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Info file ../info/emacs, produced by Makeinfo, -*- Text -*- from input file lemacs.tex. This file documents the GNU Emacs editor. Copyright (C) 1985, 1986, 1988 Richard M. Stallman. Copyright (C) 1991, 1992 Lucid, Inc. 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: emacs, Node: Words, Next: Sentences, Prev: Text Mode, Up: Text Words ===== Emacs has commands for moving over or operating on words. By convention, the keys for them are all `Meta-' characters. `M-f' Move forward over a word (`forward-word'). `M-b' Move backward over a word (`backward-word'). `M-d' Kill up to the end of a word (`kill-word'). `M-DEL' Kill back to the beginning of a word (`backward-kill-word'). `M-@' Mark the end of the next word (`mark-word'). `M-t' Transpose two words; drag a word forward or backward across other words (`transpose-words'). Notice how these keys form a series that parallels the character-based `C-f', `C-b', `C-d', `C-t' and DEL. `M-@' is related to `C-@', which is an alias for `C-SPC'. The commands `Meta-f' (`forward-word') and `Meta-b' (`backward-word') move forward and backward over words. They are analogous to `Control-f' and `Control-b', which move over single characters. Like their `Control-' analogues, `Meta-f' and `Meta-b' move several words if given an argument. `Meta-f' with a negative argument moves backward, and `Meta-b' with a negative argument moves forward. Forward motion stop after the last letter of the word, while backward motion stops before the first letter. `Meta-d' (`kill-word') kills the word after point. To be precise, it kills everything from point to the place `Meta-f' would move to. Thus, if point is in the middle of a word, `Meta-d' kills just the part after point. If some punctuation comes between point and the next word, it is killed along with the word. (To kill only the next word but not the punctuation before it, simply type `Meta-f' to get the end, and kill the word backwards with `Meta-DEL'.) `Meta-d' takes arguments just like `Meta-f'. `Meta-DEL' (`backward-kill-word') kills the word before point. It kills everything from point back to where `Meta-b' would move to. If point is after the space in `FOO, BAR', then `FOO, ' is killed. To kill just `FOO', type `Meta-b Meta-d' instead of `Meta-DEL'.) `Meta-t' (`transpose-words') exchanges the word before or containing point with the following word. The delimiter characters between the words do not move. For example, transposing `FOO, BAR' results in `BAR, FOO' rather than `BAR FOO,'. *Note Transpose::, for more on transposition and on arguments to transposition commands. To operate on the next N words with an operation which applies between point and mark, you can either set the mark at point and then move over the words, or you can use the command `Meta-@' (`mark-word') which does not move point, but sets the mark where `Meta-f' would move to. It can be given arguments just like `Meta-f'. The word commands' understanding of syntax is completely controlled by the syntax table. Any character can, for example, be declared to be a word delimiter. *Note Syntax::. File: emacs, Node: Sentences, Next: Paragraphs, Prev: Words, Up: Text Sentences ========= The Emacs commands for manipulating sentences and paragraphs are mostly on `Meta-' keys, and therefore like the word-handling commands. `M-a' Move back to the beginning of the sentence (`backward-sentence'). `M-e' Move forward to the end of the sentence (`forward-sentence'). `M-k' Kill forward to the end of the sentence (`kill-sentence'). `C-x DEL' Kill back to the beginning of the sentence (`backward-kill-sentence'). The commands `Meta-a' and `Meta-e' (`backward-sentence' and `forward-sentence') move to the beginning and end of the current sentence, respectively. They resemble `Control-a' and `Control-e', which move to the beginning and end of a line. Unlike their counterparts, `Meta-a' and `Meta-e' move over successive sentences if repeated or given numeric arguments. Emacs assumes the typist's convention is followed, and thus considers a sentence to end wherever there is a `.', `?' or `!' followed by the end of a line or two spaces, with any number of `)', `]', `'', or `"' characters allowed in between. A sentence also begins or ends wherever a paragraph begins or ends. Neither `M-a' nor `M-e' moves past the newline or spaces beyond the sentence edge at which it is stopping. `M-a' and `M-e' have a corresponding kill command, just like `C-a' and `C-e' have `C-k'. The command is `M-k' (`kill-sentence') which kills from point to the end of the sentence. With minus one as an argument it kills back to the beginning of the sentence. Larger arguments serve as repeat counts. There is a special command, `C-x DEL' (`backward-kill-sentence') for killing back to the beginning of a sentence, which is useful when you change your mind in the middle of composing text. The variable `sentence-end' controls recognition of the end of a sentence. It is a regexp that matches the last few characters of a sentence, together with the whitespace following the sentence. Its normal value is "[.?!][]\"')]*\$$\\|\t\\| \$[ \t\n]*" This example is explained in the section on regexps. *Note Regexps::. File: emacs, Node: Paragraphs, Next: Pages, Prev: Sentences, Up: Text Paragraphs ========== The Emacs commands for manipulating paragraphs are also `Meta-' keys. `M-[' Move back to previous paragraph beginning (`backward-paragraph'). `M-]' Move forward to next paragraph end (`forward-paragraph'). `M-h' Put point and mark around this or next paragraph (`mark-paragraph'). `Meta-[' moves to the beginning of the current or previous paragraph, while `Meta-]' moves to the end of the current or next paragraph. Blank lines and text formatter command lines separate paragraphs and are not part of any paragraph. An indented line starts a new paragraph. In major modes for programs (as opposed to Text mode), paragraphs begin and end only at blank lines. As a result, the paragraph commands continue to be useful even though there are no paragraphs per se. When there is a fill prefix, paragraphs are delimited by all lines which don't start with the fill prefix. *Note Filling::. To operate on a paragraph, you can use the command `Meta-h' (`mark-paragraph') to set the region around it. This command puts point at the beginning and mark at the end of the paragraph point was in. If point is between paragraphs (in a run of blank lines, or at a boundary), the paragraph following point is surrounded by point and mark. If there are blank lines preceding the first line of the paragraph, one of the blank lines is included in the region. Thus, for example, `M-h C-w' kills the paragraph around or after point. The precise definition of a paragraph boundary is controlled by the variables `paragraph-separate' and `paragraph-start'. The value of `paragraph-start' is a regexp that matches any line that either starts or separates paragraphs. The value of `paragraph-separate' is another regexp that matches only lines that separate paragraphs without being part of any paragraph. Lines that start a new paragraph and are contained in it must match both regexps. For example, normally `paragraph-start' is `"^[ \t\n\f]"' and `paragraph-separate' is `"^[ \t\f]*$"'. Normally it is desirable for page boundaries to separate paragraphs. The default values of these variables recognize the usual separator for pages. File: emacs, Node: Pages, Next: Filling, Prev: Paragraphs, Up: Text Pages ===== Files are often thought of as divided into "pages" by the "formfeed" character (ASCII Control-L, octal code 014). For example, if a file is printed on a line printer, each "page" of the file starts on a new page of paper. Emacs treats a page-separator character just like any other character. It can be inserted with `C-q C-l', or deleted with DEL. You are free to paginate your file or not. However, since pages are often meaningful divisions of the file, commands are provided to move over them and operate on them. `C-x [' Move point to previous page boundary (`backward-page'). `C-x ]' Move point to next page boundary (`forward-page'). `C-x C-p' Put point and mark around this page (or another page) (`mark-page'). `C-x l' Count the lines in this page (`count-lines-page'). The `C-x [' (`backward-page') command moves point to immediately after the previous page delimiter. If point is already right after a page delimiter, the command skips that one and stops at the previous one. A numeric argument serves as a repeat count. The `C-x ]' (`forward-page') command moves forward past the next page delimiter. The `C-x C-p' command (`mark-page') puts point at the beginning of the current page and the mark at the end. The page delimiter at the end is included (the mark follows it). The page delimiter at the front is excluded (point follows it). You can follow this command by `C-w' to kill a page you want to move elsewhere. If you insert the page after a page delimiter, at a place where `C-x ]' or `C-x [' would take you, the page will be properly delimited before and after once again. A numeric argument to `C-x C-p' is used to specify which page to go to, relative to the current one. Zero means the current page. One means the next page, and -1 means the previous one. The `C-x l' command (`count-lines-page') can help you decide where to break a page in two. It prints the total number of lines in the current page in the echo area, then divides the lines into those preceding the current line and those following it, for example Page has 96 (72+25) lines Notice that the sum is off by one; this is correct if point is not at the beginning of a line. The variable `page-delimiter' should have as its value a regexp that matches the beginning of a line that separates pages. This defines where pages begin. The normal value of this variable is `"^\f"', which matches a formfeed character at the beginning of a line. File: emacs, Node: Filling, Next: Case, Prev: Pages, Up: Text Filling Text ============ If you use Auto Fill mode, Emacs "fills" text (breaks it up into lines that fit in a specified width) as you insert it. When you alter existing text it is often no longer be properly filled afterwards and you can use explicit commands for filling. * Menu: * Auto Fill:: Auto Fill mode breaks long lines automatically. * Fill Commands:: Commands to refill paragraphs and center lines. * Fill Prefix:: Filling when every line is indented or in a comment, etc. File: emacs, Node: Auto Fill, Next: Fill Commands, Prev: Filling, Up: Filling Auto Fill Mode -------------- "Auto Fill" mode is a minor mode in which lines are broken automatically when they become too wide. Breaking happens only when you type a SPC or RET. `M-x auto-fill-mode' Enable or disable Auto Fill mode. `SPC' `RET' In Auto Fill mode, break lines when appropriate. `M-x auto-fill-mode' turns Auto Fill mode on if it was off, or off if it was on. With a positive numeric argument the command always turns Auto Fill mode on, and with a negative argument it always turns it off. The presence of the word `Fill' in the mode line, inside the parentheses, indicates that Auto Fill mode is in effect. Auto Fill mode is a minor mode; you can turn it on or off for each buffer individually. *Note Minor Modes::. In Auto Fill mode, lines are broken automatically at spaces when they get longer than desired. Line breaking and rearrangement takes place only when you type SPC or RET. To insert a space or newline without permitting line-breaking, type `C-q SPC' or `C-q LFD' (recall that a newline is really a linefeed). `C-o' inserts a newline without line breaking. Auto Fill mode works well with Lisp mode: when it makes a new line in Lisp mode it indents that line with TAB. If a line ending in a Lisp comment gets too long, the text of the comment is split into two comment lines. Optionally new comment delimiters are inserted at the end of the first line and the beginning of the second, so that each line is a separate comment. The variable `comment-multi-line' controls the choice (*note Comments::.). Auto Fill mode does not refill entire paragraphs. It can break lines but cannot merge lines. Editing in the middle of a paragraph can result in a paragraph that is not correctly filled. The easiest way to make the paragraph properly filled again is using an explicit fill commands. Many users like Auto Fill mode and want to use it in all text files. The section on init files explains how you can arrange this permanently for yourself. *Note Init File::. File: emacs, Node: Fill Commands, Next: Fill Prefix, Prev: Auto Fill, Up: Filling Explicit Fill Commands ---------------------- `M-q' Fill current paragraph (`fill-paragraph'). `M-g' Fill each paragraph in the region (`fill-region'). `C-x f' Set the fill column (`set-fill-column'). `M-x fill-region-as-paragraph.' Fill the region, considering it as one paragraph. `M-s' Center a line. To refill a paragraph, use the command `Meta-q' (`fill-paragraph'). It causes the paragraph containing point, or the one after point if point is between paragraphs, to be refilled. All line breaks are removed, and new ones are inserted where necessary. `M-q' can be undone with `C-_'. *Note Undo::. To refill many paragraphs, use `M-g' (`fill-region'), which divides the region into paragraphs and fills each of them. `Meta-q' and `Meta-g' use the same criteria as `Meta-h' for finding paragraph boundaries (*note Paragraphs::.). For more control, you can use `M-x fill-region-as-paragraph', which refills everything between point and mark. This command recognizes only blank lines as paragraph separators. A numeric argument to `M-g' or `M-q' causes it to "justify" the text as well as filling it. Extra spaces are inserted to make the right margin line up exactly at the fill column. To remove the extra spaces, use `M-q' or `M-g' with no argument. The variable `auto-fill-inhibit-regexp'takes as a value a regexp to match lines that should not be auto-filled. The command `Meta-s' (`center-line') centers the current line within the current fill column. With an argument, it centers several lines individually and moves past them. The maximum line width for filling is in the variable `fill-column'. Altering the value of `fill-column' makes it local to the current buffer; until then, the default value--initially 70--is in effect. *Note Locals::. The easiest way to set `fill-column' is to use the command `C-x f' (`set-fill-column'). With no argument, it sets `fill-column' to the current horizontal position of point. With a numeric argument, it uses that number as the new fill column. File: emacs, Node: Fill Prefix, Prev: Fill Commands, Up: Filling The Fill Prefix --------------- To fill a paragraph in which each line starts with a special marker (which might be a few spaces, giving an indented paragraph), use the "fill prefix" feature. The fill prefix is a string which is not included in filling. Emacs expects every line to start with a fill prefix. `C-x .' Set the fill prefix (`set-fill-prefix'). `M-q' Fill a paragraph using current fill prefix (`fill-paragraph'). `M-x fill-individual-paragraphs' Fill the region, considering each change of indentation as starting a new paragraph. To specify a fill prefix, move to a line that starts with the desired prefix, put point at the end of the prefix, and give the command `C-x .' (`set-fill-prefix'). That's a period after the `C-x'. To turn off the fill prefix, specify an empty prefix: type `C-x .' with point at the beginning of a line. When a fill prefix is in effect, the fill commands remove the fill prefix from each line before filling and insert it on each line after filling. Auto Fill mode also inserts the fill prefix inserted on new lines it creates. Lines that do not start with the fill prefix are considered to start paragraphs, both in `M-q' and the paragraph commands; this is just right if you are using paragraphs with hanging indentation (every line indented except the first one). Lines which are blank or indented once the prefix is removed also separate or start paragraphs; this is what you want if you are writing multi-paragraph comments with a comment delimiter on each line. The fill prefix is stored in the variable `fill-prefix'. Its value is a string, or `nil' when there is no fill prefix. This is a per-buffer variable; altering the variable affects only the current buffer, but there is a default value which you can change as well. *Note Locals::. Another way to use fill prefixes is through `M-x fill-individual-paragraphs'. This function divides the region into groups of consecutive lines with the same amount and kind of indentation and fills each group as a paragraph, using its indentation as a fill prefix. File: emacs, Node: Case, Prev: Filling, Up: Text Case Conversion Commands ======================== Emacs has commands for converting either a single word or any arbitrary range of text to upper case or to lower case. `M-l' Convert following word to lower case (`downcase-word'). `M-u' Convert following word to upper case (`upcase-word'). `M-c' Capitalize the following word (`capitalize-word'). `C-x C-l' Convert region to lower case (`downcase-region'). `C-x C-u' Convert region to upper case (`upcase-region'). The word conversion commands are used most frequently. `Meta-l' (`downcase-word') converts the word after point to lower case, moving past it. Thus, repeating `Meta-l' converts successive words. `Meta-u' (`upcase-word') converts to all capitals instead, while `Meta-c' (`capitalize-word') puts the first letter of the word into upper case and the rest into lower case. The word conversion commands convert several words at once if given an argument. They are especially convenient for converting a large amount of text from all upper case to mixed case: you can move through the text using `M-l', `M-u' or `M-c' on each word as appropriate, occasionally using `M-f' instead to skip a word. When given a negative argument, the word case conversion commands apply to the appropriate number of words before point, but do not move point. This is convenient when you have just typed a word in the wrong case: you can give the case conversion command and continue typing. If a word case conversion command is given in the middle of a word, it applies only to the part of the word which follows point. This is just like what `Meta-d' (`kill-word') does. With a negative argument, case conversion applies only to the part of the word before point. The other case conversion commands are `C-x C-u' (`upcase-region') and `C-x C-l' (`downcase-region'), which convert everything between point and mark to the specified case. Point and mark do not move. File: emacs, Node: Programs, Next: Running, Prev: Text, Up: Top Editing Programs **************** Emacs has many commands designed to understand the syntax of programming languages such as Lisp and C. These commands can * Move over or kill balanced expressions or "sexps" (*note Lists::.). * Move over or mark top-level balanced expressions ("defuns", in Lisp; functions, in C). * Show how parentheses balance (*note Matching::.). * Insert, kill or align comments (*note Comments::.). * Follow the usual indentation conventions of the language (*note Grinding::.). The commands available for words, sentences and paragraphs are useful in editing code even though their canonical application is for editing human language text. Most symbols contain words (*note Words::.); sentences can be found in strings and comments (*note Sentences::.). Paragraphs per se are not present in code, but the paragraph commands are useful anyway, because Lisp mode and C mode define paragraphs to begin and end at blank lines (*note Paragraphs::.). Judicious use of blank lines to make the program clearer also provides interesting chunks of text for the paragraph commands to work on. The selective display feature is useful for looking at the overall structure of a function (*note Selective Display::.). This feature causes only the lines that are indented less than a specified amount to appear on the screen. * Menu: * Program Modes:: Major modes for editing programs. * Lists:: Expressions with balanced parentheses. There are editing commands to operate on them. * Defuns:: Each program is made up of separate functions. There are editing commands to operate on them. * Grinding:: Adjusting indentation to show the nesting. * Matching:: Insertion of a close-delimiter flashes matching open. * Comments:: Inserting, illing and aligning comments. * Balanced Editing:: Inserting two matching parentheses at once, etc. * Lisp Completion:: Completion on symbol names in Lisp code. * Documentation:: Getting documentation of functions you plan to call. * Change Log:: Maintaining a change history for your program. * Tags:: Go direct to any function in your program in one command. Tags remembers which file it is in. * Fortran:: Fortran mode and its special features. File: emacs, Node: Program Modes, Next: Lists, Prev: Programs, Up: Programs Major Modes for Programming Languages ===================================== Emacs has several major modes for the programming languages Lisp, Scheme (a variant of Lisp), C, Fortran and Muddle. Ideally, a major mode should be implemented for each programming language you might want to edit with Emacs; but often the mode for one language can serve for other syntactically similar languages. The language modes that exist are those that someone decided to take the trouble to write. There are several variants of Lisp mode, which differ in the way they interface to Lisp execution. *Note Lisp Modes::. Each of the programming language modes defines the TAB key to run an indentation function that knows the indentation conventions of that language and updates the current line's indentation accordingly. For example, in C mode TAB is bound to `c-indent-line'. LFD is normally defined to do RET followed by TAB; thus, it too indents in a mode-specific fashion. In most programming languages, indentation is likely to vary from line to line. So the major modes for those languages rebind DEL to treat a tab as if it were the equivalent number of spaces (using the command `backward-delete-char-untabify'). This makes it possible to rub out indentation one column at a time without worrying whether it is made up of spaces or tabs. In these modes, use `C-b C-d' to delete a tab character before point. Programming language modes define paragraphs to be separated only by blank lines, so that the paragraph commands remain useful. Auto Fill mode, if enabled in a programming language major mode, indents the new lines which it creates. Turning on a major mode calls a user-supplied function called the "mode hook", which is the value of a Lisp variable. For example, turning on C mode calls the value of the variable `c-mode-hook' if that value exists and is non-`nil'. Mode hook variables for other programming language modes include `lisp-mode-hook', `emacs-lisp-mode-hook', `lisp-interaction-mode-hook', `scheme-mode-hook' and `muddle-mode-hook'. The mode hook function receives no arguments. File: emacs, Node: Lists, Next: Defuns, Prev: Program Modes, Up: Programs Lists and Sexps =============== By convention, Emacs keys for dealing with balanced expressions are usually `Control-Meta-' characters. They tend to be analogous in function to their `Control-' and `Meta-' equivalents. These commands are usually thought of as pertaining to expressions in programming languages, but can be useful with any language in which some sort of parentheses exist (including English). The commands fall into two classes. Some commands deal only with "lists" (parenthetical groupings). They see nothing except parentheses, brackets, braces (depending on what must balance in the language you are working with), and escape characters that might be used to quote those. The other commands deal with expressions or "sexps". The word `sexp' is derived from "s-expression", the term for an expression in Lisp. In Emacs, the notion of `sexp' is not limited to Lisp. It refers to an expression in the language your program is written in. Each programming language has its own major mode, which customizes the syntax tables so that expressions in that language count as sexps. Sexps typically include symbols, numbers, and string constants, as well as anything contained in parentheses, brackets or braces. In languages that use prefix and infix operators, such as C, it is not possible for all expressions to be sexps. For example, C mode does not recognize `foo + bar' as an sexp, even though it is a C expression; it recognizes `foo' as one sexp and `bar' as another, with the `+' as punctuation between them. This is a fundamental ambiguity: both `foo + bar' and `foo' are legitimate choices for the sexp to move over if point is at the `f'. Note that `(foo + bar)' is a sexp in C mode. Some languages have obscure forms of syntax for expressions that nobody has bothered to make Emacs understand properly. `C-M-f' Move forward over an sexp (`forward-sexp'). `C-M-b' Move backward over an sexp (`backward-sexp'). `C-M-k' Kill sexp forward (`kill-sexp'). `C-M-u' Move up and backward in list structure (`backward-up-list'). `C-M-d' Move down and forward in list structure (`down-list'). `C-M-n' Move forward over a list (`forward-list'). `C-M-p' Move backward over a list (`backward-list'). `C-M-t' Transpose expressions (`transpose-sexps'). `C-M-@' Put mark after following expression (`mark-sexp'). To move forward over an sexp, 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. If the character after point is a closing delimiter, `C-M-f' just moves past it. (This last is not really moving across an sexp; it is an exception which is included in the definition of `C-M-f' because it is as useful a behavior as anyone can think of for that situation.) The command `C-M-b' (`backward-sexp') moves backward over a sexp. The detailed rules are like those above for `C-M-f', but with directions reversed. If there are any prefix characters (singlequote, backquote and comma, in Lisp) preceding the sexp, `C-M-b' moves back over them as well. `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. In languages such as C where the comment-terminator can be recognized, the sexp commands move across comments as if they were whitespace. In Lisp, and other languages where comments run until the end of a line, it is very difficult to ignore comments when parsing backwards; therefore, in such languages the sexp commands treat the text of comments as if it were code. Killing an sexp at a time can be done with `C-M-k' (`kill-sexp'). `C-M-k' kills the characters that `C-M-f' would move over. The "list commands", `C-M-n' (`forward-list') and `C-M-p' (`backward-list'), move over lists like the sexp commands but skip over any number of other kinds of sexps (symbols, strings, etc). In some situations, these commands are useful because they usually ignore comments, since the comments usually do not contain any lists. `C-M-n' and `C-M-p' stay at the same level in parentheses, when that is possible. 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 direction of motion and also requests repetition, so it moves forward and up one or more levels. To move down in list 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 of parentheses to go down. `C-M-t' (`transpose-sexps') drags the previous sexp across the next one. An argument serves as a repeat count, and a negative argument drags backwards (thus canceling out the effect of `C-M-t' with a positive argument). An argument of zero, rather than doing nothing, transposes the sexps ending after point and the mark. To make the region be the next sexp in the buffer, use `C-M-@' (`mark-sexp') which sets the 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 sexp. The list and sexp commands' understanding of syntax is completely controlled by the syntax table. Any character can, for example, be declared to be an opening delimiter and act like an open parenthesis. *Note Syntax::. File: emacs, Node: Defuns, Next: Grinding, Prev: Lists, Up: Programs Defuns ====== In Emacs, a parenthetical grouping at the top level in the buffer is called a "defun". The name derives from the fact that most top-level lists in a Lisp file are instances of the special form `defun', but in Emacs terminology, any top-level parenthetical grouping counts as a defun regardless of its contents, and regardless of the programming language in use. For example, in C, the body of a function definition is a defun. `C-M-a' Move to beginning of current or preceding defun (`beginning-of-defun'). `C-M-e' Move to end of current or following defun (`end-of-defun'). `C-M-h' Put region around whole current or following defun (`mark-defun'). The commands to move to the beginning and end of the current defun are `C-M-a' (`beginning-of-defun') and `C-M-e' (`end-of-defun'). To operate on the current defun, use `C-M-h' (`mark-defun') which puts point at the beginning and the mark at the end of the current or next defun. This is the easiest way to prepare for moving the defun to a different place. In C mode, `C-M-h' runs the function `mark-c-function', which is almost the same as `mark-defun', but which backs up over the argument declarations, function name, and returned data type so that the entire C function is inside th e region. To compile and evaluate the current defun, use `M-x elisp-compile-defun'. This function prints the results in the minibuffer. If you include an argument, it inserts the value in the current buffer after the defun. Emacs assumes that any open-parenthesis found in the leftmost column is the start of a defun. Therefore, never put an open-parenthesis at the left margin in a Lisp file unless it is the start of a top level list. Never put an open-brace or other opening delimiter at the beginning of a line of C code unless it starts the body of a function. The most likely problem case is when you want an opening delimiter at the start of a line inside a string. To avoid trouble, put an escape character (`\', in C and Emacs Lisp, `/' in some other Lisp dialects) before the opening delimiter. It will not affect the contents of the string. The original Emacs found defuns by moving upward a level of parentheses until there were no more levels to go up. This always required scanning back to the beginning of the buffer, even for a small function. To speed up the operation, Emacs was changed to assume that any `(' (or other character assigned the syntactic class of opening-delimiter) at the left margin is the start of a defun. This heuristic is nearly always right and avoids the costly scan; however, it mandates the convention described above. File: emacs, Node: Grinding, Next: Matching, Prev: Defuns, Up: Programs Indentation for Programs ======================== The best way to keep a program properly indented ("ground") is to use Emacs to re-indent it as you change the program. Emacs has commands to indent properly either a single line, a specified number of lines, or all of the lines inside a single parenthetical grouping. * Menu: * Basic Indent:: * Multi-line Indent:: Commands to reindent many lines at once. * Lisp Indent:: Specifying how each Lisp function should be indented. * C Indent:: Choosing an indentation style for C code. File: emacs, Node: Basic Indent, Next: Multi-line Indent, Prev: Grinding, Up: Grinding Basic Program Indentation Commands ---------------------------------- `TAB' Adjust indentation of current line. `LFD' Equivalent to RET followed by TAB (`newline-and-indent'). The basic indentation command is TAB, which gives the current line the correct indentation as determined from the previous lines. The function that TAB runs depends on the major mode; it is `lisp-indent-line' in Lisp mode, `c-indent-line' in C mode, etc. These functions understand different syntaxes for different languages, but they all do about the same thing. TAB in any programming language major mode inserts or deletes whitespace at the beginning of the current line, independent of where point is in the line. If point is inside the whitespace at the beginning of the line, TAB leaves it at the end of that whitespace; otherwise, TAB leaves point fixed with respect to the characters around it. Use `C-q TAB' to insert a tab at point. When entering a large amount of new code, use LFD (`newline-and-indent'), which is equivalent to a RET followed by a TAB. LFD creates a blank line, then gives it the appropriate indentation. TAB indents the second and following lines of the body of a parenthetical grouping each under the preceding one; therefore, if you alter one line's indentation to be nonstandard, the lines below tend to follow it. This is the right behavior in cases where the standard result of TAB does not look good. Remember that Emacs assumes that an open-parenthesis, open-brace or other opening delimiter at the left margin (including the indentation routines) is the start of a function. You should therefore never have an opening delimiter in column zero that is not the beginning of a function, not even inside a string. This restriction is vital for making the indentation commands fast. *Note Defuns::, for more information on this behavior. File: emacs, Node: Multi-line Indent, Next: Lisp Indent, Prev: Basic Indent, Up: Grinding Indenting Several Lines ----------------------- Several commands are available to re-indent several lines of code which have been altered or moved to a different level in a list structure, `C-M-q' Re-indent all the lines within one list (`indent-sexp'). `C-u TAB' Shift an entire list rigidly sideways so that its first line is properly indented. `C-M-\' Re-indent all lines in the region (`indent-region'). To re-indent the contents of a single list, position point before the beginning of it and type `C-M-q'. This key is bound to `indent-sexp' in Lisp mode, `indent-c-exp' in C mode, and bound to other suitable functions in other modes. The indentation of the line the sexp starts on is not changed; therefore, only the relative indentation within the list, and not its position, is changed. To correct the position as well, type a TAB before `C-M-q'. If the relative indentation within a list is correct but the indentation of its beginning is not, go to the line on which the list begins and type `C-u TAB'. When you give TAB a numeric argument, it moves all the lines in the group, starting on the current line, sideways the same amount that the current line moves. The command does not move lines that start inside strings, or C preprocessor lines when in C mode. Another way to specify a range to be re-indented is with point and mark. The command `C-M-\' (`indent-region') applies TAB to every line whose first character is between point and mark. File: emacs, Node: Lisp Indent, Next: C Indent, Prev: Multi-line Indent, Up: Grinding Customizing Lisp Indentation ---------------------------- The indentation pattern for a Lisp expression can depend on the function called by the expression. For each Lisp function, you can choose among several predefined patterns of indentation, or define an arbitrary one with a Lisp program. The standard pattern of indentation is as follows: the second line of the expression is indented under the first argument, if that is on the same line as the beginning of the expression; otherwise, the second line is indented underneath the function name. Each following line is indented under the previous line whose nesting depth is the same. If the variable `lisp-indent-offset' is non-`nil', it overrides the usual indentation pattern for the second line of an expression, so that such lines are always indented `lisp-indent-offset' more columns than the containing list. Certain functions override the standard pattern. Functions whose names start with `def' always indent the second line by `lisp-body-indention' extra columns beyond the open-parenthesis starting the expression. Individual functions can override the standard pattern in various ways, according to the `lisp-indent-function' property of the function name. (Note: `lisp-indent-function' was formerly called `lisp-indent-hook'). There are four possibilities for this property: `nil' This is the same as no property; the standard indentation pattern is used. `defun' The pattern used for function names that start with `def' is used for this function also. a number, NUMBER The first NUMBER arguments of the function are "distinguished" arguments; the rest are considered the "body" of the expression. A line in the expression is indented according to whether the first argument on it is distinguished or not. If the argument is part of the body, the line is indented `lisp-body-indent' more columns than the open-parenthesis starting the containing expression. If the argument is distinguished and is either the first or second argument, it is indented twice that many extra columns. If the argument is distinguished and not the first or second argument, the standard pattern is followed for that line. a symbol, SYMBOL SYMBOL should be a function name; that function is called to calculate the indentation of a line within this expression. The function receives two arguments: STATE The value returned by `parse-partial-sexp' (a Lisp primitive for indentation and nesting computation) when it parses up to the beginning of this line. POS The position at which the line being indented begins. It should return either a number, which is the number of columns of indentation for that line, or a list whose first element is such a number. The difference between returning a number and returning a list is that a number says that all following lines at the same nesting level should be indented just like this one; a list says that following lines might call for different indentations. This makes a difference when the indentation is computed by `C-M-q'; if the value is a number, `C-M-q' need not recalculate indentation for the following lines until the end of the list. File: emacs, Node: C Indent, Prev: Lisp Indent, Up: Grinding Customizing C Indentation ------------------------- Two variables control which commands perform C indentation and when. If `c-auto-newline' is non-`nil', newlines are inserted both before and after braces that you insert, and after colons and semicolons. Correct C indentation is done on all the lines that are made this way. If `c-tab-always-indent' is non-`nil', the TAB command in C mode does indentation only if point is at the left margin or within the line's indentation. If there is non-whitespace to the left of point, TAB just inserts a tab character in the buffer. Normally, this variable is `nil', and TAB always reindents the current line. C does not have anything analogous to particular function names for which special forms of indentation are desirable. However, it has a different need for customization facilities: many different styles of C indentation are in common use. There are six variables you can set to control the style that Emacs C mode will use. `c-indent-level' Indentation of C statements within surrounding block. The surrounding block's indentation is the indentation of the line on which the open-brace appears. `c-continued-statement-offset' Extra indentation given to a substatement, such as the then-clause of an if or body of a while. `c-brace-offset' Extra indentation for lines that start with an open brace. `c-brace-imaginary-offset' An open brace following other text is treated as if it were this far to the right of the start of its line. `c-argdecl-indent' Indentation level of declarations of C function arguments. `c-label-offset' Extra indentation for a line that is a label, case, or default. The variable `c-indent-level' controls the indentation for C statements with respect to the surrounding block. In the example { foo (); the difference in indentation between the lines is `c-indent-level'. Its standard value is 2. If the open-brace beginning the compound statement is not at the beginning of its line, the `c-indent-level' is added to the indentation of the line, not the column of the open-brace. For example, if (losing) { do_this (); One popular indentation style is that which results from setting `c-indent-level' to 8 and putting open-braces at the end of a line in this way. Another popular style prefers to put the open-brace on a separate line. In fact, the value of the variable `c-brace-imaginary-offset' is also added to the indentation of such a statement. Normally this variable is zero. Think of this variable as the imaginary position of the open brace, relative to the first non-blank character on the line. By setting the variable to 4 and `c-indent-level' to 0, you can get this style: if (x == y) { do_it (); } When `c-indent-level' is zero, the statements inside most braces line up exactly under the open brace. An exception are braces in column zero, like those surrounding a function's body. The statements inside those braces are not placed at column zero. Instead, `c-brace-offset' and `c-continued-statement-offset' (see below) are added to produce a typical offset between brace levels, and the statements are indented that far. `c-continued-statement-offset' controls the extra indentation for a line that starts within a statement (but not within parentheses or brackets). These lines are usually statements inside other statements, like the then-clauses of `if' statements and the bodies of `while' statements. The `c-continued-statement-offset' parameter determines the difference in indentation between the two lines in if (x == y) do_it (); The default value for `c-continued-statement-offset' is 2. Some popular indentation styles correspond to a value of zero for `c-continued-statement-offset'. `c-brace-offset' is the extra indentation given to a line that starts with an open-brace. Its standard value is zero; compare if (x == y) { with if (x == y) do_it (); if you set `c-brace-offset' to 4, the first example becomes if (x == y) { `c-argdecl-indent' controls the indentation of declarations of the arguments of a C function. It is absolute: argument declarations receive exactly `c-argdecl-indent' spaces. The standard value is 5 and results in code like this: char * index (string, char) char *string; int char; `c-label-offset' is the extra indentation given to a line that contains a label, a case statement, or a `default:' statement. Its standard value is -2 and results in code like this switch (c) { case 'x': If `c-label-offset' were zero, the same code would be indented as switch (c) { case 'x': This example assumes that the other variables above also have their default values. Using the indentation style produced by the default settings of the variables just discussed, and putting open braces on separate lines produces clear and readable files. For an example, look at any of the C source files of GNU Emacs. File: emacs, Node: Matching, Next: Comments, Prev: Grinding, Up: Programs Automatic Display of Matching Parentheses ========================================= The Emacs parenthesis-matching feature shows you automatically how parentheses match in the text. Whenever a self-inserting character that is a closing delimiter is typed, the cursor moves momentarily to the location of the matching opening delimiter, provided that is visible on the screen. If it is not on the screen, some text starting with that opening delimiter is displayed in the echo area. Either way, you see the grouping you are closing off. In Lisp, automatic matching applies only to parentheses. In C, it also applies to braces and brackets. Emacs knows which characters to regard as matching delimiters based on the syntax table set by the major mode. *Note Syntax::. If the opening delimiter and closing delimiter are mismatched--such as in `[x)'--the echo area displays a warning message. The correct matches are specified in the syntax table. Two variables control parenthesis matching displays. `blink-matching-paren' turns the feature on or off: `nil' turns it off, but the default is `t' to turn match display on. `blink-matching-paren-distance' specifies how many characters back Emacs searches to find a matching opening delimiter. If the match is not found in the specified region, scanning stops, and nothing is displayed. This prevents wasting lots of time scanning when there is no match. The default is 4000.