This is ../info/emacs, produced by makeinfo version 4.3 from emacs.texi. This is the Fourteenth edition of the `GNU Emacs Manual', updated for Emacs version 21.3. INFO-DIR-SECTION Emacs START-INFO-DIR-ENTRY * Emacs: (emacs). The extensible self-documenting text editor. END-INFO-DIR-ENTRY Published by the Free Software Foundation 59 Temple Place, Suite 330 Boston, MA 02111-1307 USA Copyright (C) 1985,1986,1987,1993,1994,1995,1996,1997,1998,1999,2000,2001,2002 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being "The GNU Manifesto", "Distribution" and "GNU GENERAL PUBLIC LICENSE", with the Front-Cover texts being "A GNU Manual," and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled "GNU Free Documentation License." (a) The FSF's Back-Cover Text is: "You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development."  File: emacs, Node: C Indent, Next: Custom C Indent, Prev: Lisp Indent, Up: Program Indent Commands for C Indentation -------------------------- Here are special features for indentation in C mode and related modes: `C-c C-q' Reindent the current top-level function definition or aggregate type declaration (`c-indent-defun'). `C-M-q' Reindent each line in the balanced expression that follows point (`c-indent-exp'). A prefix argument inhibits error checking and warning messages about invalid syntax. `' Reindent the current line, and/or in some cases insert a tab character (`c-indent-command'). If `c-tab-always-indent' is `t', this command always reindents the current line and does nothing else. This is the default. If that variable is `nil', this command reindents the current line only if point is at the left margin or in the line's indentation; otherwise, it inserts a tab (or the equivalent number of spaces, if `indent-tabs-mode' is `nil'). Any other value (not `nil' or `t') means always reindent the line, and also insert a tab if within a comment, a string, or a preprocessor directive. To reindent the whole current buffer, type `C-x h C-M-\'. This first selects the whole buffer as the region, then reindents that region. To reindent the current block, use `C-M-u C-M-q'. This moves to the front of the block and then reindents it all.  File: emacs, Node: Custom C Indent, Prev: C Indent, Up: Program Indent Customizing C Indentation ------------------------- C mode and related modes use a simple yet flexible mechanism for customizing indentation. The mechanism works in two steps: first it classifies the line syntactically according to its contents and context; second, it associates each kind of syntactic construct with an indentation offset based on your selected "style". `M-x c-set-style STYLE ' Select predefined indentation style STYLE. A style is a named collection of indentation customizations that can be used in C mode and the related modes. Emacs comes with several predefined styles, including `gnu', `k&r', `bsd', `stroustrup', `linux', `python', `java', `whitesmith', `ellemtel', `cc-mode', and `user'. Some of these styles are primarily intended for one language, but any of them can be used with any of the languages supported by these modes. To find out what a style looks like, select it and reindent some code, e.g., by typing at the start of a function definition. To choose a style for the current buffer, use the command `M-x c-set-style'. Specify a style name as an argument (case is not significant). This command affects the current buffer only, and it affects only future invocations of the indentation commands; it does not reindent the code in the buffer. To reindent the whole buffer in the new style, you can type `C-x h C-M-\'. You can also set the variable `c-default-style' to specify the default style for various major modes. Its value should be an alist, in which each element specifies one major mode and which indentation style to use for it. For example, (setq c-default-style '((java-mode . "java") (other . "gnu"))) specifies an explicit choice for Java mode, and the default `gnu' style for the other C-like modes. This variable takes effect when you select one of the C-like major modes; thus, if you specify a new default style for Java mode, you can make it take effect in an existing Java mode buffer by typing `M-x java-mode' there. The `gnu' style specifies the formatting recommended by the GNU Project for C; it is the default, so as to encourage use of our recommended style. *Note Customizing Indentation: (ccmode)Customizing Indentation, for more information on customizing indentation for C and related modes, including how to override parts of an existing style and how to define your own styles.  File: emacs, Node: Parentheses, Next: Documentation, Prev: Comments, Up: Programs Commands for Editing with Parentheses ===================================== This section describes the commands and features that take advantage of the parenthesis structure in a program, or help you keep it balanced. When talking about these facilities, the term "parenthesis" also includes braces, brackets, or whatever delimiters are defined to match in pairs. The major mode controls which delimiters are significant, through the syntax table (*note Syntax::). In Lisp, only parentheses count; in C, these commands apply to braces and brackets too. You can use `M-x check-parens' to find any unbalanced parentheses and unbalanced string quotes in the buffer. * Menu: * Expressions:: Expressions with balanced parentheses. * Moving by Parens:: Commands for moving up, down and across in the structure of parentheses. * Matching:: Insertion of a close-delimiter flashes matching open.  File: emacs, Node: Expressions, Next: Moving by Parens, Up: Parentheses Expressions with Balanced Parentheses ------------------------------------- These commands deal with balanced expressions, also called "sexps"(1). `C-M-f' Move forward over a balanced expression (`forward-sexp'). `C-M-b' Move backward over a balanced expression(`backward-sexp'). `C-M-k' Kill balanced expression forward (`kill-sexp'). `C-M-' Kill balanced expression backward (`backward-kill-sexp'). `C-M-t' Transpose expressions (`transpose-sexps'). `C-M-@' Put mark after following expression (`mark-sexp'). Each programming language major mode customizes the definition of balanced expressions to suit that language. Balanced expressions typically include symbols, numbers, and string constants, as well as any pair of matching delimiters and their contents. Some languages have obscure forms of expression syntax that nobody has bothered to implement in Emacs. By convention, the keys for these commands are all Control-Meta characters. They usually act on expressions just as the corresponding Meta characters act on words. For instance, the command `C-M-b' moves backward over a balanced expression, just as `M-b' moves back over a word. To move forward over a balanced expression, use `C-M-f' (`forward-sexp'). If the first significant character after point is an opening delimiter (`(' in Lisp; `(', `[' or `{' in C), `C-M-f' moves past the matching closing delimiter. If the character begins a symbol, string, or number, `C-M-f' moves over that. The command `C-M-b' (`backward-sexp') moves backward over a balanced expression. The detailed rules are like those above for `C-M-f', but with directions reversed. If there are prefix characters (single-quote, backquote and comma, in Lisp) preceding the expression, `C-M-b' moves back over them as well. The balanced expression commands move across comments as if they were whitespace, in most modes. `C-M-f' or `C-M-b' with an argument repeats that operation the specified number of times; with a negative argument, it moves in the opposite direction. Killing a whole balanced expression can be done with `C-M-k' (`kill-sexp') or `C-M-' (`backward-kill-sexp'). `C-M-k' kills the characters that `C-M-f' would move over, and `C-M-' kills the characters that `C-M-b' would move over. On some machines, `C-M-' typed on the console is a command to reboot; when that is so, you cannot use it as an Emacs command. This conflict is rare, though: usually the key for Emacs is really , and the reboot command is `C-M-', so there is no conflict. A somewhat random-sounding command which is nevertheless handy is `C-M-t' (`transpose-sexps'), which drags the previous balanced expression across the next one. An argument serves as a repeat count, and a negative argument drags the previous balanced expression backwards across those before it (thus canceling out the effect of `C-M-t' with a positive argument). An argument of zero, rather than doing nothing, transposes the balanced expressions ending at or after point and the mark. To set the region around the next balanced expression in the buffer, use `C-M-@' (`mark-sexp'), which sets mark at the same place that `C-M-f' would move to. `C-M-@' takes arguments like `C-M-f'. In particular, a negative argument is useful for putting the mark at the beginning of the previous balanced expression. In languages that use infix operators, such as C, it is not possible to recognize all balanced expressions as such because there can be multiple possibilities at a given position. For example, C mode does not treat `foo + bar' as a single expression, even though it _is_ one C expression; instead, it recognizes `foo' as one expression and `bar' as another, with the `+' as punctuation between them. Both `foo + bar' and `foo' are legitimate choices for "the expression following point" when point is at the `f', so the expression commands must perforce choose one or the other to operate on. Note that `(foo + bar)' is recognized as a single expression in C mode, because of the parentheses. ---------- Footnotes ---------- (1) The word "sexp" is used to refer to an expression in Lisp.  File: emacs, Node: Moving by Parens, Next: Matching, Prev: Expressions, Up: Parentheses Moving in the Parenthesis Structure ----------------------------------- The Emacs commands for handling parenthetical groupings see nothing except parentheses (or whatever characters must balance in the language you are working with), and the escape characters that might be used to quote those. They are mainly intended for editing programs, but can be useful for editing any text that has parentheses. They are sometimes called "list" commands because in Lisp these groupings are lists. `C-M-n' Move forward over a parenthetical group (`forward-list'). `C-M-p' Move backward over a parenthetical group(`backward-list'). `C-M-u' Move up in parenthesis structure (`backward-up-list'). `C-M-d' Move down in parenthesis structure (`down-list'). The "list" commands `C-M-n' (`forward-list') and `C-M-p' (`backward-list') move over one (or N) parenthetical groupings, skipping blithely over any amount of text that doesn't include meaningful parentheses (symbols, strings, etc.). `C-M-n' and `C-M-p' try to stay at the same level in the parenthesis structure. To move _up_ one (or N) levels, use `C-M-u' (`backward-up-list'). `C-M-u' moves backward up past one unmatched opening delimiter. A positive argument serves as a repeat count; a negative argument reverses the direction of motion, so that the command moves forward and up one or more levels. To move _down_ in the parenthesis structure, use `C-M-d' (`down-list'). In Lisp mode, where `(' is the only opening delimiter, this is nearly the same as searching for a `('. An argument specifies the number of levels to go down.  File: emacs, Node: Matching, Prev: Moving by Parens, Up: Parentheses Automatic Display Of Matching Parentheses ----------------------------------------- The Emacs parenthesis-matching feature is designed to show automatically how parentheses (and other matching delimiters) match in the text. Whenever you type a self-inserting character that is a closing delimiter, the cursor moves momentarily to the location of the matching opening delimiter, provided that is on the screen. If it is not on the screen, Emacs displays some of the text near it in the echo area. Either way, you can tell which grouping you are closing off. If the opening delimiter and closing delimiter are mismatched--such as in `[x)'--a warning message is displayed in the echo area. Three variables control parenthesis match display. `blink-matching-paren' turns the feature on or off: `nil' disables it, but the default is `t' to enable match display. `blink-matching-delay' says how many seconds to leave the cursor on the matching opening delimiter, before bringing it back to the real location of point; the default is 1, but on some systems it is useful to specify a fraction of a second. `blink-matching-paren-distance' specifies how many characters back to search to find the matching opening delimiter. If the match is not found in that distance, scanning stops, and nothing is displayed. This is to prevent the scan for the matching delimiter from wasting lots of time when there is no match. The default is 25600. Show Paren mode provides a more powerful kind of automatic matching. Whenever point is after a closing delimiter, that delimiter and its matching opening delimiter are both highlighted; otherwise, if point is before an opening delimiter, the matching closing delimiter is highlighted. (There is no need to highlight the opening delimiter in that case, because the cursor appears on top of that character.) Use the command `M-x show-paren-mode' to enable or disable this mode. By default, `show-paren-mode' uses colors to highlight the parentheses. However, if your display doesn't support colors, you can customize the faces `show-paren-match-face' and `show-paren-mismatch-face' to use other attributes, such as bold or underline. *Note Face Customization::.  File: emacs, Node: Comments, Next: Parentheses, Prev: Program Indent, Up: Programs Manipulating Comments ===================== Because comments are such an important part of programming, Emacs provides special commands for editing and inserting comments. * Menu: * Comment Commands:: Inserting, killing, and indenting comments. * Multi-Line Comments:: Commands for adding and editing multi-line comments. * Options for Comments::Customizing the comment features.  File: emacs, Node: Comment Commands, Next: Multi-Line Comments, Up: Comments Comment Commands ---------------- The comment commands in this table insert, kill and align comments. They are described in this section and following sections. `M-;' Insert or realign comment on current line; alternatively, comment or uncomment the region (`comment-dwim'). `C-u M-;' Kill comment on current line (`comment-kill'). `C-x ;' Set comment column (`comment-set-column'). `C-M-j' Like followed by inserting and aligning a comment (`comment-indent-new-line'). `M-x comment-region' Add or remove comment delimiters on all the lines in the region. The command to create or align a comment is `M-;' (`comment-dwim'). The word "dwim" is an acronym for "Do What I Mean"; it indicates that this command can be used for many different jobs relating to comments, depending on the situation where you use it. If there is no comment already on the line, `M-;' inserts a new comment, aligned at a specific column called the "comment column". The new comment begins with the string Emacs thinks comments should start with (the value of `comment-start'; see below). Point is after that string, so you can insert the text of the comment right away. If the major mode has specified a string to terminate comments, `M-;' inserts that too, to keep the syntax valid. If the text of the line extends past the comment column, then the comment start string is indented to a suitable boundary (usually, at least one space is inserted). You can also use `M-;' to align an existing comment. If a line already contains the comment-start string, `M-;' reindents it to the conventional alignment and moves point after it. (Exception: comments starting in column 0 are not moved.) Even when an existing comment is properly aligned, `M-;' is still useful for moving directly to the start of the text inside the comment. `C-u M-;' kills any comment on the current line, along with the whitespace before it. To reinsert the comment on another line, move to the end of that line, do `C-y', and then do `M-;' to realign it. Note that `C-u M-;' is not a distinct key; it is `M-;' (`comment-dwim') with a prefix argument. That command is programmed so that when it receives a prefix argument it calls `comment-kill'. However, `comment-kill' is a valid command in its own right, and you can bind it directly to a key if you wish. `M-;' does two other jobs when used with an active region in Transient Mark mode (*note Transient Mark::). Then it either adds or removes comment delimiters on each line of the region. (If every line is a comment, it removes comment delimiters from each; otherwise, it adds comment delimiters to each.) If you are not using Transient Mark mode, then you should use the commands `comment-region' and `uncomment-region' to do these jobs (*note Multi-Line Comments::). A prefix argument used in these circumstances specifies how many comment delimiters to add or how many to delete. Some major modes have special rules for indenting certain kinds of comments in certain contexts. For example, in Lisp code, comments which start with two semicolons are indented as if they were lines of code, instead of at the comment column. Comments which start with three semicolons are supposed to start at the left margin. Emacs understands these conventions by indenting a double-semicolon comment using , and by not changing the indentation of a triple-semicolon comment at all. ;; This function is just an example ;;; Here either two or three semicolons are appropriate. (defun foo (x) ;;; And now, the first part of the function: ;; The following line adds one. (1+ x)) ; This line adds one. In C code, a comment preceded on its line by nothing but whitespace is indented like a line of code.  File: emacs, Node: Multi-Line Comments, Next: Options for Comments, Prev: Comment Commands, Up: Comments Multiple Lines of Comments -------------------------- If you are typing a comment and wish to continue it on another line, you can use the command `C-M-j' (`comment-indent-new-line'). This terminates the comment you are typing, creates a new blank line afterward, and begins a new comment indented under the old one. When Auto Fill mode is on, going past the fill column while typing a comment causes the comment to be continued in just this fashion. If point is not at the end of the line when `C-M-j' is typed, the text on the rest of the line becomes part of the new comment line. To turn existing lines into comment lines, use the `M-x comment-region' command. It adds comment delimiters to the lines that start in the region, thus commenting them out. With a negative argument, it does the opposite--it deletes comment delimiters from the lines in the region. With a positive argument, `comment-region' duplicates the last character of the comment start sequence it adds; the argument specifies how many copies of the character to insert. Thus, in Lisp mode, `C-u 2 M-x comment-region' adds `;;' to each line. Duplicating the comment delimiter is a way of calling attention to the comment. It can also affect how the comment is indented. In Lisp, for proper indentation, you should use an argument of two or three, if between defuns; if within a defun, it must be three.  File: emacs, Node: Options for Comments, Prev: Multi-Line Comments, Up: Comments Options Controlling Comments ---------------------------- The comment column is stored in the variable `comment-column'. You can set it to a number explicitly. Alternatively, the command `C-x ;' (`comment-set-column') sets the comment column to the column point is at. `C-u C-x ;' sets the comment column to match the last comment before point in the buffer, and then does a `M-;' to align the current line's comment under the previous one. The variable `comment-column' is per-buffer: setting the variable in the normal fashion affects only the current buffer, but there is a default value which you can change with `setq-default'. *Note Locals::. Many major modes initialize this variable for the current buffer. The comment commands recognize comments based on the regular expression that is the value of the variable `comment-start-skip'. Make sure this regexp does not match the null string. It may match more than the comment starting delimiter in the strictest sense of the word; for example, in C mode the value of the variable is `"/\\*+ *\\|//+ *""', which matches extra stars and spaces after the `/*' itself, and accepts C++ style comments also. (Note that `\\' is needed in Lisp syntax to include a `\' in the string, which is needed to deny the first star its special meaning in regexp syntax. *Note Regexps::.) When a comment command makes a new comment, it inserts the value of `comment-start' to begin it. The value of `comment-end' is inserted after point, so that it will follow the text that you will insert into the comment. In C mode, `comment-start' has the value `"/* "' and `comment-end' has the value `" */"'. The variable `comment-padding' specifies how many spaces `comment-region' should insert on each line between the comment delimiter and the line's original text. The default is 1, to insert one space. The variable `comment-multi-line' controls how `C-M-j' (`indent-new-comment-line') behaves when used inside a comment. If `comment-multi-line' is `nil', as it normally is, then the comment on the starting line is terminated and a new comment is started on the new following line. If `comment-multi-line' is not `nil', then the new following line is set up as part of the same comment that was found on the starting line. This is done by not inserting a terminator on the old line, and not inserting a starter on the new line. In languages where multi-line comments work, the choice of value for this variable is a matter of taste. The variable `comment-indent-function' should contain a function that will be called to compute the indentation for a newly inserted comment or for aligning an existing comment. It is set differently by various major modes. The function is called with no arguments, but with point at the beginning of the comment, or at the end of a line if a new comment is to be inserted. It should return the column in which the comment ought to start. For example, in Lisp mode, the indent hook function bases its decision on how many semicolons begin an existing comment, and on the code in the preceding lines.  File: emacs, Node: Documentation, Next: Hideshow, Prev: Parentheses, Up: Programs Documentation Lookup ==================== Emacs provides several features you can use to look up the documentation of functions, variables and commands that you plan to use in your program. * Menu: * Info Lookup:: Looking up library functions and commands in Info files. * Man Page:: Looking up man pages of library functions and commands. * Lisp Doc:: Looking up Emacs Lisp functions, etc.  File: emacs, Node: Info Lookup, Next: Man Page, Up: Documentation Info Documentation Lookup ------------------------- For C, Lisp, and other languages that have documentation in Info, you can use `C-h C-i' (`info-lookup-symbol') to view the Info documentation for a symbol. You specify the symbol with the minibuffer; the default is the symbol appearing in the buffer at point. The major mode determines where to look for documentation for the symbol--which Info files to look in, and which indices to search. You can also use `M-x info-lookup-file' to look for documentation for a file name. This feature currently supports the modes Awk, Autoconf, Bison, C, Emacs Lisp, LaTeX, M4, Makefile, Octave, Perl, Scheme, and Texinfo, provided you have installed the relevant Info files, which are typically available with the appropriate GNU package.  File: emacs, Node: Man Page, Next: Lisp Doc, Prev: Info Lookup, Up: Documentation Man Page Lookup --------------- On Unix, the main form of on-line documentation was the "manual page" or "man page". In the GNU operating system, we hope to replace man pages with better-organized manuals that you can browse with Info (*note Misc Help::). This process is not finished, so it is still useful to read manual pages. You can read the man page for an operating system command, library function, or system call, with the `M-x manual-entry' command. It runs the `man' program to format the man page; if the system permits, it runs `man' asynchronously, so that you can keep on editing while the page is being formatted. (On MS-DOS and MS-Windows 3, you cannot edit while Emacs waits for `man' to finish.) The result goes in a buffer named `*Man TOPIC*'. These buffers use a special major mode, Man mode, that facilitates scrolling and jumping to other manual pages. For details, type `C-h m' while in a man page buffer. Each man page belongs to one of ten or more "sections", each named by a digit or by a digit and a letter. Sometimes there are multiple man pages with the same name in different sections. To read a man page from a specific section, type `TOPIC(SECTION)' or `SECTION TOPIC' when `M-x manual-entry' prompts for the topic. For example, to read the man page for the C library function `chmod' (as opposed to a command of the same name), type `M-x manual-entry chmod(2) ' (`chmod' is a system call, so it is in section `2'). If you do not specify a section, the results depend on how the `man' program works on your system. Some of them display only the first man page they find. Others display all man pages that have the specified name, so you can move between them with the `M-n' and `M-p' keys(1). The mode line shows how many manual pages are present in the Man buffer. By default, Emacs highlights the text in man pages. For a long man page, highlighting can take substantial time. You can turn off highlighting of man pages by setting the variable `Man-fontify-manpage-flag' to `nil'. If you insert the text of a man page into an Emacs buffer in some other fashion, you can use the command `M-x Man-fontify-manpage' to perform the same conversions that `M-x manual-entry' does. An alternative way of reading manual pages is the `M-x woman' command(2). Unlike `M-x man', it does not run any external programs to format and display the man pages; instead it does the job in Emacs Lisp, so it works on systems such as MS-Windows, where the `man' program (and the other programs it uses) are not generally available. `M-x woman' prompts for a name of a manual page, and provides completion based on the list of manual pages that are installed on your machine; the list of available manual pages is computed automatically the first time you invoke `woman'. The word at point in the current buffer is used to suggest the default for the name the manual page. With a numeric argument, `M-x woman' recomputes the list of the manual pages used for completion. This is useful if you add or delete manual pages. If you type a name of a manual page and `M-x woman' finds that several manual pages by the same name exist in different sections, it pops up a window with possible candidates asking you to choose one of them. By default, `M-x woman' looks for manual pages in the directories specified in the `MANPATH' environment variable. (If `MANPATH' is not set, `woman' uses a suitable default value, which can be customized.) More precisely, `woman' looks for subdirectories that match the shell wildcard pattern `man*' in each one of these directories, and tries to find the manual pages in those subdirectories. When first invoked, `M-x woman' converts the value of `MANPATH' to a list of directory names and stores that list in the `woman-manpath' variable. Changing the value of this variable is another way to control the list of directories used. You can also augment the list of directories searched by `woman' by setting the value of the `woman-path' variable. This variable should hold a list of specific directories which `woman' should search, in addition to those in `woman-manpath'. Unlike `woman-manpath', the directories in `woman-path' are searched for the manual pages, not for `man*' subdirectories. Occasionally, you might need to display manual pages that are not in any of the directories listed by `woman-manpath' and `woman-path'. The `M-x woman-find-file' command prompts for a name of a manual page file, with completion, and then formats and displays that file like `M-x woman' does. The first time you invoke `M-x woman', it defines the Dired `W' key to run the `woman-find-file' command on the current line's file. You can disable this by setting the variable `woman-dired-keys' to `nil'. *Note Dired::. In addition, the Tar-mode `w' key is define to invoke `woman-find-file' on the current line's archive member. For more information about setting up and using `M-x woman', see *Note WoMan: (woman)Top. ---------- Footnotes ---------- (1) On some systems, the `man' program accepts a `-a' command-line option which tells it to display all the man pages for the specified topic. If you want this behavior, you can add this option to the value of the variable `Man-switches'. (2) The name of the command, `woman', is an acronym for "w/o (without) man," since it doesn't use the `man' program.  File: emacs, Node: Lisp Doc, Prev: Man Page, Up: Documentation Emacs Lisp Documentation Lookup ------------------------------- As you edit Lisp code to be run in Emacs, you can use the commands `C-h f' (`describe-function') and `C-h v' (`describe-variable') to view documentation of functions and variables that you want to use. These commands use the minibuffer to read the name of a function or variable to document, and display the documentation in a window. Their default arguments are based on the code in the neighborhood of point. For `C-h f', the default is the function called in the innermost list containing point. `C-h v' uses the symbol name around or adjacent to point as its default. A more automatic but less powerful method is Eldoc mode. This minor mode constantly displays in the echo area the argument list for the function being called at point. (In other words, it finds the function call that point is contained in, and displays the argument list of that function.) Eldoc mode applies in Emacs Lisp and Lisp Interaction modes only. Use the command `M-x eldoc-mode' to enable or disable this feature.  File: emacs, Node: Hideshow, Next: Symbol Completion, Prev: Documentation, Up: Programs Hideshow minor mode =================== Hideshow minor mode provides selective display of portions of a program, known as "blocks". You can use `M-x hs-minor-mode' to enable or disable this mode, or add `hs-minor-mode' to the mode hook for certain major modes in order to enable it automatically for those modes. Just what constitutes a block depends on the major mode. In C mode or C++ mode, they are delimited by braces, while in Lisp mode and similar modes they are delimited by parentheses. Multi-line comments also count as blocks. `C-c @ C-h' Hide the current block (`hs-hide-block'). `C-c @ C-s' Show the current block (`hs-show-block'). `C-c @ C-c' Either hide or show the current block (`hs-toggle-hiding') `S-Mouse-2' Either hide or show the block you click on (`hs-mouse-toggle-hiding') `C-c @ C-M-h' Hide all top-level blocks (`hs-hide-all'). `C-c @ C-M-s' Show everything in the buffer (`hs-show-all'). `C-c @ C-l' Hide all blocks N levels below this block (`hs-hide-level'). These user options exist for customizing Hideshow mode. `hs-hide-comments-when-hiding-all' Non-`nil' says that `hs-hide-all' should hide comments too. `hs-isearch-open' Specifies what kind of hidden blocks to open in Isearch mode. The value should be one of these four symbols. `code' Open only code blocks. `comment' Open only comments. `t' Open both code blocks and comments. `nil' Open neither code blocks nor comments. `hs-special-modes-alist' A list of elements, each specifying how to initialize Hideshow variables for one major mode. See the variable's documentation string for more information.  File: emacs, Node: Symbol Completion, Next: Glasses, Prev: Hideshow, Up: Programs Completion for Symbol Names =========================== In Emacs, completion is something you normally do in the minibuffer. But one kind of completion is available in all buffers: completion for symbol names. The character `M-' runs a command to complete the partial symbol before point against the set of meaningful symbol names. This command inserts at point any additional characters that it can determine from the partial name. If the partial name in the buffer has multiple possible completions that differ in the very next character, so that it is impossible to complete even one more character, `M-' displays a list of all possible completions in another window. In most programming language major modes, `M-' runs the command `complete-symbol', which provides two kinds of completion. Normally it does completion based on a tags table (*note Tags::); with a numeric argument (regardless of the value), it does completion based on the names listed in the Info file indexes for your language. Thus, to complete the name of a symbol defined in your own program, use `M-' with no argument; to complete the name of a standard library function, use `C-u M-'. Of course, Info-based completion works only if there is an Info file for the standard library functions of your language, and only if it is installed at your site. In Emacs-Lisp mode, the name space for completion normally consists of nontrivial symbols present in Emacs--those that have function definitions, values or properties. However, if there is an open-parenthesis immediately before the beginning of the partial symbol, only symbols with function definitions are considered as completions. The command which implements this is `lisp-complete-symbol'. In Text mode and related modes, `M-' completes words based on the spell-checker's dictionary. *Note Spelling::.  File: emacs, Node: Glasses, Next: Misc for Programs, Prev: Symbol Completion, Up: Programs Glasses minor mode ================== Glasses minor mode makes `unreadableIdentifiersLikeThis' readable by altering the way they display. It knows two different ways to do this: by displaying underscores between a lower-case letter and the following capital letter, and by emboldening the capital letters. It does not alter the buffer text, only the way they display, so you can use it even on read-only buffers. You can use the command `M-x glasses-mode' to enable or disable the mode in the current buffer; you can also add `glasses-mode' to the mode hook of the programming language major modes in which you normally want to use Glasses mode.  File: emacs, Node: Misc for Programs, Next: C Modes, Prev: Glasses, Up: Programs Other Features Useful for Editing Programs ========================================== A number of Emacs commands that aren't designed specifically for editing programs are useful for that nonetheless. The Emacs commands that operate on words, sentences and paragraphs are useful for editing code. Most symbols names contain words (*note Words::); sentences can be found in strings and comments (*note Sentences::). Paragraphs in the strict sense can be found in program code (in long comments), but the paragraph commands are useful in other places too, because programming language major modes define paragraphs to begin and end at blank lines (*note Paragraphs::). Judicious use of blank lines to make the program clearer will also provide useful chunks of text for the paragraph commands to work on. Auto Fill mode, if enabled in a programming language major mode, indents the new lines which it creates. The selective display feature is useful for looking at the overall structure of a function (*note Selective Display::). This feature hides the lines that are indented more than a specified amount. Programming modes often support Outline minor mode (*note Outline Mode::). The Foldout package provides folding-editor features (*note Foldout::). The "automatic typing" features may be useful for writing programs. *Note Autotyping: (autotype)Top.  File: emacs, Node: C Modes, Next: Fortran, Prev: Misc for Programs, Up: Programs C and Related Modes =================== This section gives a brief description of the special features available in C, C++, Objective-C, Java, CORBA IDL, and Pike modes. (These are called "C mode and related modes.") *Note CC Mode: ()Top, for a more extensive description of these modes and their special features. * Menu: * Motion in C:: Commands to move by C statements, etc. * Electric C:: Colon and other chars can automatically reindent. * Hungry Delete:: A more powerful DEL command. * Other C Commands:: Filling comments, viewing expansion of macros, and other neat features. * Comments in C:: Options for customizing comment style.  File: emacs, Node: Motion in C, Next: Electric C, Up: C Modes C Mode Motion Commands ---------------------- This section describes commands for moving point, in C mode and related modes. `C-c C-u' Move point back to the containing preprocessor conditional, leaving the mark behind. A prefix argument acts as a repeat count. With a negative argument, move point forward to the end of the containing preprocessor conditional. When going backwards, `#elif' is treated like `#else' followed by `#if'. When going forwards, `#elif' is ignored. `C-c C-p' Move point back over a preprocessor conditional, leaving the mark behind. A prefix argument acts as a repeat count. With a negative argument, move forward. `C-c C-n' Move point forward across a preprocessor conditional, leaving the mark behind. A prefix argument acts as a repeat count. With a negative argument, move backward. `M-a' Move point to the beginning of the innermost C statement (`c-beginning-of-statement'). If point is already at the beginning of a statement, move to the beginning of the preceding statement. With prefix argument N, move back N - 1 statements. If point is within a string or comment, or next to a comment (only whitespace between them), this command moves by sentences instead of statements. When called from a program, this function takes three optional arguments: the numeric prefix argument, a buffer position limit (don't move back before that place), and a flag that controls whether to do sentence motion when inside of a comment. `M-e' Move point to the end of the innermost C statement; like `M-a' except that it moves in the other direction (`c-end-of-statement'). `M-x c-backward-into-nomenclature' Move point backward to beginning of a C++ nomenclature section or word. With prefix argument N, move N times. If N is negative, move forward. C++ nomenclature means a symbol name in the style of NamingSymbolsWithMixedCaseAndNoUnderlines; each capital letter begins a section or word. In the GNU project, we recommend using underscores to separate words within an identifier in C or C++, rather than using case distinctions. `M-x c-forward-into-nomenclature' Move point forward to end of a C++ nomenclature section or word. With prefix argument N, move N times.  File: emacs, Node: Electric C, Next: Hungry Delete, Prev: Motion in C, Up: C Modes Electric C Characters --------------------- In C mode and related modes, certain printing characters are "electric"--in addition to inserting themselves, they also reindent the current line and may insert newlines. This feature is controlled by the variable `c-auto-newline'. The "electric" characters are `{', `}', `:', `#', `;', `,', `<', `>', `/', `*', `(', and `)'. Electric characters insert newlines only when the "auto-newline" feature is enabled (indicated by `/a' in the mode line after the mode name). This feature is controlled by the variable `c-auto-newline'. You can turn this feature on or off with the command `C-c C-a': `C-c C-a' Toggle the auto-newline feature (`c-toggle-auto-state'). With a prefix argument, this command turns the auto-newline feature on if the argument is positive, and off if it is negative. The colon character is electric because that is appropriate for a single colon. But when you want to insert a double colon in C++, the electric behavior of colon is inconvenient. You can insert a double colon with no reindentation or newlines by typing `C-c :': `C-c :' Insert a double colon scope operator at point, without reindenting the line or adding any newlines (`c-scope-operator'). The electric `#' key reindents the line if it appears to be the beginning of a preprocessor directive. This happens when the value of `c-electric-pound-behavior' is `(alignleft)'. You can turn this feature off by setting `c-electric-pound-behavior' to `nil'. The variable `c-hanging-braces-alist' controls the insertion of newlines before and after inserted braces. It is an association list with elements of the following form: `(SYNTACTIC-SYMBOL . NL-LIST)'. Most of the syntactic symbols that appear in `c-offsets-alist' are meaningful here as well. The list NL-LIST may contain either of the symbols `before' or `after', or both; or it may be `nil'. When a brace is inserted, the syntactic context it defines is looked up in `c-hanging-braces-alist'; if it is found, the NL-LIST is used to determine where newlines are inserted: either before the brace, after, or both. If not found, the default is to insert a newline both before and after braces. The variable `c-hanging-colons-alist' controls the insertion of newlines before and after inserted colons. It is an association list with elements of the following form: `(SYNTACTIC-SYMBOL . NL-LIST)'. The list NL-LIST may contain either of the symbols `before' or `after', or both; or it may be `nil'. When a colon is inserted, the syntactic symbol it defines is looked up in this list, and if found, the NL-LIST is used to determine where newlines are inserted: either before the brace, after, or both. If the syntactic symbol is not found in this list, no newlines are inserted. Electric characters can also delete newlines automatically when the auto-newline feature is enabled. This feature makes auto-newline more acceptable, by deleting the newlines in the most common cases where you do not want them. Emacs can recognize several cases in which deleting a newline might be desirable; by setting the variable `c-cleanup-list', you can specify _which_ of these cases that should happen. The variable's value is a list of symbols, each describing one case for possible deletion of a newline. Here are the meaningful symbols, and their meanings: `brace-catch-brace' Clean up `} catch (CONDITION) {' constructs by placing the entire construct on a single line. The clean-up occurs when you type the `{', if there is nothing between the braces aside from `catch' and CONDITION. `brace-else-brace' Clean up `} else {' constructs by placing the entire construct on a single line. The clean-up occurs when you type the `{' after the `else', but only if there is nothing but white space between the braces and the `else'. `brace-elseif-brace' Clean up `} else if (...) {' constructs by placing the entire construct on a single line. The clean-up occurs when you type the `{', if there is nothing but white space between the `}' and `{' aside from the keywords and the `if'-condition. `empty-defun-braces' Clean up empty defun braces by placing the braces on the same line. Clean-up occurs when you type the closing brace. `defun-close-semi' Clean up the semicolon after a `struct' or similar type declaration, by placing the semicolon on the same line as the closing brace. Clean-up occurs when you type the semicolon. `list-close-comma' Clean up commas following braces in array and aggregate initializers. Clean-up occurs when you type the comma. `scope-operator' Clean up double colons which may designate a C++ scope operator, by placing the colons together. Clean-up occurs when you type the second colon, but only when the two colons are separated by nothing but whitespace.  File: emacs, Node: Hungry Delete, Next: Other C Commands, Prev: Electric C, Up: C Modes Hungry Delete Feature in C -------------------------- When the "hungry-delete" feature is enabled (indicated by `/h' or `/ah' in the mode line after the mode name), a single command deletes all preceding whitespace, not just one space. To turn this feature on or off, use `C-c C-d': `C-c C-d' Toggle the hungry-delete feature (`c-toggle-hungry-state'). With a prefix argument, this command turns the hungry-delete feature on if the argument is positive, and off if it is negative. `C-c C-t' Toggle the auto-newline and hungry-delete features, both at once (`c-toggle-auto-hungry-state'). The variable `c-hungry-delete-key' controls whether the hungry-delete feature is enabled.  File: emacs, Node: Other C Commands, Next: Comments in C, Prev: Hungry Delete, Up: C Modes Other Commands for C Mode ------------------------- `C-M-h' Put mark at the end of a function definition, and put point at the beginning (`c-mark-function'). `M-q' Fill a paragraph, handling C and C++ comments (`c-fill-paragraph'). If any part of the current line is a comment or within a comment, this command fills the comment or the paragraph of it that point is in, preserving the comment indentation and comment delimiters. `C-c C-e' Run the C preprocessor on the text in the region, and show the result, which includes the expansion of all the macro calls (`c-macro-expand'). The buffer text before the region is also included in preprocessing, for the sake of macros defined there, but the output from this part isn't shown. When you are debugging C code that uses macros, sometimes it is hard to figure out precisely how the macros expand. With this command, you don't have to figure it out; you can see the expansions. `C-c C-\' Insert or align `\' characters at the ends of the lines of the region (`c-backslash-region'). This is useful after writing or editing a C macro definition. If a line already ends in `\', this command adjusts the amount of whitespace before it. Otherwise, it inserts a new `\'. However, the last line in the region is treated specially; no `\' is inserted on that line, and any `\' there is deleted. `M-x cpp-highlight-buffer' Highlight parts of the text according to its preprocessor conditionals. This command displays another buffer named `*CPP Edit*', which serves as a graphic menu for selecting how to display particular kinds of conditionals and their contents. After changing various settings, click on `[A]pply these settings' (or go to that buffer and type `a') to rehighlight the C mode buffer accordingly. `C-c C-s' Display the syntactic information about the current source line (`c-show-syntactic-information'). This is the information that directs how the line is indented. `M-x cwarn-mode' `M-x global-cwarn-mode' CWarn minor mode highlights certain suspicious C and C++ constructions: * Assignments inside expressions. * Semicolon following immediately after `if', `for', and `while' (except after a `do ... while' statement); * C++ functions with reference parameters. You can enable the mode for one buffer with the command `M-x cwarn-mode', or for all suitable buffers with the command `M-x global-cwarn-mode' or by customizing the variable `global-cwarn-mode'. You must also enable Font Lock mode to make it work. `M-x hide-ifdef-mode' Hide-ifdef minor mode hides selected code within `#if' and `#ifdef' preprocessor blocks. See the documentation string of `hide-ifdef-mode' for more information. `M-x ff-find-related-file' Find a file "related" in a special way to the file visited by the current buffer. Typically this will be the header file corresponding to a C/C++ source file, or vice versa. The variable `ff-related-file-alist' specifies how to compute related file names.