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diff man/xemacs/programs.texi @ 0:376386a54a3c r19-14
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date | Mon, 13 Aug 2007 08:45:50 +0200 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/man/xemacs/programs.texi Mon Aug 13 08:45:50 2007 +0200 @@ -0,0 +1,1717 @@ + +@node Programs, Running, Text, Top +@chapter Editing Programs +@cindex Lisp +@cindex C + + Emacs has many commands designed to understand the syntax of programming +languages such as Lisp and C. These commands can: + +@itemize @bullet +@item +Move over or kill balanced expressions or @dfn{sexps} (@pxref{Lists}). +@item +Move over or mark top-level balanced expressions (@dfn{defuns}, in Lisp; +functions, in C). +@item +Show how parentheses balance (@pxref{Matching}). +@item +Insert, kill, or align comments (@pxref{Comments}). +@item +Follow the usual indentation conventions of the language +(@pxref{Grinding}). +@end itemize + + 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 (@pxref{Words}); sentences can +be found in strings and comments (@pxref{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 (@pxref{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 (@pxref{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. +* Asm Mode:: Asm mode and its special features. +@end menu + +@node Program Modes, Lists, Programs, Programs +@section Major Modes for Programming Languages + +@cindex Lisp mode +@cindex C mode +@cindex Scheme mode + 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. @xref{Lisp Modes}. + + Each of the programming language modes defines the @key{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 @key{TAB} is bound to @code{c-indent-line}. @key{LFD} +is normally defined to do @key{RET} followed by @key{TAB}; thus it, too, +indents in a mode-specific fashion. + +@kindex DEL +@findex backward-delete-char-untabify + In most programming languages, indentation is likely to vary from line to +line. So the major modes for those languages rebind @key{DEL} to treat a +tab as if it were the equivalent number of spaces (using the command +@code{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 @kbd{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. + +@cindex mode hook +@vindex c-mode-hook +@vindex lisp-mode-hook +@vindex emacs-lisp-mode-hook +@vindex lisp-interaction-mode-hook +@vindex scheme-mode-hook +@vindex muddle-mode-hook + Turning on a major mode calls a user-supplied function called the +@dfn{mode hook}, which is the value of a Lisp variable. For example, +turning on C mode calls the value of the variable @code{c-mode-hook} if +that value exists and is non-@code{nil}. Mode hook variables for other +programming language modes include @code{lisp-mode-hook}, +@code{emacs-lisp-mode-hook}, @code{lisp-interaction-mode-hook}, +@code{scheme-mode-hook}, and @code{muddle-mode-hook}. The mode hook +function receives no arguments.@refill + +@node Lists, Defuns, Program Modes, Programs +@section Lists and Sexps + +@cindex Control-Meta + By convention, Emacs keys for dealing with balanced expressions are +usually @kbd{Control-Meta-} characters. They tend to be analogous in +function to their @kbd{Control-} and @kbd{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). + +@cindex list +@cindex sexp +@cindex expression + The commands fall into two classes. Some commands deal only with +@dfn{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 @dfn{sexps}. The word `sexp' +is derived from @dfn{s-expression}, the term for a symbolic 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 @samp{foo + bar} as an sexp, even though it @i{is} a C expression; +it recognizes @samp{foo} as one sexp and @samp{bar} as another, with the +@samp{+} as punctuation between them. This is a fundamental ambiguity: +both @samp{foo + bar} and @samp{foo} are legitimate choices for the sexp to +move over if point is at the @samp{f}. Note that @samp{(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 doublewidecommands +@table @kbd +@item C-M-f +Move forward over an sexp (@code{forward-sexp}). +@item C-M-b +Move backward over an sexp (@code{backward-sexp}). +@item C-M-k +Kill sexp forward (@code{kill-sexp}). +@item C-M-u +Move up and backward in list structure (@code{backward-up-list}). +@item C-M-d +Move down and forward in list structure (@code{down-list}). +@item C-M-n +Move forward over a list (@code{forward-list}). +@item C-M-p +Move backward over a list (@code{backward-list}). +@item C-M-t +Transpose expressions (@code{transpose-sexps}). +@item C-M-@@ +Put mark after following expression (@code{mark-sexp}). +@end table + +@kindex C-M-f +@kindex C-M-b +@findex forward-sexp +@findex backward-sexp + To move forward over an sexp, use @kbd{C-M-f} (@code{forward-sexp}). If +the first significant character after point is an opening delimiter +(@samp{(} in Lisp; @samp{(}, @samp{[}, or @samp{@{} in C), @kbd{C-M-f} +moves past the matching closing delimiter. If the character begins a +symbol, string, or number, @kbd{C-M-f} moves over that. If the character +after point is a closing delimiter, @kbd{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 @kbd{C-M-f} because it is as useful a +behavior as anyone can think of for that situation.)@refill + + The command @kbd{C-M-b} (@code{backward-sexp}) moves backward over a +sexp. The detailed rules are like those above for @kbd{C-M-f}, but with +directions reversed. If there are any prefix characters (single quote, +back quote, and comma, in Lisp) preceding the sexp, @kbd{C-M-b} moves back +over them as well. + + @kbd{C-M-f} or @kbd{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. + +@kindex C-M-k +@findex kill-sexp + Killing an sexp at a time can be done with @kbd{C-M-k} (@code{kill-sexp}). +@kbd{C-M-k} kills the characters that @kbd{C-M-f} would move over. + +@kindex C-M-n +@kindex C-M-p +@findex forward-list +@findex backward-list + The @dfn{list commands}, @kbd{C-M-n} (@code{forward-list}) and +@kbd{C-M-p} (@code{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.@refill + +@kindex C-M-u +@kindex C-M-d +@findex backward-up-list +@findex down-list + @kbd{C-M-n} and @kbd{C-M-p} stay at the same level in parentheses, when +that is possible. To move @i{up} one (or @var{n}) levels, use @kbd{C-M-u} +(@code{backward-up-list}). +@kbd{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.@refill + + To move @i{down} in list structure, use @kbd{C-M-d} +(@code{down-list}). In Lisp mode, where @samp{(} is the only opening +delimiter, this is nearly the same as searching for a @samp{(}. An +argument specifies the number of levels of parentheses to go down. + +@cindex transposition +@kindex C-M-t +@findex transpose-sexps +@kbd{C-M-t} (@code{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 @kbd{C-M-t} with +a positive argument). An argument of zero, rather than doing nothing, +transposes the sexps ending after point and the mark. + +@kindex C-M-@@ +@findex mark-sexp + To make the region be the next sexp in the buffer, use @kbd{C-M-@@} +(@code{mark-sexp}) which sets the mark at the same place that +@kbd{C-M-f} would move to. @kbd{C-M-@@} takes arguments like +@kbd{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. +@xref{Syntax}. + +@node Defuns, Grinding, Lists, Programs +@section Defuns +@cindex defuns + + In Emacs, a parenthetical grouping at the top level in the buffer is +called a @dfn{defun}. The name derives from the fact that most +top-level lists in Lisp are instances of the special form +@code{defun}, but Emacs calls any top-level parenthetical +grouping counts a defun regardless of its contents or +the programming language. For example, in C, the body of a +function definition is a defun. + +@c doublewidecommands +@table @kbd +@item C-M-a +Move to beginning of current or preceding defun +(@code{beginning-of-defun}). +@item C-M-e +Move to end of current or following defun (@code{end-of-defun}). +@item C-M-h +Put region around whole current or following defun (@code{mark-defun}). +@end table + +@kindex C-M-a +@kindex C-M-e +@kindex C-M-h +@findex beginning-of-defun +@findex end-of-defun +@findex mark-defun + The commands to move to the beginning and end of the current defun are +@kbd{C-M-a} (@code{beginning-of-defun}) and @kbd{C-M-e} (@code{end-of-defun}). + + To operate on the current defun, use @kbd{C-M-h} (@code{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, @kbd{C-M-h} runs the function +@code{mark-c-function}, which is almost the same as @code{mark-defun}, +but which backs up over the argument declarations, function name, and +returned data type so that the entire C function is inside the region. + +@findex compile-defun +To compile and evaluate the current defun, use @kbd{M-x 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, @i{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 (@samp{\} in C +and Emacs Lisp, @samp{/} 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 +required scanning back to the beginning of the buffer for every +function. To speed this up, Emacs was changed to assume +that any @samp{(} (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; however, it mandates the convention +described above. + +@node Grinding, Matching, Defuns, Programs +@section Indentation for Programs +@cindex indentation +@cindex grinding + + 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. +@end menu + +@node Basic Indent, Multi-line Indent, Grinding, Grinding +@subsection Basic Program Indentation Commands + +@c WideCommands +@table @kbd +@item @key{TAB} +Adjust indentation of current line. +@item @key{LFD} +Equivalent to @key{RET} followed by @key{TAB} (@code{newline-and-indent}). +@end table + +@kindex TAB +@findex c-indent-line +@findex lisp-indent-line + The basic indentation command is @key{TAB}, which gives the current +line the correct indentation as determined from the previous lines. The +function that @key{TAB} runs depends on the major mode; it is +@code{lisp-indent-line} in Lisp mode, @code{c-indent-line} in C mode, +etc. These functions understand different syntaxes for different +languages, but they all do about the same thing. @key{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, +@key{TAB} leaves it at the end of that whitespace; otherwise, @key{TAB} +leaves point fixed with respect to the characters around it. + + Use @kbd{C-q @key{TAB}} to insert a tab at point. + +@kindex LFD +@findex newline-and-indent + When entering a large amount of new code, use @key{LFD} +(@code{newline-and-indent}), which is equivalent to a @key{RET} followed +by a @key{TAB}. @key{LFD} creates a blank line, then gives it the +appropriate indentation. + + @key{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 @key{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. @xref{Defuns}, for more +information on this behavior. + +@node Multi-line Indent, Lisp Indent, Basic Indent, Grinding +@subsection 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. + + +@table @kbd +@item C-M-q +Re-indent all the lines within one list (@code{indent-sexp}). +@item C-u @key{TAB} +Shift an entire list rigidly sideways so that its first line +is properly indented. +@item C-M-\ +Re-indent all lines in the region (@code{indent-region}). +@end table + +@kindex C-M-q +@findex indent-sexp +@findex indent-c-exp + To re-indent the contents of a single list, position point before the +beginning of it and type @kbd{C-M-q}. This key is bound to +@code{indent-sexp} in Lisp mode, @code{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 @key{TAB} before @kbd{C-M-q}. + +@kindex C-u TAB + 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 @kbd{C-u @key{TAB}}. When you give @key{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. + +@kindex C-M-\ +@findex indent-region + Another way to specify a range to be re-indented is with point and +mark. The command @kbd{C-M-\} (@code{indent-region}) applies @key{TAB} +to every line whose first character is between point and mark. + +@node Lisp Indent, C Indent, Multi-line Indent, Grinding +@subsection Customizing Lisp Indentation +@cindex customization + + 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. + +@vindex lisp-indent-offset + If the variable @code{lisp-indent-offset} is non-@code{nil}, it overrides +the usual indentation pattern for the second line of an expression, so that +such lines are always indented @code{lisp-indent-offset} more columns than +the containing list. + +@vindex lisp-body-indention + Certain functions override the standard pattern. Functions +whose names start with @code{def} always indent the second line by +@code{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 @code{lisp-indent-function} property of the +function name. (Note: @code{lisp-indent-function} was formerly called +@code{lisp-indent-hook}). There are four possibilities for this +property: + +@table @asis +@item @code{nil} +This is the same as no property; the standard indentation pattern is used. +@item @code{defun} +The pattern used for function names that start with @code{def} is used for +this function also. +@item a number, @var{number} +The first @var{number} arguments of the function are +@dfn{distinguished} arguments; the rest are considered the @dfn{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 @code{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 @i{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. +@item a symbol, @var{symbol} +@var{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: +@table @asis +@item @var{state} +The value returned by @code{parse-partial-sexp} (a Lisp primitive for +indentation and nesting computation) when it parses up to the +beginning of this line. +@item @var{pos} +The position at which the line being indented begins. +@end table +@noindent +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 @kbd{C-M-q}; if the value is a number, +@kbd{C-M-q} need not recalculate indentation for the following lines +until the end of the list. +@end table + +@node C Indent,, Lisp Indent, Grinding +@subsection Customizing C Indentation + + Two variables control which commands perform C indentation and when. + +@vindex c-auto-newline + If @code{c-auto-newline} is non-@code{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. + +@vindex c-tab-always-indent + If @code{c-tab-always-indent} is non-@code{nil}, the @key{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, +@key{TAB} just inserts a tab character in the buffer. Normally, +this variable is @code{nil}, and @key{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. + +@table @code +@item 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. +@item c-continued-statement-offset +Extra indentation given to a substatement, such as the then-clause of +an @code{if} or body of a @code{while}. +@item c-brace-offset +Extra indentation for lines that start with an open brace. +@item 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. +@item c-argdecl-indent +Indentation level of declarations of C function arguments. +@item c-label-offset +Extra indentation for a line that is a label, case, or default. +@end table + +@vindex c-indent-level + The variable @code{c-indent-level} controls the indentation for C +statements with respect to the surrounding block. In the example: + +@example + @{ + foo (); +@end example + +@noindent +the difference in indentation between the lines is @code{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 @code{c-indent-level} is added to the indentation of the +line, not the column of the open-brace. For example, + +@example +if (losing) @{ + do_this (); +@end example + +@noindent +One popular indentation style is that which results from setting +@code{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. + +@vindex c-brace-imaginary-offset + In fact, the value of the variable @code{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 @code{c-indent-level} to 0, you can get this style: + +@example +if (x == y) @{ + do_it (); + @} +@end example + + When @code{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, +@code{c-brace-offset} and @code{c-continued-statement-offset} (see +below) are added to produce a typical offset between brace levels, and +the statements are indented that far. + +@vindex c-continued-statement-offset + @code{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 @code{if} statements and the bodies of +@code{while} statements. The @code{c-continued-statement-offset} +parameter determines the difference in indentation between the two lines in: + +@example +if (x == y) + do_it (); +@end example + +@noindent +The default value for @code{c-continued-statement-offset} is 2. Some +popular indentation styles correspond to a value of zero for +@code{c-continued-statement-offset}. + +@vindex c-brace-offset + @code{c-brace-offset} is the extra indentation given to a line that +starts with an open-brace. Its standard value is zero; +compare: + +@example +if (x == y) + @{ +@end example + +@noindent +with: + +@example +if (x == y) + do_it (); +@end example + +@noindent +If you set @code{c-brace-offset} to 4, the first example becomes: + +@example +if (x == y) + @{ +@end example + +@vindex c-argdecl-indent + @code{c-argdecl-indent} controls the indentation of declarations of the +arguments of a C function. It is absolute: argument declarations receive +exactly @code{c-argdecl-indent} spaces. The standard value is 5 and +results in code like this: + +@example +char * +index (string, char) + char *string; + int char; +@end example + +@vindex c-label-offset + @code{c-label-offset} is the extra indentation given to a line that +contains a label, a case statement, or a @code{default:} statement. Its +standard value is @minus{}2 and results in code like this: + +@example +switch (c) + @{ + case 'x': +@end example + +@noindent +If @code{c-label-offset} were zero, the same code would be indented as: + +@example +switch (c) + @{ + case 'x': +@end example + +@noindent +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 XEmacs. + +@node Matching, Comments, Grinding, Programs +@section Automatic Display of Matching Parentheses +@cindex matching parentheses +@cindex 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. @xref{Syntax}. + + If the opening delimiter and closing delimiter are mismatched---as +in @samp{[x)}---the echo area displays a warning message. The +correct matches are specified in the syntax table. + +@vindex blink-matching-paren +@vindex blink-matching-paren-distance + Two variables control parenthesis matching displays. +@code{blink-matching-paren} turns the feature on or off. The default is +@code{t} (match display is on); @code{nil} turns it off. +@code{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. + +@node Comments, Balanced Editing, Matching, Programs +@section Manipulating Comments +@cindex comments +@kindex M-; +@cindex indentation +@findex indent-for-comment + + The comment commands insert, kill and align comments. + +@c WideCommands +@table @kbd +@item M-; +Insert or align comment (@code{indent-for-comment}). +@item C-x ; +Set comment column (@code{set-comment-column}). +@item C-u - C-x ; +Kill comment on current line (@code{kill-comment}). +@item M-@key{LFD} +Like @key{RET} followed by inserting and aligning a comment +(@code{indent-new-comment-line}). +@end table + + The command that creates a comment is @kbd{Meta-;} +(@code{indent-for-comment}). If there is no comment already on the +line, a new comment is created and aligned at a specific column called +the @dfn{comment column}. Emacs creates the comment by inserting the +string at the value of @code{comment-start}; see below. Point is left +after that string. If the text of the line extends past the comment +column, indentation is done to a suitable boundary (usually, at least +one space is inserted). If the major mode has specified a string to +terminate comments, that string is inserted after point, to keep the +syntax valid. + + You can also use @kbd{Meta-;} to align an existing comment. If a line +already contains the string that starts comments, @kbd{M-;} just moves +point after it and re-indents it to the conventional place. Exception: +comments starting in column 0 are not moved. + + 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 @key{TAB} +and by not changing the indentation of a triple-semicolon comment at all. + +@example +;; 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. +@end example + + In C code, a comment preceded on its line by nothing but whitespace +is indented like a line of code. + + Even when an existing comment is properly aligned, @kbd{M-;} is still +useful for moving directly to the start of the comment. + +@kindex C-u - C-x ; +@findex kill-comment + @kbd{C-u - C-x ;} (@code{kill-comment}) kills the comment on the +current line, if there is one. The indentation before the start of the +comment is killed as well. If there does not appear to be a comment in +the line, nothing happens. To reinsert the comment on another line, +move to the end of that line, type first @kbd{C-y}, and then @kbd{M-;} +to realign the comment. Note that @kbd{C-u - C-x ;} is not a distinct +key; it is @kbd{C-x ;} (@code{set-comment-column}) with a negative +argument. That command is programmed to call @code{kill-comment} when +called with a negative argument. However, @code{kill-comment} is a +valid command which you could bind directly to a key if you wanted to. + +@subsection Multiple Lines of Comments + +@kindex M-LFD +@cindex blank lines +@cindex Auto Fill mode +@findex indent-new-comment-line + If you are typing a comment and want to continue it on another line, +use the command @kbd{Meta-@key{LFD}} (@code{indent-new-comment-line}), +which terminates the comment you are typing, creates a new blank line +afterward, and begins a new comment indented under the old one. If +Auto Fill mode is on and you go past the fill column while typing, the +comment is continued in just this fashion. If point is +not at the end of the line when you type @kbd{M-@key{LFD}}, the text on +the rest of the line becomes part of the new comment line. + +@subsection Options Controlling Comments + +@vindex comment-column +@kindex C-x ; +@findex set-comment-column + The comment column is stored in the variable @code{comment-column}. You +can explicitly set it to a number. Alternatively, the command @kbd{C-x ;} +(@code{set-comment-column}) sets the comment column to the column point is +at. @kbd{C-u C-x ;} sets the comment column to match the last comment +before point in the buffer, and then calls @kbd{Meta-;} to align the +current line's comment under the previous one. Note that @kbd{C-u - C-x ;} +runs the function @code{kill-comment} as described above. + + @code{comment-column} is a per-buffer variable; altering the variable +affects only the current buffer. You can also change the default value. +@xref{Locals}. Many major modes initialize this variable +for the current buffer. + +@vindex comment-start-skip + The comment commands recognize comments based on the regular expression +that is the value of the variable @code{comment-start-skip}. This regexp +should 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 @code{@t{"/\\*+ *"}}, which matches extra +stars and spaces after the @samp{/*} itself. (Note that @samp{\\} is +needed in Lisp syntax to include a @samp{\} in the string, which is needed +to deny the first star its special meaning in regexp syntax. @xref{Regexps}.) + +@vindex comment-start +@vindex comment-end + When a comment command makes a new comment, it inserts the value of +@code{comment-start} to begin it. The value of @code{comment-end} is +inserted after point and will follow the text you will insert +into the comment. In C mode, @code{comment-start} has the value +@w{@code{"/* "}} and @code{comment-end} has the value @w{@code{" */"}}. + +@vindex comment-multi-line + @code{comment-multi-line} controls how @kbd{M-@key{LFD}} +(@code{indent-new-comment-line}) behaves when used inside a comment. If +@code{comment-multi-line} is @code{nil}, as it normally is, then +@kbd{M-@key{LFD}} terminates the comment on the starting line and starts +a new comment on the new following line. If @code{comment-multi-line} +is not @code{nil}, then @kbd{M-@key{LFD}} sets up the new following line +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 are legal, +the value you choose for this variable is a matter of taste. + +@vindex comment-indent-hook + The variable @code{comment-indent-hook} should contain a function that +is called to compute the indentation for a newly inserted comment or for +aligning an existing comment. Major modes set this variable differently. +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. The function should return the column in which the comment +ought to start. For example, in Lisp mode, the indent hook function +bases its decision on the number of semicolons that begin an existing +comment and on the code in the preceding lines. + +@node Balanced Editing, Lisp Completion, Comments, Programs +@section Editing Without Unbalanced Parentheses + +@table @kbd +@item M-( +Put parentheses around next sexp(s) (@code{insert-parentheses}). +@item M-) +Move past next close parenthesis and re-indent +(@code{move-over-close-and-reindent}). +@end table + +@kindex M-( +@kindex M-) +@findex insert-parentheses +@findex move-over-close-and-reindent + The commands @kbd{M-(} (@code{insert-parentheses}) and @kbd{M-)} +(@code{move-over-close-@*and-reindent}) are designed to facilitate a style of +editing which keeps parentheses balanced at all times. @kbd{M-(} inserts a +pair of parentheses, either together as in @samp{()}, or, if given an +argument, around the next several sexps, and leaves point after the open +parenthesis. Instead of typing @kbd{( F O O )}, you can type @kbd{M-( F O +O}, which has the same effect except for leaving the cursor before the +close parenthesis. You can then type @kbd{M-)}, which moves past the +close parenthesis, deletes any indentation preceding it (in this example +there is none), and indents with @key{LFD} after it. + +@node Lisp Completion, Documentation, Balanced Editing, Programs +@section Completion for Lisp Symbols +@cindex completion (symbol names) + + Completion usually happens in the minibuffer. An exception is +completion for Lisp symbol names, which is available in all buffers. + +@kindex M-TAB +@findex lisp-complete-symbol + The command @kbd{M-@key{TAB}} (@code{lisp-complete-symbol}) takes the +partial Lisp symbol before point to be an abbreviation, and compares it +against all non-trivial Lisp symbols currently known to Emacs. Any +additional characters that they all have in common are inserted at point. +Non-trivial symbols are those that have function definitions, values, or +properties. + + If there is an open-parenthesis immediately before the beginning of +the partial symbol, only symbols with function definitions are considered +as completions. + + If the partial name in the buffer has more than one possible completion +and they have no additional characters in common, a list of all possible +completions is displayed in another window. + +@node Documentation, Change Log, Lisp Completion, Programs +@section Documentation Commands + +@kindex C-h f +@findex describe-function +@kindex C-h v +@findex describe-variable + As you edit Lisp code to be run in Emacs, you can use the commands +@kbd{C-h f} (@code{describe-function}) and @kbd{C-h v} +(@code{describe-variable}) to print documentation of functions and +variables you want to call. These commands use the minibuffer to +read the name of a function or variable to document, and display the +documentation in a window. + + For extra convenience, these commands provide default arguments based on +the code in the neighborhood of point. @kbd{C-h f} sets the default to the +function called in the innermost list containing point. @kbd{C-h v} uses +the symbol name around or adjacent to point as its default. + +@findex manual-entry + The @kbd{M-x manual-entry} command gives you access to documentation +on Unix commands, system calls, and libraries. The command reads a +topic as an argument, and displays the Unix manual page for that topic. +@code{manual-entry} always searches all 8 sections of the +manual and concatenates all the entries it finds. For example, +the topic @samp{termcap} finds the description of the termcap library +from section 3, followed by the description of the termcap data base +from section 5. + +@node Change Log, Tags, Documentation, Programs +@section Change Logs + +@cindex change log +@findex add-change-log-entry + The Emacs command @kbd{M-x add-change-log-entry} helps you keep a record +of when and why you have changed a program. It assumes that you have a +file in which you write a chronological sequence of entries describing +individual changes. The default is to store the change entries in a file +called @file{ChangeLog} in the same directory as the file you are editing. +The same @file{ChangeLog} file therefore records changes for all the files +in a directory. + + A change log entry starts with a header line that contains your name +and the current date. Except for these header lines, every line in the +change log starts with a tab. One entry can describe several changes; +each change starts with a line starting with a tab and a star. @kbd{M-x +add-change-log-entry} visits the change log file and creates a new entry +unless the most recent entry is for today's date and your name. In +either case, it adds a new line to start the description of another +change just after the header line of the entry. When @kbd{M-x +add-change-log-entry} is finished, all is prepared for you to edit in +the description of what you changed and how. You must then save the +change log file yourself. + + The change log file is always visited in Indented Text mode, which means +that @key{LFD} and auto-filling indent each new line like the previous +line. This is convenient for entering the contents of an entry, which must +be indented. @xref{Text Mode}. + + Here is an example of the formatting conventions used in the change log +for Emacs: + +@smallexample +Wed Jun 26 19:29:32 1985 Richard M. Stallman (rms at mit-prep) + + * xdisp.c (try_window_id): + If C-k is done at end of next-to-last line, + this fn updates window_end_vpos and cannot leave + window_end_pos nonnegative (it is zero, in fact). + If display is preempted before lines are output, + this is inconsistent. Fix by setting + blank_end_of_window to nonzero. + +Tue Jun 25 05:25:33 1985 Richard M. Stallman (rms at mit-prep) + + * cmds.c (Fnewline): + Call the auto fill hook if appropriate. + + * xdisp.c (try_window_id): + If point is found by compute_motion after xp, record that + permanently. If display_text_line sets point position wrong + (case where line is killed, point is at eob and that line is + not displayed), set it again in final compute_motion. +@end smallexample + +@node Tags, Fortran, Change Log, Programs +@section Tag Tables +@cindex tag table + + A @dfn{tag table} is a description of how a multi-file program is +broken up into files. It lists the names of the component files and the +names and positions of the functions in each file. Grouping the related +files makes it possible to search or replace through all the files with +one command. Recording the function names and positions makes it +possible to use the @kbd{Meta-.} command, which finds the definition of a +function without asking for information on the file it is in. + + Tag tables are stored in files called @dfn{tag table files}. The +conventional name for a tag table file is @file{TAGS}. + + Each entry in the tag table records the name of one tag, the name of the +file that the tag is defined in (implicitly), and the position in that file +of the tag's definition. + + The programming language of a file determines what names are recorded +in the tag table depends on. Normally, Emacs includes all functions and +subroutines, and may also include global variables, data types, and +anything else convenient. Each recorded name is called a @dfn{tag}. + +@menu +* Tag Syntax:: +* Create Tag Table:: +* Select Tag Table:: +* Find Tag:: +* Tags Search:: +* Tags Stepping:: +* List Tags:: +@end menu + +@node Tag Syntax, Create Tag Table, Tags, Tags +@subsection Source File Tag Syntax + + In Lisp code, any function defined with @code{defun}, any variable +defined with @code{defvar} or @code{defconst}, and the first argument of +any expression that starts with @samp{(def} in column zero, is a tag. + + In C code, any C function is a tag, and so is any typedef if @code{-t} is +specified when the tag table is constructed. + + In Fortran code, functions and subroutines are tags. + + In La@TeX{} text, the argument of any of the commands @code{\chapter}, +@code{\section}, @code{\subsection}, @code{\subsubsection}, @code{\eqno}, +@code{\label}, @code{\ref}, @code{\cite}, @code{\bibitem}, and +@*@code{\typeout} is a tag.@refill + +@node Create Tag Table, Select Tag Table, Tag Syntax, Tags +@subsection Creating Tag Tables +@cindex etags program + + The @code{etags} program is used to create a tag table file. It knows +the syntax of C, Fortran, La@TeX{}, Scheme, and Emacs Lisp/Common Lisp. To +use @code{etags}, use it as a shell command: + +@example +etags @var{inputfiles}@dots{} +@end example +@noindent + +The program reads the specified files and writes a tag table +named @file{TAGS} in the current working directory. @code{etags} +recognizes the language used in an input file based on the name and +contents of the file; there are no switches for specifying the language. +The @code{-t} switch tells @code{etags} to record typedefs in C code as +tags. + + If the tag table data become outdated due to changes in the files +described in the table, you can update the tag table by running the +program from the shell again. It is not necessary to do this often. + + If the tag table fails to record a tag, or records it for the wrong file, +Emacs cannot find its definition. However, if the position +recorded in the tag table becomes a little bit wrong (due to some editing +in the file that the tag definition is in), the only consequence is to slow +down finding the tag slightly. Even if the stored position is very wrong, +Emacs will still find the tag, but it must search the entire file for it. + + You should update a tag table when you define new tags you want +to have listed, when you move tag definitions from one file to another, +or when changes become substantial. You don't have to update +the tag table after each edit, or even every day. + +@node Select Tag Table, Find Tag, Create Tag Table, Tags +@subsection Selecting a Tag Table + +@vindex tag-table-alist + At any time Emacs has one @dfn{selected} tag table, and all the commands +for working with tag tables use the selected one. To select a tag table, +use the variable @code{tag-table-alist}. + +The value of @code{tag-table-alist} is a list that determines which +@code{TAGS} files should be active for a given buffer. This is not +really an association list, in that all elements are checked. The car +of each element of this list is a pattern against which the buffers file +name is compared; if it matches, then the cdr of the list should be the +name of the tags table to use. If more than one element of this list +matches the buffers file name, all of the associated tags tables are +used. Earlier ones are searched first. + +If the car of elements of this list are strings, they are treated +as regular-expressions against which the file is compared (like the +@code{auto-mode-alist}). If they are not strings, they are evaluated. +If they evaluate to non-@code{nil}, the current buffer is considered to +match. + +If the cdr of the elements of this list are strings, they are +assumed to name a tags file. If they name a directory, the string +@file{tags} is appended to them to get the file name. If they are not +strings, they are evaluated and must return an appropriate string. + +For example: + +@example + (setq tag-table-alist + '(("/usr/src/public/perl/" . "/usr/src/public/perl/perl-3.0/") + ("\\.el$" . "/usr/local/emacs/src/") + ("/jbw/gnu/" . "/usr15/degree/stud/jbw/gnu/") + ("" . "/usr/local/emacs/src/") + )) +@end example + +The example defines the tag table alist in the following way: + +@itemize @bullet +@item +Anything in the directory @file{/usr/src/public/perl/} +should use the @file{TAGS} file @file{/usr/src/public/perl/perl-3.0/TAGS}. +@item +Files ending in @file{.el} should use the @file{TAGS} file +@file{/usr/local/emacs/src/TAGS}. +@item +Anything in or below the directory @file{/jbw/gnu/} should use the +@file{TAGS} file @file{/usr15/degree/stud/jbw/gnu/TAGS}. +@end itemize + +If you had a file called @file{/usr/jbw/foo.el}, it would use both +@file{TAGS} files, @* @file{/usr/local/emacs/src/TAGS} and +@file{/usr15/degree/stud/jbw/gnu/TAGS} (in that order), because it +matches both patterns. + +If the buffer-local variable @code{buffer-tag-table} is set, it names a +tags table that is searched before all others when @code{find-tag} is +executed from this buffer. + +If there is a file called @file{TAGS} in the same directory as the file +in question, then that tags file will always be used as well (after the +@code{buffer-tag-table} but before the tables specified by this list). + +If the variable @code{tags-file-name} is set, the @file{TAGS} file it names +will apply to all buffers (for backwards compatibility.) It is searched +first. + +@vindex tags-always-build-completion-table +If the value of the variable @code{tags-always-build-completion-table} +is @code{t}, the tags file will always be added to the completion table +without asking first, regardless of the size of the tags file. + +@vindex tags-file-name +@findex visit-tags-table +The function @kbd{M-x visit-tags-table}, is largely made obsolete by +the variable @code{tag-table-alist}, tells tags commands to use the tags +table file @var{file} first. The @var{file} should be the name of a +file created with the @code{etags} program. A directory name is also +acceptable; it means the file @file{TAGS} in that directory. The +function only stores the file name you provide in the variable +@code{tags-file-name}. Emacs does not actually read in the tag table +contents until you try to use them. You can set the variable explicitly +instead of using @code{visit-tags-table}. The value of the variable +@code{tags-file-name} is the name of the tags table used by all buffers. +This is for backward compatibility, and is largely supplanted by the +variable @code{tag-table-alist}. + +@node Find Tag, Tags Search, Select Tag Table, Tags +@subsection Finding a Tag + + The most important thing that a tag table enables you to do is to find +the definition of a specific tag. + +@table @kbd +@item M-.@: @var{tag &optional other-window} +Find first definition of @var{tag} (@code{find-tag}). +@item C-u M-. +Find next alternate definition of last tag specified. +@item C-x 4 . @var{tag} +Find first definition of @var{tag}, but display it in another window +(@code{find-tag-other-window}). +@end table + +@kindex M-. +@findex find-tag + @kbd{M-.}@: (@code{find-tag}) is the command to find the definition of +a specified tag. It searches through the tag table for that tag, as a +string, then uses the tag table information to determine the file in +which the definition is used and the approximate character position of +the definition in the file. Then @code{find-tag} visits the file, +moves point to the approximate character position, and starts searching +ever-increasing distances away for the text that should appear at +the beginning of the definition. + + If an empty argument is given (by typing @key{RET}), the sexp in the +buffer before or around point is used as the name of the tag to find. +@xref{Lists}, for information on sexps. + + The argument to @code{find-tag} need not be the whole tag name; it can +be a substring of a tag name. However, there can be many tag names +containing the substring you specify. Since @code{find-tag} works by +searching the text of the tag table, it finds the first tag in the table +that the specified substring appears in. To find other tags that match +the substring, give @code{find-tag} a numeric argument, as in @kbd{C-u +M-.}. This does not read a tag name, but continues searching the tag +table's text for another tag containing the same substring last used. +If your keyboard has a real @key{META} key, @kbd{M-0 M-.}@: is an easier +alternative to @kbd{C-u M-.}. + +If the optional second argument @var{other-window} is non-@code{nil}, it uses +another window to display the tag. +Multiple active tags tables and completion are supported. + +Variables of note include the following: + +@vindex tag-table-alist +@vindex tags-file-name +@vindex tags-build-completion-table +@vindex buffer-tag-table +@vindex make-tags-files-invisible +@vindex tag-mark-stack-max + +@table @kbd +@item tag-table-alist +Controls which tables apply to which buffers. +@item tags-file-name +Stores a default tags table. +@item tags-build-completion-table +Controls completion behavior. +@item buffer-tag-table +Specifies a buffer-local table. +@item make-tags-files-invisible +Sets whether tags tables should be very hidden. +@item tag-mark-stack-max +Specifies how many tags-based hops to remember. +@end table + +@kindex C-x 4 . +@findex find-tag-other-window + Like most commands that can switch buffers, @code{find-tag} has another +similar command that displays the new buffer in another window. @kbd{C-x 4 +.}@: invokes the function @code{find-tag-other-window}. (This key sequence +ends with a period.) + + Emacs comes with a tag table file @file{TAGS} (in the directory +containing Lisp libraries) that includes all the Lisp libraries and all +the C sources of Emacs. By specifying this file with @code{visit-tags-table} +and then using @kbd{M-.}@: you can quickly look at the source of any Emacs +function. + +@node Tags Search, Tags Stepping, Find Tag, Tags +@subsection Searching and Replacing with Tag Tables + + The commands in this section visit and search all the files listed in the +selected tag table, one by one. For these commands, the tag table serves +only to specify a sequence of files to search. A related command is +@kbd{M-x grep} (@pxref{Compilation}). + +@table @kbd +@item M-x tags-search +Search for the specified regexp through the files in the selected tag +table. +@item M-x tags-query-replace +Perform a @code{query-replace} on each file in the selected tag table. +@item M-, +Restart one of the commands above, from the current location of point +(@code{tags-loop-continue}). +@end table + +@findex tags-search + @kbd{M-x tags-search} reads a regexp using the minibuffer, then visits +the files of the selected tag table one by one, and searches through each +file for that regexp. It displays the name of the file being searched so +you can follow its progress. As soon as an occurrence is found, +@code{tags-search} returns. + +@kindex M-, +@findex tags-loop-continue + After you have found one match, you probably want to find all the rest. +To find one more match, type @kbd{M-,} (@code{tags-loop-continue}) to +resume the @code{tags-search}. This searches the rest of the current +buffer, followed by the remaining files of the tag table. + +@findex tags-query-replace + @kbd{M-x tags-query-replace} performs a single @code{query-replace} +through all the files in the tag table. It reads a string to search for +and a string to replace with, just like ordinary @kbd{M-x query-replace}. +It searches much like @kbd{M-x tags-search} but repeatedly, processing +matches according to your input. @xref{Replace}, for more information on +@code{query-replace}.@refill + + It is possible to get through all the files in the tag table with a +single invocation of @kbd{M-x tags-query-replace}. But since any +unrecognized character causes the command to exit, you may need to continue +from where you left off. You can use @kbd{M-,} to do this. It resumes +the last tags search or replace command that you did. + + It may have struck you that @code{tags-search} is a lot like @code{grep}. +You can also run @code{grep} itself as an inferior of Emacs and have Emacs +show you the matching lines one by one. This works mostly the same as +running a compilation and having Emacs show you where the errors were. +@xref{Compilation}. + +@node Tags Stepping, List Tags, Tags Search, Tags +@subsection Stepping Through a Tag Table +@findex next-file + + If you wish to process all the files in a selected tag table, but +@kbd{M-x tags-search} and @kbd{M-x tags-query-replace} are not giving +you the desired result, you can use @kbd{M-x next-file}. + +@table @kbd +@item C-u M-x next-file +With a numeric argument, regardless of its value, visit the first +file in the tag table and prepare to advance sequentially by files. +@item M-x next-file +Visit the next file in the selected tag table. +@end table + +@node List Tags,, Tags Stepping, Tags +@subsection Tag Table Inquiries + +@table @kbd +@item M-x list-tags +Display a list of the tags defined in a specific program file. +@item M-x tags-apropos +Display a list of all tags matching a specified regexp. +@end table + +@findex list-tags + @kbd{M-x list-tags} reads the name of one of the files described by the +selected tag table, and displays a list of all the tags defined in that +file. The ``file name'' argument is really just a string to compare +against the names recorded in the tag table; it is read as a string rather +than a file name. Therefore, completion and defaulting are not +available, and you must enter the string the same way it appears in the tag +table. Do not include a directory as part of the file name unless the file +name recorded in the tag table contains that directory. + +@findex tags-apropos + @kbd{M-x tags-apropos} is like @code{apropos} for tags. It reads a regexp, +then finds all the tags in the selected tag table whose entries match that +regexp, and displays the tag names found. + +@node Fortran, Asm Mode, Tags, Programs +@section Fortran Mode +@cindex Fortran mode + + Fortran mode provides special motion commands for Fortran statements and +subprograms, and indentation commands that understand Fortran conventions +of nesting, line numbers, and continuation statements. + + Special commands for comments are provided because Fortran comments are +unlike those of other languages. + + Built-in abbrevs optionally save typing when you insert Fortran keywords. + +@findex fortran-mode + Use @kbd{M-x fortran-mode} to switch to this major mode. Doing so calls +the value of @code{fortran-mode-hook} as a function of no arguments if +that variable has a non-@code{nil} value. + +@menu +* Motion: Fortran Motion. Moving point by statements or subprograms. +* Indent: Fortran Indent. Indentation commands for Fortran. +* Comments: Fortran Comments. Inserting and aligning comments. +* Columns: Fortran Columns. Measuring columns for valid Fortran. +* Abbrev: Fortran Abbrev. Built-in abbrevs for Fortran keywords. +@end menu + + Fortran mode was contributed by Michael Prange. + +@node Fortran Motion, Fortran Indent, Fortran, Fortran +@subsection Motion Commands + + Fortran mode provides special commands to move by subprograms (functions +and subroutines) and by statements. There is also a command to put the +region around one subprogram, which is convenient for killing it or moving it. + +@kindex C-M-a (Fortran mode) +@kindex C-M-e (Fortran mode) +@kindex C-M-h (Fortran mode) +@kindex C-c C-p (Fortran mode) +@kindex C-c C-n (Fortran mode) +@findex beginning-of-fortran-subprogram +@findex end-of-fortran-subprogram +@findex mark-fortran-subprogram +@findex fortran-previous-statement +@findex fortran-next-statement + +@table @kbd +@item C-M-a +Move to beginning of subprogram@* +(@code{beginning-of-fortran-subprogram}). +@item C-M-e +Move to end of subprogram (@code{end-of-fortran-subprogram}). +@item C-M-h +Put point at beginning of subprogram and mark at end +(@code{mark-fortran-subprogram}). +@item C-c C-n +Move to beginning of current or next statement +(@code{fortran-next-@*statement}). +@item C-c C-p +Move to beginning of current or previous statement +(@code{fortran-@*previous-statement}). +@end table + +@node Fortran Indent, Fortran Comments, Fortran Motion, Fortran +@subsection Fortran Indentation + + Special commands and features are available for indenting Fortran +code. They make sure various syntactic entities (line numbers, comment line +indicators, and continuation line flags) appear in the columns that are +required for standard Fortran. + +@menu +* Commands: ForIndent Commands. Commands for indenting Fortran. +* Numbers: ForIndent Num. How line numbers auto-indent. +* Conv: ForIndent Conv. Conventions you must obey to avoid trouble. +* Vars: ForIndent Vars. Variables controlling Fortran indent style. +@end menu + +@node ForIndent Commands, ForIndent Num, Fortran Indent, Fortran Indent +@subsubsection Fortran Indentation Commands + +@table @kbd +@item @key{TAB} +Indent the current line (@code{fortran-indent-line}). +@item M-@key{LFD} +Break the current line and set up a continuation line. +@item C-M-q +Indent all the lines of the subprogram point is in +(@code{fortran-indent-subprogram}). +@end table + +@findex fortran-indent-line + @key{TAB} is redefined by Fortran mode to reindent the current line for +Fortran (@code{fortran-indent-line}). Line numbers and continuation +markers are indented to their required columns, and the body of the +statement is independently indented, based on its nesting in the program. + +@kindex C-M-q (Fortran mode) +@findex fortran-indent-subprogram + The key @kbd{C-M-q} is redefined as @code{fortran-indent-subprogram}, a +command that reindents all the lines of the Fortran subprogram (function or +subroutine) containing point. + +@kindex M-LFD (Fortran mode) +@findex fortran-split-line + The key @kbd{M-@key{LFD}} is redefined as @code{fortran-split-line}, a +command to split a line in the appropriate fashion for Fortran. In a +non-comment line, the second half becomes a continuation line and is +indented accordingly. In a comment line, both halves become separate +comment lines. + +@node ForIndent Num, ForIndent Conv, ForIndent Commands, Fortran Indent +@subsubsection Line Numbers and Continuation + + If a number is the first non-whitespace in the line, it is assumed to be +a line number and is moved to columns 0 through 4. (Columns are always +counted from 0 in XEmacs.) If the text on the line starts with the +conventional Fortran continuation marker @samp{$}, it is moved to column 5. +If the text begins with any non whitespace character in column 5, it is +assumed to be an unconventional continuation marker and remains in column +5. + +@vindex fortran-line-number-indent + Line numbers of four digits or less are normally indented one space. +This amount is controlled by the variable @code{fortran-line-number-indent}, +which is the maximum indentation a line number can have. Line numbers +are indented to right-justify them to end in column 4 unless that would +require more than the maximum indentation. The default value of the +variable is 1. + +@vindex fortran-electric-line-number + Simply inserting a line number is enough to indent it according to these +rules. As each digit is inserted, the indentation is recomputed. To turn +off this feature, set the variable @code{fortran-electric-line-number} to +@code{nil}. Then inserting line numbers is like inserting anything else. + +@node ForIndent Conv, ForIndent Vars, ForIndent Num, Fortran Indent +@subsubsection Syntactic Conventions + + Fortran mode assumes that you follow certain conventions that simplify +the task of understanding a Fortran program well enough to indent it +properly: + +@vindex fortran-continuation-char +@itemize @bullet +@item +Two nested @samp{do} loops never share a @samp{continue} statement. + +@item +The same character appears in column 5 of all continuation lines. It +is the value of the variable @code{fortran-continuation-char}. +By default, this character is @samp{$}. +@end itemize + +@noindent +If you fail to follow these conventions, the indentation commands may +indent some lines unaesthetically. However, a correct Fortran program will +retain its meaning when reindented even if the conventions are not +followed. + +@node ForIndent Vars,, ForIndent Conv, Fortran Indent +@subsubsection Variables for Fortran Indentation + +@vindex fortran-do-indent +@vindex fortran-if-indent +@vindex fortran-continuation-indent +@vindex fortran-check-all-num-for-matching-do +@vindex fortran-minimum-statement-indent + Several additional variables control how Fortran indentation works. + +@table @code +@item fortran-do-indent +Extra indentation within each level of @samp{do} statement (the default is 3). + +@item fortran-if-indent +Extra indentation within each level of @samp{if} statement (the default is 3). + +@item fortran-continuation-indent +Extra indentation for bodies of continuation lines (the default is 5). + +@item fortran-check-all-num-for-matching-do +If this is @code{nil}, indentation assumes that each @samp{do} +statement ends on a @samp{continue} statement. Therefore, when +computing indentation for a statement other than @samp{continue}, it +can save time by not checking for a @samp{do} statement ending there. +If this is non-@code{nil}, indenting any numbered statement must check +for a @samp{do} that ends there. The default is @code{nil}. + +@item fortran-minimum-statement-indent +Minimum indentation for Fortran statements. For standard Fortran, +this is 6. Statement bodies are always indented at least this much. +@end table + +@node Fortran Comments, Fortran Columns, Fortran Indent, Fortran +@subsection Comments + + The usual Emacs comment commands assume that a comment can follow a line +of code. In Fortran, the standard comment syntax requires an entire line +to be just a comment. Therefore, Fortran mode replaces the standard Emacs +comment commands and defines some new variables. + + Fortran mode can also handle a non-standard comment syntax where comments +start with @samp{!} and can follow other text. Because only some Fortran +compilers accept this syntax, Fortran mode will not insert such comments +unless you have specified to do so in advance by setting the variable +@code{comment-start} to @samp{"!"} (@pxref{Variables}). + +@table @kbd +@item M-; +Align comment or insert new comment (@code{fortran-comment-indent}). + +@item C-x ; +Applies to nonstandard @samp{!} comments only. + +@item C-c ; +Turn all lines of the region into comments, or (with arg) +turn them back into real code (@code{fortran-comment-region}). +@end table + + @kbd{M-;} in Fortran mode is redefined as the command +@code{fortran-comment-indent}. Like the usual @kbd{M-;} command, +it recognizes an existing comment and aligns its text appropriately. +If there is no existing comment, a comment is inserted and aligned. + +Inserting and aligning comments is not the same in Fortran mode as in +other modes. When a new comment must be inserted, a full-line comment is +inserted if the current line is blank. On a non-blank line, a +non-standard @samp{!} comment is inserted if you previously specified +you wanted to use them. Otherwise a full-line comment is inserted on a +new line before the current line. + + Non-standard @samp{!} comments are aligned like comments in other +languages, but full-line comments are aligned differently. In a +standard full-line comment, the comment delimiter itself must always +appear in column zero. What can be aligned is the text within the +comment. You can choose from three styles of alignment by setting the +variable @code{fortran-comment-indent-style} to one of these values: + +@vindex fortran-comment-indent-style +@vindex fortran-comment-line-column +@table @code +@item fixed +The text is aligned at a fixed column, which is the value of +@code{fortran-comment-line-column}. This is the default. +@item relative +The text is aligned as if it were a line of code, but with an +additional @code{fortran-comment-line-column} columns of indentation. +@item nil +Text in full-line columns is not moved automatically. +@end table + +@vindex fortran-comment-indent-char + You can also specify the character to be used to indent within +full-line comments by setting the variable @code{fortran-comment-indent-char} +to the character you want to use. + +@vindex comment-line-start +@vindex comment-line-start-skip + Fortran mode introduces two variables @code{comment-line-start} and +@code{comment-line-start-skip}, which do for full-line comments what +@code{comment-start} and @code{comment-start-skip} do for +ordinary text-following comments. Normally these are set properly by +Fortran mode, so you do not need to change them. + + The normal Emacs comment command @kbd{C-x ;} has not been redefined. +It can therefore be used if you use @samp{!} comments, but is useless in +Fortran mode otherwise. + +@kindex C-c ; (Fortran mode) +@findex fortran-comment-region +@vindex fortran-comment-region + The command @kbd{C-c ;} (@code{fortran-comment-region}) turns all the +lines of the region into comments by inserting the string @samp{C$$$} at +the front of each one. With a numeric arg, the region is turned back into +live code by deleting @samp{C$$$} from the front of each line. You can +control the string used for the comments by setting the variable +@code{fortran-comment-region}. Note that here we have an example of a +command and a variable with the same name; the two uses of the name never +conflict because in Lisp and in Emacs it is always clear from the context +which one is referred to. + +@node Fortran Columns, Fortran Abbrev, Fortran Comments, Fortran +@subsection Columns + +@table @kbd +@item C-c C-r +Displays a ``column ruler'' momentarily above the current line +(@code{fortran-column-ruler}). +@item C-c C-w +Splits the current window horizontally so that it is 72 columns wide. +This may help you avoid going over that limit (@code{fortran-window-create}). +@end table + +@kindex C-c C-r (Fortran mode) +@findex fortran-column-ruler + The command @kbd{C-c C-r} (@code{fortran-column-ruler}) shows a column +ruler above the current line. The comment ruler consists of two lines +of text that show you the locations of columns with special significance +in Fortran programs. Square brackets show the limits of the columns for +line numbers, and curly brackets show the limits of the columns for the +statement body. Column numbers appear above them. + + Note that the column numbers count from zero, as always in XEmacs. As +a result, the numbers may not be those you are familiar with; but the +actual positions in the line are standard Fortran. + + The text used to display the column ruler is the value of the variable +@code{fortran-comment-ruler}. By changing this variable, you can change +the display. + +@kindex C-c C-w (Fortran mode) +@findex fortran-window-create + For even more help, use @kbd{C-c C-w} (@code{fortran-window-create}), a +command which splits the current window horizontally, resulting in a window 72 +columns wide. When you edit in this window, you can immediately see +when a line gets too wide to be correct Fortran. + +@node Fortran Abbrev,, Fortran Columns, Fortran +@subsection Fortran Keyword Abbrevs + + Fortran mode provides many built-in abbrevs for common keywords and +declarations. These are the same sort of abbrevs that you can define +yourself. To use them, you must turn on Abbrev mode. @pxref{Abbrevs}. + + The built-in abbrevs are unusual in one way: they all start with a +semicolon. You cannot normally use semicolon in an abbrev, but Fortran +mode makes this possible by changing the syntax of semicolon to ``word +constituent''. + + For example, one built-in Fortran abbrev is @samp{;c} for +@samp{continue}. If you insert @samp{;c} and then insert a punctuation +character such as a space or a newline, the @samp{;c} changes +automatically to @samp{continue}, provided Abbrev mode is enabled.@refill + + Type @samp{;?} or @samp{;C-h} to display a list of all built-in +Fortran abbrevs and what they stand for. + +@node Asm Mode,, Fortran, Programs +@section Asm Mode + +@cindex Asm mode +Asm mode is a major mode for editing files of assembler code. It +defines these commands: + +@table @kbd +@item @key{TAB} +@code{tab-to-tab-stop}. +@item @key{LFD} +Insert a newline and then indent using @code{tab-to-tab-stop}. +@item : +Insert a colon and then remove the indentation from before the label +preceding colon. Then do @code{tab-to-tab-stop}. +@item ; +Insert or align a comment. +@end table + + The variable @code{asm-comment-char} specifies which character +starts comments in assembler syntax.