X-Git-Url: http://git.hcoop.net/bpt/emacs.git/blobdiff_plain/7015aca4520d036305770c96f7ffbb8428b79ff0..3cd2b59fc8ea1e250ca865c39d543d59a23bffc7:/lispref/searching.texi diff --git a/lispref/searching.texi b/lispref/searching.texi index 28625c25bd..204cfa1d31 100644 --- a/lispref/searching.texi +++ b/lispref/searching.texi @@ -1,9 +1,10 @@ @c -*-texinfo-*- @c This is part of the GNU Emacs Lisp Reference Manual. -@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. +@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003, +@c 2004, 2005, 2006 Free Software Foundation, Inc. @c See the file elisp.texi for copying conditions. @setfilename ../info/searching -@node Searching and Matching, Syntax Tables, Text, Top +@node Searching and Matching, Syntax Tables, Non-ASCII Characters, Top @chapter Searching and Matching @cindex searching @@ -15,17 +16,19 @@ portions of it. @menu * String Search:: Search for an exact match. +* Searching and Case:: Case-independent or case-significant searching. * Regular Expressions:: Describing classes of strings. * Regexp Search:: Searching for a match for a regexp. -* Search and Replace:: Internals of @code{query-replace}. -* Match Data:: Finding out which part of the text matched - various parts of a regexp, after regexp search. -* Searching and Case:: Case-independent or case-significant searching. +* POSIX Regexps:: Searching POSIX-style for the longest match. +* Match Data:: Finding out which part of the text matched, + after a string or regexp search. +* Search and Replace:: Commands that loop, searching and replacing. * Standard Regexps:: Useful regexps for finding sentences, pages,... @end menu The @samp{skip-chars@dots{}} functions also perform a kind of searching. -@xref{Skipping Characters}. +@xref{Skipping Characters}. To search for changes in character +properties, see @ref{Property Search}. @node String Search @section Searching for Strings @@ -33,18 +36,22 @@ portions of it. These are the primitive functions for searching through the text in a buffer. They are meant for use in programs, but you may call them -interactively. If you do so, they prompt for the search string; -@var{limit} and @var{noerror} are set to @code{nil}, and @var{repeat} -is set to 1. +interactively. If you do so, they prompt for the search string; the +arguments @var{limit} and @var{noerror} are @code{nil}, and @var{repeat} +is 1. + + These search functions convert the search string to multibyte if the +buffer is multibyte; they convert the search string to unibyte if the +buffer is unibyte. @xref{Text Representations}. @deffn Command search-forward string &optional limit noerror repeat - This function searches forward from point for an exact match for +This function searches forward from point for an exact match for @var{string}. If successful, it sets point to the end of the occurrence found, and returns the new value of point. If no match is found, the value and side effects depend on @var{noerror} (see below). @c Emacs 19 feature - In the following example, point is initially at the beginning of the +In the following example, point is initially at the beginning of the line. Then @code{(search-forward "fox")} moves point after the last letter of @samp{fox}: @@ -65,23 +72,31 @@ The quick brown fox@point{} jumped over the lazy dog. @end group @end example - The argument @var{limit} specifies the upper bound to the search. (It +The argument @var{limit} specifies the upper bound to the search. (It must be a position in the current buffer.) No match extending after that position is accepted. If @var{limit} is omitted or @code{nil}, it defaults to the end of the accessible portion of the buffer. @kindex search-failed - What happens when the search fails depends on the value of +What happens when the search fails depends on the value of @var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed} error is signaled. If @var{noerror} is @code{t}, @code{search-forward} returns @code{nil} and does nothing. If @var{noerror} is neither @code{nil} nor @code{t}, then @code{search-forward} moves point to the -upper bound and returns @code{nil}. (It would be more consistent now -to return the new position of point in that case, but some programs -may depend on a value of @code{nil}.) +upper bound and returns @code{nil}. (It would be more consistent now to +return the new position of point in that case, but some existing +programs may depend on a value of @code{nil}.) - If @var{repeat} is non-@code{nil}, then the search is repeated that -many times. Point is positioned at the end of the last match. +The argument @var{noerror} only affects valid searches which fail to +find a match. Invalid arguments cause errors regardless of +@var{noerror}. + +If @var{repeat} is supplied (it must be a positive number), then the +search is repeated that many times (each time starting at the end of the +previous time's match). If these successive searches succeed, the +function succeeds, moving point and returning its new value. Otherwise +the search fails, with results depending on the value of +@var{noerror}, as described above. @end deffn @deffn Command search-backward string &optional limit noerror repeat @@ -126,15 +141,15 @@ the ball boy@point{}!" @end group @end example -If @var{limit} is non-@code{nil} (it must be a position in the current -buffer), then it is the upper bound to the search. The match found must -not extend after that position. +If @var{limit} is non-@code{nil}, it must be a position in the current +buffer; it specifies the upper bound to the search. The match found +must not extend after that position. If @var{noerror} is @code{nil}, then @code{word-search-forward} signals an error if the search fails. If @var{noerror} is @code{t}, then it returns @code{nil} instead of signaling an error. If @var{noerror} is neither @code{nil} nor @code{t}, it moves point to @var{limit} (or the -end of the buffer) and returns @code{nil}. +end of the accessible portion of the buffer) and returns @code{nil}. If @var{repeat} is non-@code{nil}, then the search is repeated that many times. Point is positioned at the end of the last match. @@ -147,6 +162,53 @@ except that it searches backward and normally leaves point at the beginning of the match. @end deffn +@node Searching and Case +@section Searching and Case +@cindex searching and case + + By default, searches in Emacs ignore the case of the text they are +searching through; if you specify searching for @samp{FOO}, then +@samp{Foo} or @samp{foo} is also considered a match. This applies to +regular expressions, too; thus, @samp{[aB]} would match @samp{a} or +@samp{A} or @samp{b} or @samp{B}. + + If you do not want this feature, set the variable +@code{case-fold-search} to @code{nil}. Then all letters must match +exactly, including case. This is a buffer-local variable; altering the +variable affects only the current buffer. (@xref{Intro to +Buffer-Local}.) Alternatively, you may change the value of +@code{default-case-fold-search}, which is the default value of +@code{case-fold-search} for buffers that do not override it. + + Note that the user-level incremental search feature handles case +distinctions differently. When given a lower case letter, it looks for +a match of either case, but when given an upper case letter, it looks +for an upper case letter only. But this has nothing to do with the +searching functions used in Lisp code. + +@defopt case-replace +This variable determines whether the higher level replacement +functions should preserve case. If the variable is @code{nil}, that +means to use the replacement text verbatim. A non-@code{nil} value +means to convert the case of the replacement text according to the +text being replaced. + +This variable is used by passing it as an argument to the function +@code{replace-match}. @xref{Replacing Match}. +@end defopt + +@defopt case-fold-search +This buffer-local variable determines whether searches should ignore +case. If the variable is @code{nil} they do not ignore case; otherwise +they do ignore case. +@end defopt + +@defvar default-case-fold-search +The value of this variable is the default value for +@code{case-fold-search} in buffers that do not override it. This is the +same as @code{(default-value 'case-fold-search)}. +@end defvar + @node Regular Expressions @section Regular Expressions @cindex regular expression @@ -157,157 +219,248 @@ denotes a (possibly infinite) set of strings. Searching for matches for a regexp is a very powerful operation. This section explains how to write regexps; the following section says how to search for them. +@findex re-builder +@cindex authoring regular expressions + For convenient interactive development of regular expressions, you +can use the @kbd{M-x re-builder} command. It provides a convenient +interface for creating regular expressions, by giving immediate visual +feedback in a separate buffer. As you edit the regexp, all its +matches in the target buffer are highlighted. Each parenthesized +sub-expression of the regexp is shown in a distinct face, which makes +it easier to verify even very complex regexps. + @menu * Syntax of Regexps:: Rules for writing regular expressions. * Regexp Example:: Illustrates regular expression syntax. +* Regexp Functions:: Functions for operating on regular expressions. @end menu @node Syntax of Regexps @subsection Syntax of Regular Expressions - Regular expressions have a syntax in which a few characters are special -constructs and the rest are @dfn{ordinary}. An ordinary character is a -simple regular expression which matches that character and nothing else. -The special characters are @samp{$}, @samp{^}, @samp{.}, @samp{*}, -@samp{+}, @samp{?}, @samp{[}, @samp{]} and @samp{\}; no new special -characters will be defined in the future. Any other character appearing -in a regular expression is ordinary, unless a @samp{\} precedes it. - -For example, @samp{f} is not a special character, so it is ordinary, and + Regular expressions have a syntax in which a few characters are +special constructs and the rest are @dfn{ordinary}. An ordinary +character is a simple regular expression that matches that character +and nothing else. The special characters are @samp{.}, @samp{*}, +@samp{+}, @samp{?}, @samp{[}, @samp{^}, @samp{$}, and @samp{\}; no new +special characters will be defined in the future. The character +@samp{]} is special if it ends a character alternative (see later). +The character @samp{-} is special inside a character alternative. A +@samp{[:} and balancing @samp{:]} enclose a character class inside a +character alternative. Any other character appearing in a regular +expression is ordinary, unless a @samp{\} precedes it. + + For example, @samp{f} is not a special character, so it is ordinary, and therefore @samp{f} is a regular expression that matches the string @samp{f} and no other string. (It does @emph{not} match the string -@samp{ff}.) Likewise, @samp{o} is a regular expression that matches -only @samp{o}.@refill +@samp{fg}, but it does match a @emph{part} of that string.) Likewise, +@samp{o} is a regular expression that matches only @samp{o}.@refill -Any two regular expressions @var{a} and @var{b} can be concatenated. The -result is a regular expression which matches a string if @var{a} matches + Any two regular expressions @var{a} and @var{b} can be concatenated. The +result is a regular expression that matches a string if @var{a} matches some amount of the beginning of that string and @var{b} matches the rest of the string.@refill -As a simple example, we can concatenate the regular expressions @samp{f} + As a simple example, we can concatenate the regular expressions @samp{f} and @samp{o} to get the regular expression @samp{fo}, which matches only the string @samp{fo}. Still trivial. To do something more powerful, you -need to use one of the special characters. Here is a list of them: +need to use one of the special regular expression constructs. + +@menu +* Regexp Special:: Special characters in regular expressions. +* Char Classes:: Character classes used in regular expressions. +* Regexp Backslash:: Backslash-sequences in regular expressions. +@end menu + +@node Regexp Special +@subsubsection Special Characters in Regular Expressions -@need 1200 -@table @kbd -@item .@: @r{(Period)} + Here is a list of the characters that are special in a regular +expression. + +@need 800 +@table @asis +@item @samp{.}@: @r{(Period)} @cindex @samp{.} in regexp is a special character that matches any single character except a newline. Using concatenation, we can make regular expressions like @samp{a.b}, which matches any three-character string that begins with @samp{a} and ends with @samp{b}.@refill -@item * +@item @samp{*} @cindex @samp{*} in regexp -is not a construct by itself; it is a suffix operator that means to -repeat the preceding regular expression as many times as possible. In -@samp{fo*}, the @samp{*} applies to the @samp{o}, so @samp{fo*} matches -one @samp{f} followed by any number of @samp{o}s. The case of zero -@samp{o}s is allowed: @samp{fo*} does match @samp{f}.@refill +is not a construct by itself; it is a postfix operator that means to +match the preceding regular expression repetitively as many times as +possible. Thus, @samp{o*} matches any number of @samp{o}s (including no +@samp{o}s). @samp{*} always applies to the @emph{smallest} possible preceding -expression. Thus, @samp{fo*} has a repeating @samp{o}, not a -repeating @samp{fo}.@refill - -The matcher processes a @samp{*} construct by matching, immediately, -as many repetitions as can be found. Then it continues with the rest -of the pattern. If that fails, backtracking occurs, discarding some -of the matches of the @samp{*}-modified construct in case that makes -it possible to match the rest of the pattern. For example, in matching -@samp{ca*ar} against the string @samp{caaar}, the @samp{a*} first -tries to match all three @samp{a}s; but the rest of the pattern is +expression. Thus, @samp{fo*} has a repeating @samp{o}, not a repeating +@samp{fo}. It matches @samp{f}, @samp{fo}, @samp{foo}, and so on. + +The matcher processes a @samp{*} construct by matching, immediately, as +many repetitions as can be found. Then it continues with the rest of +the pattern. If that fails, backtracking occurs, discarding some of the +matches of the @samp{*}-modified construct in the hope that that will +make it possible to match the rest of the pattern. For example, in +matching @samp{ca*ar} against the string @samp{caaar}, the @samp{a*} +first tries to match all three @samp{a}s; but the rest of the pattern is @samp{ar} and there is only @samp{r} left to match, so this try fails. -The next alternative is for @samp{a*} to match only two @samp{a}s. -With this choice, the rest of the regexp matches successfully.@refill - -@item + +The next alternative is for @samp{a*} to match only two @samp{a}s. With +this choice, the rest of the regexp matches successfully. + +@strong{Warning:} Nested repetition operators take a long time, +or even forever, if they +lead to ambiguous matching. For example, trying to match the regular +expression @samp{\(x+y*\)*a} against the string +@samp{xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxz} could take hours before it +ultimately fails. Emacs must try each way of grouping the 35 +@samp{x}s before concluding that none of them can work. Even worse, +@samp{\(x*\)*} can match the null string in infinitely many ways, so +it causes an infinite loop. To avoid these problems, check nested +repetitions carefully, to make sure that they do not cause combinatorial +explosions in backtracking. + +@item @samp{+} @cindex @samp{+} in regexp -is a suffix operator similar to @samp{*} except that the preceding -expression must match at least once. So, for example, @samp{ca+r} +is a postfix operator, similar to @samp{*} except that it must match +the preceding expression at least once. So, for example, @samp{ca+r} matches the strings @samp{car} and @samp{caaaar} but not the string @samp{cr}, whereas @samp{ca*r} matches all three strings. -@item ? +@item @samp{?} @cindex @samp{?} in regexp -is a suffix operator similar to @samp{*} except that the preceding -expression can match either once or not at all. For example, -@samp{ca?r} matches @samp{car} or @samp{cr}, but does not match anyhing -else. - -@item [ @dots{} ] -@cindex character set (in regexp) +is a postfix operator, similar to @samp{*} except that it must match the +preceding expression either once or not at all. For example, +@samp{ca?r} matches @samp{car} or @samp{cr}; nothing else. + +@item @samp{*?}, @samp{+?}, @samp{??} +These are ``non-greedy'' variants of the operators @samp{*}, @samp{+} +and @samp{?}. Where those operators match the largest possible +substring (consistent with matching the entire containing expression), +the non-greedy variants match the smallest possible substring +(consistent with matching the entire containing expression). + +For example, the regular expression @samp{c[ad]*a} when applied to the +string @samp{cdaaada} matches the whole string; but the regular +expression @samp{c[ad]*?a}, applied to that same string, matches just +@samp{cda}. (The smallest possible match here for @samp{[ad]*?} that +permits the whole expression to match is @samp{d}.) + +@item @samp{[ @dots{} ]} +@cindex character alternative (in regexp) @cindex @samp{[} in regexp @cindex @samp{]} in regexp -@samp{[} begins a @dfn{character set}, which is terminated by a -@samp{]}. In the simplest case, the characters between the two brackets -form the set. Thus, @samp{[ad]} matches either one @samp{a} or one -@samp{d}, and @samp{[ad]*} matches any string composed of just @samp{a}s -and @samp{d}s (including the empty string), from which it follows that -@samp{c[ad]*r} matches @samp{cr}, @samp{car}, @samp{cdr}, -@samp{caddaar}, etc.@refill - -The usual regular expression special characters are not special inside a -character set. A completely different set of special characters exists -inside character sets: @samp{]}, @samp{-} and @samp{^}.@refill - -@samp{-} is used for ranges of characters. To write a range, write two -characters with a @samp{-} between them. Thus, @samp{[a-z]} matches any -lower case letter. Ranges may be intermixed freely with individual -characters, as in @samp{[a-z$%.]}, which matches any lower case letter -or @samp{$}, @samp{%} or a period.@refill - -To include a @samp{]} in a character set, make it the first character. -For example, @samp{[]a]} matches @samp{]} or @samp{a}. To include a -@samp{-}, write @samp{-} as the first character in the set, or put -immediately after a range. (You can replace one individual character -@var{c} with the range @samp{@var{c}-@var{c}} to make a place to put the -@samp{-}). There is no way to write a set containing just @samp{-} and -@samp{]}. - -To include @samp{^} in a set, put it anywhere but at the beginning of -the set. - -@item [^ @dots{} ] +is a @dfn{character alternative}, which begins with @samp{[} and is +terminated by @samp{]}. In the simplest case, the characters between +the two brackets are what this character alternative can match. + +Thus, @samp{[ad]} matches either one @samp{a} or one @samp{d}, and +@samp{[ad]*} matches any string composed of just @samp{a}s and @samp{d}s +(including the empty string), from which it follows that @samp{c[ad]*r} +matches @samp{cr}, @samp{car}, @samp{cdr}, @samp{caddaar}, etc. + +You can also include character ranges in a character alternative, by +writing the starting and ending characters with a @samp{-} between them. +Thus, @samp{[a-z]} matches any lower-case @acronym{ASCII} letter. +Ranges may be intermixed freely with individual characters, as in +@samp{[a-z$%.]}, which matches any lower case @acronym{ASCII} letter +or @samp{$}, @samp{%} or period. + +Note that the usual regexp special characters are not special inside a +character alternative. A completely different set of characters is +special inside character alternatives: @samp{]}, @samp{-} and @samp{^}. + +To include a @samp{]} in a character alternative, you must make it the +first character. For example, @samp{[]a]} matches @samp{]} or @samp{a}. +To include a @samp{-}, write @samp{-} as the first or last character of +the character alternative, or put it after a range. Thus, @samp{[]-]} +matches both @samp{]} and @samp{-}. + +To include @samp{^} in a character alternative, put it anywhere but at +the beginning. + +The beginning and end of a range of multibyte characters must be in +the same character set (@pxref{Character Sets}). Thus, +@code{"[\x8e0-\x97c]"} is invalid because character 0x8e0 (@samp{a} +with grave accent) is in the Emacs character set for Latin-1 but the +character 0x97c (@samp{u} with diaeresis) is in the Emacs character +set for Latin-2. (We use Lisp string syntax to write that example, +and a few others in the next few paragraphs, in order to include hex +escape sequences in them.) + +If a range starts with a unibyte character @var{c} and ends with a +multibyte character @var{c2}, the range is divided into two parts: one +is @samp{@var{c}..?\377}, the other is @samp{@var{c1}..@var{c2}}, where +@var{c1} is the first character of the charset to which @var{c2} +belongs. + +You cannot always match all non-@acronym{ASCII} characters with the regular +expression @code{"[\200-\377]"}. This works when searching a unibyte +buffer or string (@pxref{Text Representations}), but not in a multibyte +buffer or string, because many non-@acronym{ASCII} characters have codes +above octal 0377. However, the regular expression @code{"[^\000-\177]"} +does match all non-@acronym{ASCII} characters (see below regarding @samp{^}), +in both multibyte and unibyte representations, because only the +@acronym{ASCII} characters are excluded. + +A character alternative can also specify named +character classes (@pxref{Char Classes}). This is a POSIX feature whose +syntax is @samp{[:@var{class}:]}. Using a character class is equivalent +to mentioning each of the characters in that class; but the latter is +not feasible in practice, since some classes include thousands of +different characters. + +@item @samp{[^ @dots{} ]} @cindex @samp{^} in regexp -@samp{[^} begins a @dfn{complement character set}, which matches any -character except the ones specified. Thus, @samp{[^a-z0-9A-Z]} -matches all characters @emph{except} letters and digits.@refill +@samp{[^} begins a @dfn{complemented character alternative}. This +matches any character except the ones specified. Thus, +@samp{[^a-z0-9A-Z]} matches all characters @emph{except} letters and +digits. -@samp{^} is not special in a character set unless it is the first +@samp{^} is not special in a character alternative unless it is the first character. The character following the @samp{^} is treated as if it -were first (thus, @samp{-} and @samp{]} are not special there). +were first (in other words, @samp{-} and @samp{]} are not special there). -Note that a complement character set can match a newline, unless -newline is mentioned as one of the characters not to match. +A complemented character alternative can match a newline, unless newline is +mentioned as one of the characters not to match. This is in contrast to +the handling of regexps in programs such as @code{grep}. -@item ^ -@cindex @samp{^} in regexp +@item @samp{^} @cindex beginning of line in regexp -is a special character that matches the empty string, but only at -the beginning of a line in the text being matched. Otherwise it fails -to match anything. Thus, @samp{^foo} matches a @samp{foo} which occurs -at the beginning of a line. +When matching a buffer, @samp{^} matches the empty string, but only at the +beginning of a line in the text being matched (or the beginning of the +accessible portion of the buffer). Otherwise it fails to match +anything. Thus, @samp{^foo} matches a @samp{foo} that occurs at the +beginning of a line. + +When matching a string instead of a buffer, @samp{^} matches at the +beginning of the string or after a newline character. -When matching a string, @samp{^} matches at the beginning of the string -or after a newline character @samp{\n}. +For historical compatibility reasons, @samp{^} can be used only at the +beginning of the regular expression, or after @samp{\(} or @samp{\|}. -@item $ +@item @samp{$} @cindex @samp{$} in regexp -is similar to @samp{^} but matches only at the end of a line. Thus, -@samp{x+$} matches a string of one @samp{x} or more at the end of a line. +@cindex end of line in regexp +is similar to @samp{^} but matches only at the end of a line (or the +end of the accessible portion of the buffer). Thus, @samp{x+$} +matches a string of one @samp{x} or more at the end of a line. -When matching a string, @samp{$} matches at the end of the string -or before a newline character @samp{\n}. +When matching a string instead of a buffer, @samp{$} matches at the end +of the string or before a newline character. -@item \ +For historical compatibility reasons, @samp{$} can be used only at the +end of the regular expression, or before @samp{\)} or @samp{\|}. + +@item @samp{\} @cindex @samp{\} in regexp has two functions: it quotes the special characters (including @samp{\}), and it introduces additional special constructs. Because @samp{\} quotes special characters, @samp{\$} is a regular -expression which matches only @samp{$}, and @samp{\[} is a regular -expression which matches only @samp{[}, and so on. +expression that matches only @samp{$}, and @samp{\[} is a regular +expression that matches only @samp{[}, and so on. Note that @samp{\} also has special meaning in the read syntax of Lisp strings (@pxref{String Type}), and must be quoted with @samp{\}. For @@ -318,21 +471,107 @@ example, the regular expression that matches the @samp{\} character is @samp{\} is @code{"\\\\"}.@refill @end table -@strong{Please note:} for historical compatibility, special characters +@strong{Please note:} For historical compatibility, special characters are treated as ordinary ones if they are in contexts where their special meanings make no sense. For example, @samp{*foo} treats @samp{*} as ordinary since there is no preceding expression on which the @samp{*} -can act. It is poor practice to depend on this behavior; better to -quote the special character anyway, regardless of where it -appears.@refill +can act. It is poor practice to depend on this behavior; quote the +special character anyway, regardless of where it appears.@refill + +As a @samp{\} is not special inside a character alternative, it can +never remove the special meaning of @samp{-} or @samp{]}. So you +should not quote these characters when they have no special meaning +either. This would not clarify anything, since backslashes can +legitimately precede these characters where they @emph{have} special +meaning, as in @samp{[^\]} (@code{"[^\\]"} for Lisp string syntax), +which matches any single character except a backslash. + +In practice, most @samp{]} that occur in regular expressions close a +character alternative and hence are special. However, occasionally a +regular expression may try to match a complex pattern of literal +@samp{[} and @samp{]}. In such situations, it sometimes may be +necessary to carefully parse the regexp from the start to determine +which square brackets enclose a character alternative. For example, +@samp{[^][]]} consists of the complemented character alternative +@samp{[^][]} (which matches any single character that is not a square +bracket), followed by a literal @samp{]}. + +The exact rules are that at the beginning of a regexp, @samp{[} is +special and @samp{]} not. This lasts until the first unquoted +@samp{[}, after which we are in a character alternative; @samp{[} is +no longer special (except when it starts a character class) but @samp{]} +is special, unless it immediately follows the special @samp{[} or that +@samp{[} followed by a @samp{^}. This lasts until the next special +@samp{]} that does not end a character class. This ends the character +alternative and restores the ordinary syntax of regular expressions; +an unquoted @samp{[} is special again and a @samp{]} not. + +@node Char Classes +@subsubsection Character Classes +@cindex character classes in regexp + + Here is a table of the classes you can use in a character alternative, +and what they mean: + +@table @samp +@item [:ascii:] +This matches any @acronym{ASCII} character (codes 0--127). +@item [:alnum:] +This matches any letter or digit. (At present, for multibyte +characters, it matches anything that has word syntax.) +@item [:alpha:] +This matches any letter. (At present, for multibyte characters, it +matches anything that has word syntax.) +@item [:blank:] +This matches space and tab only. +@item [:cntrl:] +This matches any @acronym{ASCII} control character. +@item [:digit:] +This matches @samp{0} through @samp{9}. Thus, @samp{[-+[:digit:]]} +matches any digit, as well as @samp{+} and @samp{-}. +@item [:graph:] +This matches graphic characters---everything except @acronym{ASCII} control +characters, space, and the delete character. +@item [:lower:] +This matches any lower-case letter, as determined by +the current case table (@pxref{Case Tables}). +@item [:multibyte:] +This matches any multibyte character (@pxref{Text Representations}). +@item [:nonascii:] +This matches any non-@acronym{ASCII} character. +@item [:print:] +This matches printing characters---everything except @acronym{ASCII} control +characters and the delete character. +@item [:punct:] +This matches any punctuation character. (At present, for multibyte +characters, it matches anything that has non-word syntax.) +@item [:space:] +This matches any character that has whitespace syntax +(@pxref{Syntax Class Table}). +@item [:unibyte:] +This matches any unibyte character (@pxref{Text Representations}). +@item [:upper:] +This matches any upper-case letter, as determined by +the current case table (@pxref{Case Tables}). +@item [:word:] +This matches any character that has word syntax (@pxref{Syntax Class +Table}). +@item [:xdigit:] +This matches the hexadecimal digits: @samp{0} through @samp{9}, @samp{a} +through @samp{f} and @samp{A} through @samp{F}. +@end table + +@node Regexp Backslash +@subsubsection Backslash Constructs in Regular Expressions -For the most part, @samp{\} followed by any character matches only -that character. However, there are several exceptions: characters -which, when preceded by @samp{\}, are special constructs. Such -characters are always ordinary when encountered on their own. Here -is a table of @samp{\} constructs: + For the most part, @samp{\} followed by any character matches only +that character. However, there are several exceptions: certain +two-character sequences starting with @samp{\} that have special +meanings. (The character after the @samp{\} in such a sequence is +always ordinary when used on its own.) Here is a table of the special +@samp{\} constructs. -@table @kbd +@table @samp @item \| @cindex @samp{|} in regexp @cindex regexp alternative @@ -348,7 +587,28 @@ but no other string.@refill surrounding @samp{\( @dots{} \)} grouping can limit the grouping power of @samp{\|}.@refill -Full backtracking capability exists to handle multiple uses of @samp{\|}. +If you need full backtracking capability to handle multiple uses of +@samp{\|}, use the POSIX regular expression functions (@pxref{POSIX +Regexps}). + +@item \@{@var{m}\@} +is a postfix operator that repeats the previous pattern exactly @var{m} +times. Thus, @samp{x\@{5\@}} matches the string @samp{xxxxx} +and nothing else. @samp{c[ad]\@{3\@}r} matches string such as +@samp{caaar}, @samp{cdddr}, @samp{cadar}, and so on. + +@item \@{@var{m},@var{n}\@} +is a more general postfix operator that specifies repetition with a +minimum of @var{m} repeats and a maximum of @var{n} repeats. If @var{m} +is omitted, the minimum is 0; if @var{n} is omitted, there is no +maximum. + +For example, @samp{c[ad]\@{1,2\@}r} matches the strings @samp{car}, +@samp{cdr}, @samp{caar}, @samp{cadr}, @samp{cdar}, and @samp{cddr}, and +nothing else.@* +@samp{\@{0,1\@}} or @samp{\@{,1\@}} is equivalent to @samp{?}. @* +@samp{\@{0,\@}} or @samp{\@{,\@}} is equivalent to @samp{*}. @* +@samp{\@{1,\@}} is equivalent to @samp{+}. @item \( @dots{} \) @cindex @samp{(} in regexp @@ -358,45 +618,73 @@ is a grouping construct that serves three purposes: @enumerate @item -To enclose a set of @samp{\|} alternatives for other operations. -Thus, @samp{\(foo\|bar\)x} matches either @samp{foox} or @samp{barx}. +To enclose a set of @samp{\|} alternatives for other operations. Thus, +the regular expression @samp{\(foo\|bar\)x} matches either @samp{foox} +or @samp{barx}. @item -To enclose an expression for a suffix operator such as @samp{*} to act -on. Thus, @samp{ba\(na\)*} matches @samp{bananana}, etc., with any -(zero or more) number of @samp{na} strings.@refill +To enclose a complicated expression for the postfix operators @samp{*}, +@samp{+} and @samp{?} to operate on. Thus, @samp{ba\(na\)*} matches +@samp{ba}, @samp{bana}, @samp{banana}, @samp{bananana}, etc., with any +number (zero or more) of @samp{na} strings. @item -To record a matched substring for future reference. +To record a matched substring for future reference with +@samp{\@var{digit}} (see below). @end enumerate This last application is not a consequence of the idea of a -parenthetical grouping; it is a separate feature which happens to be -assigned as a second meaning to the same @samp{\( @dots{} \)} construct -because there is no conflict in practice between the two meanings. -Here is an explanation of this feature: +parenthetical grouping; it is a separate feature that was assigned as a +second meaning to the same @samp{\( @dots{} \)} construct because, in +practice, there was usually no conflict between the two meanings. But +occasionally there is a conflict, and that led to the introduction of +shy groups. + +@item \(?: @dots{} \) +is the @dfn{shy group} construct. A shy group serves the first two +purposes of an ordinary group (controlling the nesting of other +operators), but it does not get a number, so you cannot refer back to +its value with @samp{\@var{digit}}. + +Shy groups are particularly useful for mechanically-constructed regular +expressions because they can be added automatically without altering the +numbering of any ordinary, non-shy groups. @item \@var{digit} -matches the same text which matched the @var{digit}th occurrence of a -@samp{\( @dots{} \)} construct. +matches the same text that matched the @var{digit}th occurrence of a +grouping (@samp{\( @dots{} \)}) construct. -In other words, after the end of a @samp{\( @dots{} \)} construct. the -matcher remembers the beginning and end of the text matched by that -construct. Then, later on in the regular expression, you can use -@samp{\} followed by @var{digit} to match that same text, whatever it -may have been. +In other words, after the end of a group, the matcher remembers the +beginning and end of the text matched by that group. Later on in the +regular expression you can use @samp{\} followed by @var{digit} to +match that same text, whatever it may have been. -The strings matching the first nine @samp{\( @dots{} \)} constructs -appearing in a regular expression are assigned numbers 1 through 9 in -the order that the open parentheses appear in the regular expression. -So you can use @samp{\1} through @samp{\9} to refer to the text matched -by the corresponding @samp{\( @dots{} \)} constructs. +The strings matching the first nine grouping constructs appearing in +the entire regular expression passed to a search or matching function +are assigned numbers 1 through 9 in the order that the open +parentheses appear in the regular expression. So you can use +@samp{\1} through @samp{\9} to refer to the text matched by the +corresponding grouping constructs. For example, @samp{\(.*\)\1} matches any newline-free string that is composed of two identical halves. The @samp{\(.*\)} matches the first half, which may be anything, but the @samp{\1} that follows must match the same exact text. +If a @samp{\( @dots{} \)} construct matches more than once (which can +happen, for instance, if it is followed by @samp{*}), only the last +match is recorded. + +If a particular grouping construct in the regular expression was never +matched---for instance, if it appears inside of an alternative that +wasn't used, or inside of a repetition that repeated zero times---then +the corresponding @samp{\@var{digit}} construct never matches +anything. To use an artificial example,, @samp{\(foo\(b*\)\|lose\)\2} +cannot match @samp{lose}: the second alternative inside the larger +group matches it, but then @samp{\2} is undefined and can't match +anything. But it can match @samp{foobb}, because the first +alternative matches @samp{foob} and @samp{\2} matches @samp{b}. + @item \w @cindex @samp{\w} in regexp matches any word-constituent character. The editor syntax table @@ -404,26 +692,38 @@ determines which characters these are. @xref{Syntax Tables}. @item \W @cindex @samp{\W} in regexp -matches any character that is not a word-constituent. +matches any character that is not a word constituent. @item \s@var{code} @cindex @samp{\s} in regexp matches any character whose syntax is @var{code}. Here @var{code} is a -character which represents a syntax code: thus, @samp{w} for word +character that represents a syntax code: thus, @samp{w} for word constituent, @samp{-} for whitespace, @samp{(} for open parenthesis, -etc. @xref{Syntax Tables}, for a list of syntax codes and the -characters that stand for them. +etc. To represent whitespace syntax, use either @samp{-} or a space +character. @xref{Syntax Class Table}, for a list of syntax codes and +the characters that stand for them. @item \S@var{code} @cindex @samp{\S} in regexp matches any character whose syntax is not @var{code}. + +@item \c@var{c} +matches any character whose category is @var{c}. Here @var{c} is a +character that represents a category: thus, @samp{c} for Chinese +characters or @samp{g} for Greek characters in the standard category +table. + +@item \C@var{c} +matches any character whose category is not @var{c}. @end table - These regular expression constructs match the empty string---that is, + The following regular expression constructs match the empty string---that is, they don't use up any characters---but whether they match depends on the -context. +context. For all, the beginning and end of the accessible portion of +the buffer are treated as if they were the actual beginning and end of +the buffer. -@table @kbd +@table @samp @item \` @cindex @samp{\`} in regexp matches the empty string, but only at the beginning @@ -446,59 +746,56 @@ end of a word. Thus, @samp{\bfoo\b} matches any occurrence of @samp{foo} as a separate word. @samp{\bballs?\b} matches @samp{ball} or @samp{balls} as a separate word.@refill +@samp{\b} matches at the beginning or end of the buffer (or string) +regardless of what text appears next to it. + @item \B @cindex @samp{\B} in regexp matches the empty string, but @emph{not} at the beginning or -end of a word. +end of a word, nor at the beginning or end of the buffer (or string). @item \< @cindex @samp{\<} in regexp matches the empty string, but only at the beginning of a word. +@samp{\<} matches at the beginning of the buffer (or string) only if a +word-constituent character follows. @item \> @cindex @samp{\>} in regexp -matches the empty string, but only at the end of a word. +matches the empty string, but only at the end of a word. @samp{\>} +matches at the end of the buffer (or string) only if the contents end +with a word-constituent character. + +@item \_< +@cindex @samp{\_<} in regexp +matches the empty string, but only at the beginning of a symbol. A +symbol is a sequence of one or more word or symbol constituent +characters. @samp{\_<} matches at the beginning of the buffer (or +string) only if a symbol-constituent character follows. + +@item \_> +@cindex @samp{\_>} in regexp +matches the empty string, but only at the end of a symbol. @samp{\_>} +matches at the end of the buffer (or string) only if the contents end +with a symbol-constituent character. @end table @kindex invalid-regexp Not every string is a valid regular expression. For example, a string -with unbalanced square brackets is invalid (with a few exceptions, such -as @samp{[]]}, and so is a string that ends with a single @samp{\}. If +that ends inside a character alternative without terminating @samp{]} +is invalid, and so is a string that ends with a single @samp{\}. If an invalid regular expression is passed to any of the search functions, an @code{invalid-regexp} error is signaled. -@defun regexp-quote string -This function returns a regular expression string that matches exactly -@var{string} and nothing else. This allows you to request an exact -string match when calling a function that wants a regular expression. - -@example -@group -(regexp-quote "^The cat$") - @result{} "\\^The cat\\$" -@end group -@end example - -One use of @code{regexp-quote} is to combine an exact string match with -context described as a regular expression. For example, this searches -for the string which is the value of @code{string}, surrounded by -whitespace: - -@example -@group -(re-search-forward - (concat "\\s " (regexp-quote string) "\\s ")) -@end group -@end example -@end defun - @node Regexp Example @comment node-name, next, previous, up @subsection Complex Regexp Example - Here is a complicated regexp, used by Emacs to recognize the end of a -sentence together with any whitespace that follows. It is the value of -the variable @code{sentence-end}. + Here is a complicated regexp which was formerly used by Emacs to +recognize the end of a sentence together with any whitespace that +follows. (Nowadays Emacs uses a similar but more complex default +regexp constructed by the function @code{sentence-end}. +@xref{Standard Regexps}.) First, we show the regexp as a string in Lisp syntax to distinguish spaces from tab characters. The string constant begins and ends with a @@ -507,17 +804,16 @@ string, @samp{\\} for a backslash as part of the string, @samp{\t} for a tab and @samp{\n} for a newline. @example -"[.?!][]\"')@}]*\\($\\| $\\|\t\\| \\)[ \t\n]*" +"[.?!][]\"')@}]*\\($\\| $\\|\t\\|@ @ \\)[ \t\n]*" @end example - In contrast, if you evaluate the variable @code{sentence-end}, you -will see the following: +@noindent +In contrast, if you evaluate this string, you will see the following: @example @group -sentence-end -@result{} -"[.?!][]\"')@}]*\\($\\| $\\| \\| \\)[ +"[.?!][]\"')@}]*\\($\\| $\\|\t\\|@ @ \\)[ \t\n]*" + @result{} "[.?!][]\"')@}]*\\($\\| $\\| \\|@ @ \\)[ ]*" @end group @end example @@ -530,42 +826,115 @@ deciphered as follows: @table @code @item [.?!] -The first part of the pattern consists of three characters, a period, a -question mark and an exclamation mark, within square brackets. The -match must begin with one of these three characters. +The first part of the pattern is a character alternative that matches +any one of three characters: period, question mark, and exclamation +mark. The match must begin with one of these three characters. (This +is one point where the new default regexp used by Emacs differs from +the old. The new value also allows some non-@acronym{ASCII} +characters that end a sentence without any following whitespace.) @item []\"')@}]* The second part of the pattern matches any closing braces and quotation marks, zero or more of them, that may follow the period, question mark or exclamation mark. The @code{\"} is Lisp syntax for a double-quote in a string. The @samp{*} at the end indicates that the immediately -preceding regular expression (a character set, in this case) may be +preceding regular expression (a character alternative, in this case) may be repeated zero or more times. -@item \\($\\|@ \\|\t\\|@ @ \\) +@item \\($\\|@ $\\|\t\\|@ @ \\) The third part of the pattern matches the whitespace that follows the -end of a sentence: the end of a line, or a tab, or two spaces. The -double backslashes mark the parentheses and vertical bars as regular -expression syntax; the parentheses mark the group and the vertical bars -separate alternatives. The dollar sign is used to match the end of a -line. +end of a sentence: the end of a line (optionally with a space), or a +tab, or two spaces. The double backslashes mark the parentheses and +vertical bars as regular expression syntax; the parentheses delimit a +group and the vertical bars separate alternatives. The dollar sign is +used to match the end of a line. @item [ \t\n]* Finally, the last part of the pattern matches any additional whitespace beyond the minimum needed to end a sentence. @end table +@node Regexp Functions +@subsection Regular Expression Functions + + These functions operate on regular expressions. + +@defun regexp-quote string +This function returns a regular expression whose only exact match is +@var{string}. Using this regular expression in @code{looking-at} will +succeed only if the next characters in the buffer are @var{string}; +using it in a search function will succeed if the text being searched +contains @var{string}. + +This allows you to request an exact string match or search when calling +a function that wants a regular expression. + +@example +@group +(regexp-quote "^The cat$") + @result{} "\\^The cat\\$" +@end group +@end example + +One use of @code{regexp-quote} is to combine an exact string match with +context described as a regular expression. For example, this searches +for the string that is the value of @var{string}, surrounded by +whitespace: + +@example +@group +(re-search-forward + (concat "\\s-" (regexp-quote string) "\\s-")) +@end group +@end example +@end defun + +@defun regexp-opt strings &optional paren +This function returns an efficient regular expression that will match +any of the strings in the list @var{strings}. This is useful when you +need to make matching or searching as fast as possible---for example, +for Font Lock mode. + +If the optional argument @var{paren} is non-@code{nil}, then the +returned regular expression is always enclosed by at least one +parentheses-grouping construct. If @var{paren} is @code{words}, then +that construct is additionally surrounded by @samp{\<} and @samp{\>}. + +This simplified definition of @code{regexp-opt} produces a +regular expression which is equivalent to the actual value +(but not as efficient): + +@example +(defun regexp-opt (strings paren) + (let ((open-paren (if paren "\\(" "")) + (close-paren (if paren "\\)" ""))) + (concat open-paren + (mapconcat 'regexp-quote strings "\\|") + close-paren))) +@end example +@end defun + +@defun regexp-opt-depth regexp +This function returns the total number of grouping constructs +(parenthesized expressions) in @var{regexp}. (This does not include +shy groups.) +@end defun + @node Regexp Search @section Regular Expression Searching @cindex regular expression searching @cindex regexp searching @cindex searching for regexp - In GNU Emacs, you can search for the next match for a regexp either -incrementally or not. For incremental search commands, see @ref{Regexp -Search, , Regular Expression Search, emacs, The GNU Emacs Manual}. Here -we describe only the search functions useful in programs. The principal -one is @code{re-search-forward}. + In GNU Emacs, you can search for the next match for a regular +expression either incrementally or not. For incremental search +commands, see @ref{Regexp Search, , Regular Expression Search, emacs, +The GNU Emacs Manual}. Here we describe only the search functions +useful in programs. The principal one is @code{re-search-forward}. + + These search functions convert the regular expression to multibyte if +the buffer is multibyte; they convert the regular expression to unibyte +if the buffer is unibyte. @xref{Text Representations}. @deffn Command re-search-forward regexp &optional limit noerror repeat This function searches forward in the current buffer for a string of @@ -574,23 +943,26 @@ function skips over any amount of text that is not matched by @var{regexp}, and leaves point at the end of the first match found. It returns the new value of point. -If @var{limit} is non-@code{nil} (it must be a position in the current -buffer), then it is the upper bound to the search. No match extending -after that position is accepted. +If @var{limit} is non-@code{nil}, it must be a position in the current +buffer. It specifies the upper bound to the search. No match +extending after that position is accepted. -What happens when the search fails depends on the value of -@var{noerror}. If @var{noerror} is @code{nil}, a @code{search-failed} -error is signaled. If @var{noerror} is @code{t}, -@code{re-search-forward} does nothing and returns @code{nil}. If -@var{noerror} is neither @code{nil} nor @code{t}, then -@code{re-search-forward} moves point to @var{limit} (or the end of the -buffer) and returns @code{nil}. +If @var{repeat} is supplied, it must be a positive number; the search +is repeated that many times; each repetition starts at the end of the +previous match. If all these successive searches succeed, the search +succeeds, moving point and returning its new value. Otherwise the +search fails. What @code{re-search-forward} does when the search +fails depends on the value of @var{noerror}: -If @var{repeat} is supplied (it must be a positive number), then the -search is repeated that many times (each time starting at the end of the -previous time's match). If these successive searches succeed, the -function succeeds, moving point and returning its new value. Otherwise -the search fails. +@table @asis +@item @code{nil} +Signal a @code{search-failed} error. +@item @code{t} +Do nothing and return @code{nil}. +@item anything else +Move point to @var{limit} (or the end of the accessible portion of the +buffer) and return @code{nil}. +@end table In the following example, point is initially before the @samp{T}. Evaluating the search call moves point to the end of that line (between @@ -621,18 +993,19 @@ This function searches backward in the current buffer for a string of text that is matched by the regular expression @var{regexp}, leaving point at the beginning of the first text found. -This function is analogous to @code{re-search-forward}, but they are -not simple mirror images. @code{re-search-forward} finds the match -whose beginning is as close as possible. If @code{re-search-backward} -were a perfect mirror image, it would find the match whose end is as -close as possible. However, in fact it finds the match whose beginning -is as close as possible. The reason is that matching a regular -expression at a given spot always works from beginning to end, and is -done at a specified beginning position. +This function is analogous to @code{re-search-forward}, but they are not +simple mirror images. @code{re-search-forward} finds the match whose +beginning is as close as possible to the starting point. If +@code{re-search-backward} were a perfect mirror image, it would find the +match whose end is as close as possible. However, in fact it finds the +match whose beginning is as close as possible (and yet ends before the +starting point). The reason for this is that matching a regular +expression at a given spot always works from beginning to end, and +starts at a specified beginning position. A true mirror-image of @code{re-search-forward} would require a special -feature for matching regexps from end to beginning. It's not worth the -trouble of implementing that. +feature for matching regular expressions from end to beginning. It's +not worth the trouble of implementing that. @end deffn @defun string-match regexp string &optional start @@ -704,180 +1077,97 @@ comes back" twice. @end example @end defun -@ignore -@deffn Command delete-matching-lines regexp -This function is identical to @code{delete-non-matching-lines}, save -that it deletes what @code{delete-non-matching-lines} keeps. +@defun looking-back regexp &optional limit +This function returns @code{t} if @var{regexp} matches text before +point, ending at point, and @code{nil} otherwise. -In the example below, point is located on the first line of text. +Because regular expression matching works only going forward, this is +implemented by searching backwards from point for a match that ends at +point. That can be quite slow if it has to search a long distance. +You can bound the time required by specifying @var{limit}, which says +not to search before @var{limit}. In this case, the match that is +found must begin at or after @var{limit}. @example @group ---------- Buffer: foo ---------- -We hold these truths -to be self-evident, -that all men are created -equal, and that they are +I read "@point{}The cat in the hat +comes back" twice. ---------- Buffer: foo ---------- -@end group -@group -(delete-matching-lines "the") +(looking-back "read \"" 3) + @result{} t +(looking-back "read \"" 4) @result{} nil - ----------- Buffer: foo ---------- -to be self-evident, -that all men are created ----------- Buffer: foo ---------- @end group @end example -@end deffn - -@deffn Command flush-lines regexp -This function is the same as @code{delete-matching-lines}. -@end deffn - -@defun delete-non-matching-lines regexp -This function deletes all lines following point which don't -contain a match for the regular expression @var{regexp}. @end defun -@deffn Command keep-lines regexp -This function is the same as @code{delete-non-matching-lines}. -@end deffn - -@deffn Command how-many regexp -This function counts the number of matches for @var{regexp} there are in -the current buffer following point. It prints this number in -the echo area, returning the string printed. -@end deffn - -@deffn Command count-matches regexp -This function is a synonym of @code{how-many}. -@end deffn - -@deffn Command list-matching-lines regexp nlines -This function is a synonym of @code{occur}. -Show all lines following point containing a match for @var{regexp}. -Display each line with @var{nlines} lines before and after, -or @code{-}@var{nlines} before if @var{nlines} is negative. -@var{nlines} defaults to @code{list-matching-lines-default-context-lines}. -Interactively it is the prefix arg. - -The lines are shown in a buffer named @samp{*Occur*}. -It serves as a menu to find any of the occurrences in this buffer. -@kbd{C-h m} (@code{describe-mode} in that buffer gives help. -@end deffn - -@defopt list-matching-lines-default-context-lines -Default value is 0. -Default number of context lines to include around a @code{list-matching-lines} -match. A negative number means to include that many lines before the match. -A positive number means to include that many lines both before and after. -@end defopt -@end ignore - -@node Search and Replace -@section Search and Replace -@cindex replacement - -@defun perform-replace from-string replacements query-flag regexp-flag delimited-flag &optional repeat-count map -This function is the guts of @code{query-replace} and related commands. -It searches for occurrences of @var{from-string} and replaces some or -all of them. If @var{query-flag} is @code{nil}, it replaces all -occurrences; otherwise, it asks the user what to do about each one. - -If @var{regexp-flag} is non-@code{nil}, then @var{from-string} is -considered a regular expression; otherwise, it must match literally. If -@var{delimited-flag} is non-@code{nil}, then only replacements -surrounded by word boundaries are considered. - -The argument @var{replacements} specifies what to replace occurrences -with. If it is a string, that string is used. It can also be a list of -strings, to be used in cyclic order. - -If @var{repeat-count} is non-@code{nil}, it should be an integer, the -number of occurrences to consider. In this case, @code{perform-replace} -returns after considering that many occurrences. - -Normally, the keymap @code{query-replace-map} defines the possible user -responses. The argument @var{map}, if non-@code{nil}, is a keymap to -use instead of @code{query-replace-map}. -@end defun - -@defvar query-replace-map -This variable holds a special keymap that defines the valid user -responses for @code{query-replace} and related functions, as well as -@code{y-or-n-p} and @code{map-y-or-n-p}. It is unusual in two ways: - -@itemize @bullet -@item -The ``key bindings'' are not commands, just symbols that are meaningful -to the functions that use this map. - -@item -Prefix keys are not supported; each key binding must be for a single event -key sequence. This is because the functions don't use read key sequence to -get the input; instead, they read a single event and look it up ``by hand.'' -@end itemize +@defvar search-spaces-regexp +If this variable is non-@code{nil}, it should be a regular expression +that says how to search for whitespace. In that case, any group of +spaces in a regular expression being searched for stands for use of +this regular expression. However, spaces inside of constructs such as +@samp{[@dots{}]} and @samp{*}, @samp{+}, @samp{?} are not affected by +@code{search-spaces-regexp}. + +Since this variable affects all regular expression search and match +constructs, you should bind it temporarily for as small as possible +a part of the code. @end defvar -Here are the meaningful ``bindings'' for @code{query-replace-map}. -Several of them are meaningful only for @code{query-replace} and -friends. - -@table @code -@item act -Do take the action being considered---in other words, ``yes.'' - -@item skip -Do not take action for this question---in other words, ``no.'' - -@item exit -Answer this question ``no,'' and don't ask any more. - -@item act-and-exit -Answer this question ``yes,'' and don't ask any more. - -@item act-and-show -Answer this question ``yes,'' but show the results---don't advance yet -to the next question. - -@item automatic -Answer this question and all subsequent questions in the series with -``yes,'' without further user interaction. - -@item backup -Move back to the previous place that a question was asked about. - -@item edit -Enter a recursive edit to deal with this question---instead of any -other action that would normally be taken. - -@item delete-and-edit -Delete the text being considered, then enter a recursive edit to replace -it. +@node POSIX Regexps +@section POSIX Regular Expression Searching + + The usual regular expression functions do backtracking when necessary +to handle the @samp{\|} and repetition constructs, but they continue +this only until they find @emph{some} match. Then they succeed and +report the first match found. + + This section describes alternative search functions which perform the +full backtracking specified by the POSIX standard for regular expression +matching. They continue backtracking until they have tried all +possibilities and found all matches, so they can report the longest +match, as required by POSIX. This is much slower, so use these +functions only when you really need the longest match. + + The POSIX search and match functions do not properly support the +non-greedy repetition operators. This is because POSIX backtracking +conflicts with the semantics of non-greedy repetition. + +@defun posix-search-forward regexp &optional limit noerror repeat +This is like @code{re-search-forward} except that it performs the full +backtracking specified by the POSIX standard for regular expression +matching. +@end defun -@item recenter -Redisplay and center the window, then ask the same question again. +@defun posix-search-backward regexp &optional limit noerror repeat +This is like @code{re-search-backward} except that it performs the full +backtracking specified by the POSIX standard for regular expression +matching. +@end defun -@item quit -Perform a quit right away. Only @code{y-or-n-p} and related functions -use this answer. +@defun posix-looking-at regexp +This is like @code{looking-at} except that it performs the full +backtracking specified by the POSIX standard for regular expression +matching. +@end defun -@item help -Display some help, then ask again. -@end table +@defun posix-string-match regexp string &optional start +This is like @code{string-match} except that it performs the full +backtracking specified by the POSIX standard for regular expression +matching. +@end defun @node Match Data @section The Match Data @cindex match data - Emacs keeps track of the positions of the start and end of segments of -text found during a regular expression search. This means, for example, -that you can search for a complex pattern, such as a date in an Rmail -message, and then extract parts of the match under control of the -pattern. + Emacs keeps track of the start and end positions of the segments of +text found during a search; this is called the @dfn{match data}. +Thanks to the match data, you can search for a complex pattern, such +as a date in a mail message, and then extract parts of the match under +control of the pattern. Because the match data normally describe the most recent search only, you must be careful not to do another search inadvertently between the @@ -886,45 +1176,151 @@ can't avoid another intervening search, you must save and restore the match data around it, to prevent it from being overwritten. @menu +* Replacing Match:: Replacing a substring that was matched. * Simple Match Data:: Accessing single items of match data, such as where a particular subexpression started. -* Replacing Match:: Replacing a substring that was matched. * Entire Match Data:: Accessing the entire match data at once, as a list. * Saving Match Data:: Saving and restoring the match data. @end menu +@node Replacing Match +@subsection Replacing the Text that Matched + + This function replaces all or part of the text matched by the last +search. It works by means of the match data. + +@cindex case in replacements +@defun replace-match replacement &optional fixedcase literal string subexp +This function replaces the text in the buffer (or in @var{string}) that +was matched by the last search. It replaces that text with +@var{replacement}. + +If you did the last search in a buffer, you should specify @code{nil} +for @var{string} and make sure that the current buffer when you call +@code{replace-match} is the one in which you did the searching or +matching. Then @code{replace-match} does the replacement by editing +the buffer; it leaves point at the end of the replacement text, and +returns @code{t}. + +If you did the search in a string, pass the same string as @var{string}. +Then @code{replace-match} does the replacement by constructing and +returning a new string. + +If @var{fixedcase} is non-@code{nil}, then @code{replace-match} uses +the replacement text without case conversion; otherwise, it converts +the replacement text depending upon the capitalization of the text to +be replaced. If the original text is all upper case, this converts +the replacement text to upper case. If all words of the original text +are capitalized, this capitalizes all the words of the replacement +text. If all the words are one-letter and they are all upper case, +they are treated as capitalized words rather than all-upper-case +words. + +If @var{literal} is non-@code{nil}, then @var{replacement} is inserted +exactly as it is, the only alterations being case changes as needed. +If it is @code{nil} (the default), then the character @samp{\} is treated +specially. If a @samp{\} appears in @var{replacement}, then it must be +part of one of the following sequences: + +@table @asis +@item @samp{\&} +@cindex @samp{&} in replacement +@samp{\&} stands for the entire text being replaced. + +@item @samp{\@var{n}} +@cindex @samp{\@var{n}} in replacement +@samp{\@var{n}}, where @var{n} is a digit, stands for the text that +matched the @var{n}th subexpression in the original regexp. +Subexpressions are those expressions grouped inside @samp{\(@dots{}\)}. +If the @var{n}th subexpression never matched, an empty string is substituted. + +@item @samp{\\} +@cindex @samp{\} in replacement +@samp{\\} stands for a single @samp{\} in the replacement text. +@end table + +These substitutions occur after case conversion, if any, +so the strings they substitute are never case-converted. + +If @var{subexp} is non-@code{nil}, that says to replace just +subexpression number @var{subexp} of the regexp that was matched, not +the entire match. For example, after matching @samp{foo \(ba*r\)}, +calling @code{replace-match} with 1 as @var{subexp} means to replace +just the text that matched @samp{\(ba*r\)}. +@end defun + @node Simple Match Data @subsection Simple Match Data Access - This section explains how to use the match data to find the starting -point or ending point of the text that was matched by a particular -search, or by a particular parenthetical subexpression of a regular -expression. + This section explains how to use the match data to find out what was +matched by the last search or match operation, if it succeeded. + + You can ask about the entire matching text, or about a particular +parenthetical subexpression of a regular expression. The @var{count} +argument in the functions below specifies which. If @var{count} is +zero, you are asking about the entire match. If @var{count} is +positive, it specifies which subexpression you want. + + Recall that the subexpressions of a regular expression are those +expressions grouped with escaped parentheses, @samp{\(@dots{}\)}. The +@var{count}th subexpression is found by counting occurrences of +@samp{\(} from the beginning of the whole regular expression. The first +subexpression is numbered 1, the second 2, and so on. Only regular +expressions can have subexpressions---after a simple string search, the +only information available is about the entire match. + + Every successful search sets the match data. Therefore, you should +query the match data immediately after searching, before calling any +other function that might perform another search. Alternatively, you +may save and restore the match data (@pxref{Saving Match Data}) around +the call to functions that could perform another search. + + A search which fails may or may not alter the match data. In the +past, a failing search did not do this, but we may change it in the +future. So don't try to rely on the value of the match data after +a failing search. + +@defun match-string count &optional in-string +This function returns, as a string, the text matched in the last search +or match operation. It returns the entire text if @var{count} is zero, +or just the portion corresponding to the @var{count}th parenthetical +subexpression, if @var{count} is positive. + +If the last such operation was done against a string with +@code{string-match}, then you should pass the same string as the +argument @var{in-string}. After a buffer search or match, +you should omit @var{in-string} or pass @code{nil} for it; but you +should make sure that the current buffer when you call +@code{match-string} is the one in which you did the searching or +matching. + +The value is @code{nil} if @var{count} is out of range, or for a +subexpression inside a @samp{\|} alternative that wasn't used or a +repetition that repeated zero times. +@end defun + +@defun match-string-no-properties count &optional in-string +This function is like @code{match-string} except that the result +has no text properties. +@end defun @defun match-beginning count This function returns the position of the start of text matched by the last regular expression searched for, or a subexpression of it. -The argument @var{count}, a number, specifies a subexpression whose -start position is the value. If @var{count} is zero, then the value is -the position of the text matched by the whole regexp. If @var{count} is -greater than zero, then the value is the position of the beginning of -the text matched by the @var{count}th subexpression. +If @var{count} is zero, then the value is the position of the start of +the entire match. Otherwise, @var{count} specifies a subexpression in +the regular expression, and the value of the function is the starting +position of the match for that subexpression. -Subexpressions of a regular expression are those expressions grouped -inside of parentheses, @samp{\(@dots{}\)}. The @var{count}th -subexpression is found by counting occurrences of @samp{\(} from the -beginning of the whole regular expression. The first subexpression is -numbered 1, the second 2, and so on. - -The value is @code{nil} for a parenthetical grouping inside of a -@samp{\|} alternative that wasn't used in the match. +The value is @code{nil} for a subexpression inside a @samp{\|} +alternative that wasn't used or a repetition that repeated zero times. @end defun @defun match-end count -This function returns the position of the end of the text that matched -the last regular expression searched for, or a subexpression of it. -This function is otherwise similar to @code{match-beginning}. +This function is like @code{match-beginning} except that it returns the +position of the end of the match, rather than the position of the +beginning. @end defun Here is an example of using the match data, with a comment showing the @@ -934,10 +1330,19 @@ positions within the text: @group (string-match "\\(qu\\)\\(ick\\)" "The quick fox jumped quickly.") - ;0123456789 + ;0123456789 @result{} 4 @end group +@group +(match-string 0 "The quick fox jumped quickly.") + @result{} "quick" +(match-string 1 "The quick fox jumped quickly.") + @result{} "qu" +(match-string 2 "The quick fox jumped quickly.") + @result{} "ick" +@end group + @group (match-beginning 1) ; @r{The beginning of the match} @result{} 4 ; @r{with @samp{qu} is at index 4.} @@ -969,7 +1374,7 @@ subexpression is at the 13th character (@samp{c}). (re-search-forward "The \\(cat \\)") (match-beginning 0) (match-beginning 1)) - @result{} (t 9 13) + @result{} (9 9 13) @end group @group @@ -985,89 +1390,55 @@ I read "The cat @point{}in the hat comes back" twice. (In this case, the index returned is a buffer position; the first character of the buffer counts as 1.) -@node Replacing Match -@subsection Replacing the Text That Matched - - This function replaces the text matched by the last search with -@var{replacement}. - -@cindex case in replacements -@defun replace-match replacement &optional fixedcase literal -This function replaces the buffer text matched by the last search, with -@var{replacement}. It applies only to buffers; you can't use -@code{replace-match} to replace a substring found with -@code{string-match}. - -If @var{fixedcase} is non-@code{nil}, then the case of the replacement -text is not changed; otherwise, the replacement text is converted to a -different case depending upon the capitalization of the text to be -replaced. If the original text is all upper case, the replacement text -is converted to upper case, except when all of the words in the original -text are only one character long. In that event, the replacement text -is capitalized. If @emph{any} of the words in the original text is -capitalized, then all of the words in the replacement text are -capitalized. - -If @var{literal} is non-@code{nil}, then @var{replacement} is inserted -exactly as it is, the only alterations being case changes as needed. -If it is @code{nil} (the default), then the character @samp{\} is treated -specially. If a @samp{\} appears in @var{replacement}, then it must be -part of one of the following sequences: - -@table @asis -@item @samp{\&} -@cindex @samp{&} in replacement -@samp{\&} stands for the entire text being replaced. - -@item @samp{\@var{n}} -@cindex @samp{\@var{n}} in replacement -@samp{\@var{n}} stands for the text that matched the @var{n}th -subexpression in the original regexp. Subexpressions are those -expressions grouped inside of @samp{\(@dots{}\)}. @var{n} is a digit. - -@item @samp{\\} -@cindex @samp{\} in replacement -@samp{\\} stands for a single @samp{\} in the replacement text. -@end table - -@code{replace-match} leaves point at the end of the replacement text, -and returns @code{t}. -@end defun - @node Entire Match Data @subsection Accessing the Entire Match Data The functions @code{match-data} and @code{set-match-data} read or write the entire match data, all at once. -@defun match-data -This function returns a newly constructed list containing all the -information on what text the last search matched. Element zero is the -position of the beginning of the match for the whole expression; element -one is the position of the end of the match for the expression. The -next two elements are the positions of the beginning and end of the -match for the first subexpression, and so on. In general, element -@ifinfo +@defun match-data &optional integers reuse reseat +This function returns a list of positions (markers or integers) that +record all the information on what text the last search matched. +Element zero is the position of the beginning of the match for the +whole expression; element one is the position of the end of the match +for the expression. The next two elements are the positions of the +beginning and end of the match for the first subexpression, and so on. +In general, element +@ifnottex number 2@var{n} -@end ifinfo +@end ifnottex @tex number {\mathsurround=0pt $2n$} @end tex corresponds to @code{(match-beginning @var{n})}; and element -@ifinfo +@ifnottex number 2@var{n} + 1 -@end ifinfo +@end ifnottex @tex number {\mathsurround=0pt $2n+1$} @end tex corresponds to @code{(match-end @var{n})}. -All the elements are markers or @code{nil} if matching was done on a -buffer, and all are integers or @code{nil} if matching was done on a -string with @code{string-match}. (In Emacs 18 and earlier versions, -markers were used even for matching on a string, except in the case -of the integer 0.) +Normally all the elements are markers or @code{nil}, but if +@var{integers} is non-@code{nil}, that means to use integers instead +of markers. (In that case, the buffer itself is appended as an +additional element at the end of the list, to facilitate complete +restoration of the match data.) If the last match was done on a +string with @code{string-match}, then integers are always used, +since markers can't point into a string. + +If @var{reuse} is non-@code{nil}, it should be a list. In that case, +@code{match-data} stores the match data in @var{reuse}. That is, +@var{reuse} is destructively modified. @var{reuse} does not need to +have the right length. If it is not long enough to contain the match +data, it is extended. If it is too long, the length of @var{reuse} +stays the same, but the elements that were not used are set to +@code{nil}. The purpose of this feature is to reduce the need for +garbage collection. + +If @var{reseat} is non-@code{nil}, all markers on the @var{reuse} list +are reseated to point to nowhere. As always, there must be no possibility of intervening searches between the call to a search function and the call to @code{match-data} that is @@ -1084,30 +1455,29 @@ intended to access the match data for that search. @end example @end defun -@defun set-match-data match-list +@defun set-match-data match-list &optional reseat This function sets the match data from the elements of @var{match-list}, which should be a list that was the value of a previous call to -@code{match-data}. +@code{match-data}. (More precisely, anything that has the same format +will work.) If @var{match-list} refers to a buffer that doesn't exist, you don't get an error; that sets the match data in a meaningless but harmless way. +If @var{reseat} is non-@code{nil}, all markers on the @var{match-list} list +are reseated to point to nowhere. + @findex store-match-data -@code{store-match-data} is an alias for @code{set-match-data}. +@code{store-match-data} is a semi-obsolete alias for @code{set-match-data}. @end defun @node Saving Match Data @subsection Saving and Restoring the Match Data - All asynchronous process functions (filters and sentinels) and -functions that use @code{recursive-edit} should save and restore the -match data if they do a search or if they let the user type arbitrary -commands. Saving the match data is useful in other cases as -well---whenever you want to access the match data resulting from an -earlier search, notwithstanding another intervening search. - - This example shows the problem that can arise if you fail to -attend to this requirement: + When you call a function that may do a search, you may need to save +and restore the match data around that call, if you want to preserve the +match data from an earlier search for later use. Here is an example +that shows the problem that arises if you fail to save the match data: @example @group @@ -1120,28 +1490,31 @@ attend to this requirement: @end group @end example - In Emacs versions 19 and later, you can save and restore the match -data with @code{save-match-data}: + You can save and restore the match data with @code{save-match-data}: -@defspec save-match-data body@dots{} -This special form executes @var{body}, saving and restoring the match -data around it. This is useful if you wish to do a search without -altering the match data that resulted from an earlier search. -@end defspec +@defmac save-match-data body@dots{} +This macro executes @var{body}, saving and restoring the match +data around it. The return value is the value of the last form in +@var{body}. +@end defmac - You can use @code{set-match-data} together with @code{match-data} to -imitate the effect of the special form @code{save-match-data}. This is -useful for writing code that can run in Emacs 18. Here is how: + You could use @code{set-match-data} together with @code{match-data} to +imitate the effect of the special form @code{save-match-data}. Here is +how: @example @group (let ((data (match-data))) (unwind-protect - @dots{} ; @r{May change the original match data.} + @dots{} ; @r{Ok to change the original match data.} (set-match-data data))) @end group @end example + Emacs automatically saves and restores the match data when it runs +process filter functions (@pxref{Filter Functions}) and process +sentinels (@pxref{Sentinels}). + @ignore Here is a function which restores the match data provided the buffer associated with it still exists. @@ -1167,48 +1540,156 @@ associated with it still exists. @end smallexample @end ignore -@node Searching and Case -@section Searching and Case -@cindex searching and case +@node Search and Replace +@section Search and Replace +@cindex replacement - By default, searches in Emacs ignore the case of the text they are -searching through; if you specify searching for @samp{FOO}, then -@samp{Foo} or @samp{foo} is also considered a match. Regexps, and in -particular character sets, are included: thus, @samp{[aB]} would match -@samp{a} or @samp{A} or @samp{b} or @samp{B}. + If you want to find all matches for a regexp in part of the buffer, +and replace them, the best way is to write an explicit loop using +@code{re-search-forward} and @code{replace-match}, like this: - If you do not want this feature, set the variable -@code{case-fold-search} to @code{nil}. Then all letters must match -exactly, including case. This is a per-buffer-local variable; altering -the variable affects only the current buffer. (@xref{Intro to -Buffer-Local}.) Alternatively, you may change the value of -@code{default-case-fold-search}, which is the default value of -@code{case-fold-search} for buffers that do not override it. +@example +(while (re-search-forward "foo[ \t]+bar" nil t) + (replace-match "foobar")) +@end example - Note that the user-level incremental search feature handles case -distinctions differently. When given a lower case letter, it looks for -a match of either case, but when given an upper case letter, it looks -for an upper case letter only. But this has nothing to do with the -searching functions Lisp functions use. +@noindent +@xref{Replacing Match,, Replacing the Text that Matched}, for a +description of @code{replace-match}. + + However, replacing matches in a string is more complex, especially +if you want to do it efficiently. So Emacs provides a function to do +this. + +@defun replace-regexp-in-string regexp rep string &optional fixedcase literal subexp start +This function copies @var{string} and searches it for matches for +@var{regexp}, and replaces them with @var{rep}. It returns the +modified copy. If @var{start} is non-@code{nil}, the search for +matches starts at that index in @var{string}, so matches starting +before that index are not changed. + +This function uses @code{replace-match} to do the replacement, and it +passes the optional arguments @var{fixedcase}, @var{literal} and +@var{subexp} along to @code{replace-match}. + +Instead of a string, @var{rep} can be a function. In that case, +@code{replace-regexp-in-string} calls @var{rep} for each match, +passing the text of the match as its sole argument. It collects the +value @var{rep} returns and passes that to @code{replace-match} as the +replacement string. The match-data at this point are the result +of matching @var{regexp} against a substring of @var{string}. +@end defun -@defopt case-replace -This variable determines whether @code{query-replace} should preserve -case in replacements. If the variable is @code{nil}, then -@code{replace-match} should not try to convert case. -@end defopt + If you want to write a command along the lines of @code{query-replace}, +you can use @code{perform-replace} to do the work. -@defopt case-fold-search -This buffer-local variable determines whether searches should ignore -case. If the variable is @code{nil} they do not ignore case; otherwise -they do ignore case. -@end defopt +@defun perform-replace from-string replacements query-flag regexp-flag delimited-flag &optional repeat-count map start end +This function is the guts of @code{query-replace} and related +commands. It searches for occurrences of @var{from-string} in the +text between positions @var{start} and @var{end} and replaces some or +all of them. If @var{start} is @code{nil} (or omitted), point is used +instead, and the end of the buffer's accessible portion is used for +@var{end}. -@defvar default-case-fold-search -The value of this variable is the default value for -@code{case-fold-search} in buffers that do not override it. This is the -same as @code{(default-value 'case-fold-search)}. +If @var{query-flag} is @code{nil}, it replaces all +occurrences; otherwise, it asks the user what to do about each one. + +If @var{regexp-flag} is non-@code{nil}, then @var{from-string} is +considered a regular expression; otherwise, it must match literally. If +@var{delimited-flag} is non-@code{nil}, then only replacements +surrounded by word boundaries are considered. + +The argument @var{replacements} specifies what to replace occurrences +with. If it is a string, that string is used. It can also be a list of +strings, to be used in cyclic order. + +If @var{replacements} is a cons cell, @code{(@var{function} +. @var{data})}, this means to call @var{function} after each match to +get the replacement text. This function is called with two arguments: +@var{data}, and the number of replacements already made. + +If @var{repeat-count} is non-@code{nil}, it should be an integer. Then +it specifies how many times to use each of the strings in the +@var{replacements} list before advancing cyclically to the next one. + +If @var{from-string} contains upper-case letters, then +@code{perform-replace} binds @code{case-fold-search} to @code{nil}, and +it uses the @code{replacements} without altering the case of them. + +Normally, the keymap @code{query-replace-map} defines the possible +user responses for queries. The argument @var{map}, if +non-@code{nil}, specifies a keymap to use instead of +@code{query-replace-map}. +@end defun + +@defvar query-replace-map +This variable holds a special keymap that defines the valid user +responses for @code{perform-replace} and the commands that use it, as +well as @code{y-or-n-p} and @code{map-y-or-n-p}. This map is unusual +in two ways: + +@itemize @bullet +@item +The ``key bindings'' are not commands, just symbols that are meaningful +to the functions that use this map. + +@item +Prefix keys are not supported; each key binding must be for a +single-event key sequence. This is because the functions don't use +@code{read-key-sequence} to get the input; instead, they read a single +event and look it up ``by hand.'' +@end itemize @end defvar +Here are the meaningful ``bindings'' for @code{query-replace-map}. +Several of them are meaningful only for @code{query-replace} and +friends. + +@table @code +@item act +Do take the action being considered---in other words, ``yes.'' + +@item skip +Do not take action for this question---in other words, ``no.'' + +@item exit +Answer this question ``no,'' and give up on the entire series of +questions, assuming that the answers will be ``no.'' + +@item act-and-exit +Answer this question ``yes,'' and give up on the entire series of +questions, assuming that subsequent answers will be ``no.'' + +@item act-and-show +Answer this question ``yes,'' but show the results---don't advance yet +to the next question. + +@item automatic +Answer this question and all subsequent questions in the series with +``yes,'' without further user interaction. + +@item backup +Move back to the previous place that a question was asked about. + +@item edit +Enter a recursive edit to deal with this question---instead of any +other action that would normally be taken. + +@item delete-and-edit +Delete the text being considered, then enter a recursive edit to replace +it. + +@item recenter +Redisplay and center the window, then ask the same question again. + +@item quit +Perform a quit right away. Only @code{y-or-n-p} and related functions +use this answer. + +@item help +Display some help, then ask again. +@end table + @node Standard Regexps @section Standard Regular Expressions Used in Editing @cindex regexps used standardly in editing @@ -1218,37 +1699,56 @@ same as @code{(default-value 'case-fold-search)}. used for certain purposes in editing: @defvar page-delimiter -This is the regexp describing line-beginnings that separate pages. The -default value is @code{"^\014"} (i.e., @code{"^^L"} or @code{"^\C-l"}). +This is the regular expression describing line-beginnings that separate +pages. The default value is @code{"^\014"} (i.e., @code{"^^L"} or +@code{"^\C-l"}); this matches a line that starts with a formfeed +character. @end defvar + The following two regular expressions should @emph{not} assume the +match always starts at the beginning of a line; they should not use +@samp{^} to anchor the match. Most often, the paragraph commands do +check for a match only at the beginning of a line, which means that +@samp{^} would be superfluous. When there is a nonzero left margin, +they accept matches that start after the left margin. In that case, a +@samp{^} would be incorrect. However, a @samp{^} is harmless in modes +where a left margin is never used. + @defvar paragraph-separate This is the regular expression for recognizing the beginning of a line that separates paragraphs. (If you change this, you may have to -change @code{paragraph-start} also.) The default value is @code{"^[ -\t\f]*$"}, which is a line that consists entirely of spaces, tabs, and -form feeds. +change @code{paragraph-start} also.) The default value is +@w{@code{"[@ \t\f]*$"}}, which matches a line that consists entirely of +spaces, tabs, and form feeds (after its left margin). @end defvar @defvar paragraph-start This is the regular expression for recognizing the beginning of a line that starts @emph{or} separates paragraphs. The default value is -@code{"^[ \t\n\f]"}, which matches a line starting with a space, tab, -newline, or form feed. +@w{@code{"\f\\|[ \t]*$"}}, which matches a line containing only +whitespace or starting with a form feed (after its left margin). @end defvar @defvar sentence-end -This is the regular expression describing the end of a sentence. (All -paragraph boundaries also end sentences, regardless.) The default value -is: - -@example -"[.?!][]\"')@}]*\\($\\|\t\\| \\)[ \t\n]*" -@end example +If non-@code{nil}, the value should be a regular expression describing +the end of a sentence, including the whitespace following the +sentence. (All paragraph boundaries also end sentences, regardless.) + +If the value is @code{nil}, the default, then the function +@code{sentence-end} has to construct the regexp. That is why you +should always call the function @code{sentence-end} to obtain the +regexp to be used to recognize the end of a sentence. +@end defvar -This means a period, question mark or exclamation mark, followed by a -closing brace, followed by tabs, spaces or new lines. +@defun sentence-end +This function returns the value of the variable @code{sentence-end}, +if non-@code{nil}. Otherwise it returns a default value based on the +values of the variables @code{sentence-end-double-space} +(@pxref{Definition of sentence-end-double-space}), +@code{sentence-end-without-period} and +@code{sentence-end-without-space}. +@end defun -For a detailed explanation of this regular expression, see @ref{Regexp -Example}. -@end defvar +@ignore + arch-tag: c2573ca2-18aa-4839-93b8-924043ef831f +@end ignore