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*matchit.txt* Extended "%" matching For instructions on installing this file, type :help add-local-help inside Vim. For Vim version 6.0. Last change: 2001 Jul 28 VIM REFERENCE MANUAL by Benji Fisher *matchit* *matchit.vim* 1. Extended matching with "%" |matchit-intro| 2. Activation |matchit-activate| 3. Configuration |matchit-configure| 4. Supporting a New Language |matchit-newlang| The functionality mentioned here is a plugin, see |add-plugin|. This plugin is only available if 'compatible' is not set. You can avoid loading this plugin by setting the "loaded_matchit" variable in your |vimrc| file: > :let loaded_matchit = 1 {Vi does not have any of this} ============================================================================== 1. Extended matching with "%" *matchit-intro* *matchit-%* % Cycle forward through matching groups, such as "if", "else", "endif", as specified by |b:match_words|. *g%* g% Cycle backwards through matching groups, as specified by |b:match_words|. For example, go from "endif" to "else" to "if". *[%* [% Go to [count] previous unmatched group, as specified by |b:match_words|. Similar to |[{|. *]%* ]% Go to [count] next unmatched group, as specified by |b:match_words|. Similar to |]}|. In Vim, as in plain vi, the percent key, |%|, jumps the cursor from a brace, bracket, or paren to its match. This can be configured with the 'matchpairs' option. The matchit plugin extends this in several ways: You can match whole words, such as "if" and "endif", not just single characters. You can also specify a |regular-expression|. You can define groups with more than two words, such as "if", "else", "endif". Banging on the "%" key will cycle from the "if" to the first "else", the next "else", ..., the closing "endif", and back to the opening "if". Nested structures are skipped. Using |g%| goes in the reverse direction. By default, words inside comments and strings are ignored, unless the cursor is inside a comment or string when you type "%". If the only thing you want to do is modify the behavior of "%" so that it behaves this way, you can > :let b:match_words = &matchpairs < See |matchit-details| for details on what the script does, and |b:match_words| for how to specify matching patterns. LANGUAGES: *matchit-languages* Currently, the following languages are supported: Ada, ASP with VBS, Csh, DTD, Entity, Essbase, Fortran, HTML, JSP (same as HTML), LaTeX, Lua, Pascal, SGML, Shell, Tcsh, Vim, XML. Other languages may already have support via |filetype-plugin|s. To support a new language, see |matchit-newlang| below. DETAILS: *matchit-details* *matchit-parse* Here is an outline of what matchit.vim does each time you hit the "%" key. If there are |backref|s in |b:match_words| then the first step is to produce a version in which these back references have been eliminated; if there are no |backref|s then this step is skipped. This step is called parsing. For example, "$foo\|bar$:end\1" is parsed to yield "$foo\|bar$:end$foo\|bar$". This can get tricky, especially if there are nested groups. If debugging is turned on, the parsed version is saved as |b:match_pat|. *matchit-choose* Next, the script looks for a word on the current line that matches the pattern just constructed. It includes the patterns from the 'matchpairs' option. Unfortunately, deciding which match to choose is a little complicated. The script follows these rules: Insist on a match that ends on or after the cusor. Prefer a match that includes the cursor position (that is, one that starts on or before the cursor). Prefer a match that starts as close to the cursor as possible. Prefer a match in |b:match_words| to a match in 'matchpairs'. If more than one pattern in |b:match_words| matches, choose the one that is listed first. Examples: Suppose you > :let b:match_words = '<,>:<tag>,</tag>' < and hit "%" with the cursor on or before the "<" in "a <tag> is born". The pattern '<' comes first, so it is preferred over '<tag>', which also matches. If the cursor is on the "t", however, then '<tag>' is preferred, because this matches a bit of text containing the cursor. If the two groups of patterns were reversed then '<' would never be preferred. Suppose you > :let b:match_words = 'if,end if' < (Note the space!) and hit "%" with the cursor at the end of "end if". Then "if" matches, which is probably not what you want, but if the cursor starts on the "end " then "end if" is chosen. (You can avoid this problem by using a more complicated pattern.) If there is no match, the script falls back on the usual behavior of |%|. If debugging is turned on, the matched bit of text is saved as |b:match_match| and the cursor column of the start of the match is saved as |b:match_col|. Next, the script looks through |b:match_words| (original and parsed versions) for the group and pattern that match. If debugging is turned on, the group is saved as |b:match_ini| (the first pattern) and |b:match_tail| (the rest). If there are |backref|s then, in addition, the matching pattern is saved as |b:match_word| and a table of translations is saved as |b:match_table|. If there are |backref|s, these are determined from the matching pattern and |b:match_match| and substituted into each pattern in the matching group. The script decides whether to search forwards or backwards and chooses arguments for the |searchpair()| function. Then, the cursor is moved to the start of the match, and |searchpair()| is called. By default, matching structures inside strings and comments are ignored. This can be changed by setting |b:match_skip|. ============================================================================== 2. Activation *matchit-activate* You can use this script as a plugin, by copying it to your plugin directory. See |add-global-plugin| for instructions. You can also add a line to your |vimrc| file, such as > :source $VIMRUNTIME/macros/matchit.vim < Either way, the script should start working the next time you start up Vim. The script does nothing unless it finds a |buffer-variable| named |b:match_words|. The script contains autocommands that set this variable for various file types: see |matchit-languages| above. For a new language, you can add autocommands to the script or to your vimrc file, but the recommended method is to add a line such as > let b:match_words = '\<foo\>:\<bar\>' < to the |filetype-plugin| for your language. See |b:match_words| below for how this variable is interpreted. TROUBLESHOOTING *matchit-troubleshoot* The script should work in most installations of Vim. It may not work if Vim was compiled with a minimal feature set, for example if the |+syntax| option was not enabled. If your Vim has support for syntax compiled in, but you do not have |syntax| highlighting turned on, matchit.vim should work, but it may fail to skip matching groups in comments and strings. If the |filetype| mechanism is turned off, the |b:match_words| variable will probably not be defined automatically. ============================================================================== 3. Configuration *matchit-configure* There are several variables (and one highlight group) that govern the behavior of matchit.vim. Note that these are variables local to the buffer, not options, so use |:let| to define them, not |:set|. Some of these variables have values that matter; for others, it only matters whether the variable has been defined. All of these can be defined in the autocommand that defines |b:match_words| or "on the fly." The main variable is |b:match_words|. It is described in the section below on supporting a new language. *MatchError* *matchit-hl* *matchit-highlight* MatchError is the highlight group for error messages from the script. By default, it is linked to WarningMsg. If you do not want to be bothered by error messages, you can define this to be something invisible. For example, if you use the GUI version of Vim and your command line is normally white, you can do > :hi MatchError guifg=white guibg=white < *b:match_ignorecase* If you > :let b:match_ignorecase = 1 < then matchit.vim acts as if 'ignorecase' is set: for example, "end" and "END" are equivalent. If you > :let b:match_ignorecase = 0 < then matchit.vim treats "end" and "END" differently. (There will be no b:match_infercase unless someone requests it.) *b:match_debug* Define b:match_debug if you want debugging information to be saved. See |matchit-debug|, below. *b:match_skip* If b:match_skip is defined, it is passed as the skip argument to |searchpair()|. This controls when matching structures are skipped, or ignored. By default, they are ignored inside comments and strings, as determined by the |syntax| mechanism. (If syntax highlighting is turned off, nothing is skipped.) You can set b:match_skip to a string, which evaluates to a non-zero, numerical value if the match is to be skipped or zero if the match should not be skipped. In addition, the following special values are supported by matchit.vim: s:foo becomes (current syntax item) =~ foo S:foo becomes (current syntax item) !~ foo r:foo becomes (line before cursor) =~ foo R:foo becomes (line before cursor) !~ foo (The "s" is meant to suggest "syntax", and the "r" is meant to suggest "regular expression".) Examples: You can get the default behavior with > :let b:match_skip = 's:comment\|string' < If you want to skip matching structures unless they are at the start of the line (ignoring whitespace) then you can > :let b:match_skip = 'R:^\s*' < Do not do this if strings or comments can span several lines, since the normal syntax checking will not be done if you set b:match_skip. In LaTeX, since "%" is used as the comment character, you can > :let b:match_skip = 'r:%' < Unfortunately, this will skip anything after "\%", an escaped "%". To allow for this, and also "\\%" (an excaped backslash followed by the comment character) you can > :let b:match_skip = 'r:$^\|[^\\]$$\\\\$*%' < ============================================================================== 4. Supporting a New Language *matchit-newlang* *b:match_words* In order for matchit.vim to support a new language, you must define a suitable pattern for |b:match_words|. You may also want to set some of the |matchit-configure| variables, as described above. If your language has a complicated syntax, or many keywords, you will need to know something about Vim's |regular-expression|s. The format for |b:match_words| is similar to that of the 'matchpairs' option: it is a comma (,)-separated list of groups; each group is a colon(:)-separated list of patterns (regular expressions). It is OK to have only one group; the effect is undefined if a group has only one pattern. A simple example is > :let b:match_words = '\<if\>:\<endif\>,' \ . '\<while\>:\<continue\>:\<break\>:\<endwhile\>' < (In Vim regular expressions, |\<| and |\>| denote word boundaries. Thus "if" matches the end of "endif" but "\<if\>" does not.) Then banging on the "%" key will bounce the cursor between "if" and the matching "endif"; and from "while" to any matching "continue" or "break", then to the matching "endwhile" and back to the "while". It is almost always easier to use |literal-string|s (single quotes) as above: '\<if\>' rather than "\\<if\\>" and so on. Once you have defined the appropriate value of |b:match_words|, you will probably want to have this set automatically each time you edit the appropriate file type. The recommended way to do this is by adding the definition to a |filetype-plugin| file. Be careful that your initial pattern does not match your final pattern. See the example above for the use of word-boundary expressions. It is usually better to use ".\{-}" (as many as necessary) instead of ".*" (as many as possible). See |\{-|. For example, in the string "<tag>label</tag>", "<.*>" matches the whole string whereas "<.\{-}>" and "<[^>]*>" match "<tag>" and "</tag>". *matchit-spaces* *matchit-s:notend* If "if" is to be paired with "end if" (Note the space!) then word boundaries are not enough. Instead, define a regular expression notend that will match anything but "end" and use it as follows: > :let s:notend = '\%(\<end\s\+\)\@<!' :let b:match_words = notend . '\<if\>,\<end\s\+if\>' < *matchit-s:sol* This is a simplified version of what is done for Ada. The s:notend is a |script-variable|. Similarly, you may want to define a start-of-line regular expression > :let s:sol = '\%(^\|;\)\s*' < if keywords are only recognized after the start of a line or after a semicolon (;), with optional white space. *matchit-backref* *matchit-\1* In any group, the expressions |\1|, |\2|, ..., |\9| refer to parts of the INITIAL pattern enclosed in |$|escaped parentheses|$|. These are referred to as back references, or backrefs. For example, > :let b:match_words = '\<b$o\+$\>,$h$\1\>' < means that "bo" pairs with "ho" and "boo" pairs with "hoo" and so on. Note that "\1" does not refer to the "$h$" in this example. If you have "$nested \(parentheses$\) then "\d" refers to the d-th "$" and everything up to and including the matching "$": in "$nested\(parentheses$\)", "\1" refers to everything and "\2" refers to "$parentheses$". If you use a variable such as |s:notend| or |s:sol| in the previous paragraph then remember to count any "$" patterns in this variable. You do not have to use groups defined by |\%($|. It should be possible to resolve back references from any pattern in the group. For example, > :let b:match_words = '$foo$$bar$:more\1:and\2:end\1\2' < would not work because "\2" cannot be determined from "morefoo" and "\1" cannot be determined from "andbar". On the other hand, > :let b:match_words = '$\(foo$$bar$\):\3\2:end\1' < should work (and have the same effect as "foobar:barfoo:endfoobar"), although this has not been thoroughly tested. You can use |zero-width| patterns such as |\@<=| and |\zs|. (The latter has not been thouroughly tested in matchit.vim.) For example, if the keyword "if" must occur at the start of the line, with optional white space, you might use the pattern "$^\s*$\@<=if" so that the cursor will end on the "i" instead of at the start of the line. For another example, if HTML had only one tag then one could > :let b:match_words = '<,>:<\@<=tag>,<\@<=/tag>' < so that "%" can bounce between matching "<" and ">" pairs or (starting on "tag" or "/tag") between matching tags. Without the |\@<=|, the script would bounce from "tag" to the "<" in "</tag>", and another "%" would not take you back to where you started. DEBUGGING *matchit-debug* *:MatchDebug* If you are having trouble figuring out the appropriate definition of |b:match_words| then you can take advantage of the same information I use when debugging the script. This is especially true if you are not sure whether your patterns or my script are at fault! To make this more convenient, I have made the command :MatchDebug, which defines the variable |b:match_debug| and creates a Matchit menu. This menu makes it convenient to check the values of the variables described below. You will probably also want to read |matchit-details| above. Defining the variable |b:match_debug| causes the script to set the following variables, each time you hit the "%" key. Several of these are only defined if |b:match_words| includes |backref|s. *b:match_pat* The b:match_pat variable is set to |b:match_words| with |backref|s parsed. *b:match_match* The b:match_match variable is set to the bit of text that is recognized as a match. *b:match_col* The b:match_col variable is set to the cursor column of the start of the matching text. *b:match_wholeBR* The b:match_wholeBR variable is set to the comma-separated group of patterns that matches, with |backref|s unparsed. *b:match_iniBR* The b:match_iniBR variable is set to the first pattern in |b:match_wholeBR|. *b:match_ini* The b:match_ini variable is set to the first pattern in |b:match_wholeBR|, with |backref|s resolved from |b:match_match|. *b:match_tail* The b:match_tail variable is set to the remaining patterns in |b:match_wholeBR|, with |backref|s resolved from |b:match_match|. *b:match_word* The b:match_word variable is set to the pattern from |b:match_wholeBR| that matches |b:match_match|. *b:match_table* The back reference '\'.d refers to the same thing as '\'.b:match_table[d] in |b:match_word|. KNOWN BUGS AND LIMITATIONS *matchit-bugs* Just because I know about a bug does not mean that it is on my todo list. I try to respond to reports of bugs that cause real problems. If it does not cause serious problems, or if there is a work-around, a bug may sit there for a while. Moral: if a bug (known or not) bothers you, let me know. It would be nice if "\0" were recognized as the entire pattern. That is, it would be nice if "foo:\end\0" had the same effect as "$foo$:\end\1". I may try to implement this in a future version. (This is not so easy to arrange as you might think!) ============================================================================== vim:tw=78:fo=tcq2: