the minibuffer, evaluate it, and print the value in the echo area. This is equivalent to the command `M-<ESC>', except that `e' is not normally disabled like `M-<ESC>'. `q' Terminate the program being debugged; return to top-level Emacs command execution. If the debugger was entered due to a `C-g' but you really want to quit, not to debug, use the `q' command. `r' Return a value from the debugger. The value is computed by reading an expression with the minibuffer and evaluating it. The value returned by the debugger makes a difference when the debugger was invoked due to exit from a Lisp call frame (as requested with `b'); then the value specified in the `r' command is used as the value of that frame. The debugger's return value also matters with many errors. For example, `wrong-type-argument' errors will use the debugger's return value instead of the invalid argument; `no-catch' errors will use the debugger value as a throw tag instead of the tag that was not found. If an error was signaled by calling the Lisp function `signal', the debugger's return value is returned as the value of `signal'.