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Diffstat (limited to 'doc/switch.n')
| -rw-r--r-- | doc/switch.n | 138 |
1 files changed, 105 insertions, 33 deletions
diff --git a/doc/switch.n b/doc/switch.n index c454a3d..6e27f56 100644 --- a/doc/switch.n +++ b/doc/switch.n @@ -5,10 +5,8 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: switch.n,v 1.4 1999/09/21 04:20:36 hobbs Exp $ -'\" +.TH switch n 8.5 Tcl "Tcl Built-In Commands" .so man.macros -.TH switch n 7.0 Tcl "Tcl Built-In Commands" .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME @@ -18,7 +16,6 @@ switch \- Evaluate one of several scripts, depending on a given value .sp \fBswitch \fR?\fIoptions\fR?\fI string \fR{\fIpattern body \fR?\fIpattern body \fR...?} .BE - .SH DESCRIPTION .PP The \fBswitch\fR command matches its \fIstring\fR argument against each of @@ -33,25 +30,68 @@ matches \fIstring\fR and no default is given, then the \fBswitch\fR command returns an empty string. .PP If the initial arguments to \fBswitch\fR start with \fB\-\fR then -they are treated as options. The following options are -currently supported: +they are treated as options +unless there are exactly two arguments to \fBswitch\fR (in which case the +first must the \fIstring\fR and the second must be the +\fIpattern\fR/\fIbody\fR list). +The following options are currently supported: .TP 10 \fB\-exact\fR +. Use exact matching when comparing \fIstring\fR to a pattern. This is the default. .TP 10 \fB\-glob\fR +. When matching \fIstring\fR to the patterns, use glob-style matching (i.e. the same as implemented by the \fBstring match\fR command). .TP 10 \fB\-regexp\fR +. When matching \fIstring\fR to the patterns, use regular expression matching (as described in the \fBre_syntax\fR reference page). .TP 10 +\fB\-nocase\fR +. +Causes comparisons to be handled in a case-insensitive manner. +.TP 10 +\fB\-matchvar\fR \fIvarName\fR +. +This option (only legal when \fB\-regexp\fR is also specified) +specifies the name of a variable into which the list of matches +found by the regular expression engine will be written. The first +element of the list written will be the overall substring of the input +string (i.e. the \fIstring\fR argument to \fBswitch\fR) matched, the +second element of the list will be the substring matched by the first +capturing parenthesis in the regular expression that matched, and so +on. When a \fBdefault\fR branch is taken, the variable will have the +empty list written to it. This option may be specified at the same +time as the \fB\-indexvar\fR option. +.TP 10 +\fB\-indexvar\fR \fIvarName\fR +. +This option (only legal when \fB\-regexp\fR is also specified) +specifies the name of a variable into which the list of indices +referring to matching substrings +found by the regular expression engine will be written. The first +element of the list written will be a two-element list specifying the +index of the start and index of the first character after the end of +the overall substring of the input +string (i.e. the \fIstring\fR argument to \fBswitch\fR) matched, in a +similar way to the \fB\-indices\fR option to the \fBregexp\fR can +obtain. Similarly, the second element of the list refers to the first +capturing parenthesis in the regular expression that matched, and so +on. When a \fBdefault\fR branch is taken, the variable will have the +empty list written to it. This option may be specified at the same +time as the \fB\-matchvar\fR option. +.TP 10 \fB\-\|\-\fR +. Marks the end of options. The argument following this one will be treated as \fIstring\fR even if it starts with a \fB\-\fR. +This is not required when the matching patterns and bodies are grouped +together in a single argument. .PP Two syntaxes are provided for the \fIpattern\fR and \fIbody\fR arguments. The first uses a separate argument for each of the patterns and commands; @@ -68,9 +108,12 @@ no command or variable substitutions are performed on them; this makes the behavior of the second form different than the first form in some cases. .PP -If a \fIbody\fR is specified as ``\fB\-\fR'' it means that the \fIbody\fR +If a \fIbody\fR is specified as +.QW \fB\-\fR +it means that the \fIbody\fR for the next pattern should also be used as the body for this -pattern (if the next pattern also has a body of ``\fB\-\fR'' +pattern (if the next pattern also has a body of +.QW \fB\-\fR then the body after that is used, and so on). This feature makes it possible to share a single \fIbody\fR among several patterns. @@ -78,37 +121,66 @@ several patterns. Beware of how you place comments in \fBswitch\fR commands. Comments should only be placed \fBinside\fR the execution body of one of the patterns, and not intermingled with the patterns. +.SH "EXAMPLES" +.PP +The \fBswitch\fR command can match against variables and not just +literals, as shown here (the result is \fI2\fR): .PP -Below are some examples of \fBswitch\fR commands: .CS -\fBswitch\0abc\0a\0\-\0b\0{format 1}\0abc\0{format 2}\0default\0{format 3}\fR +set foo "abc" +\fBswitch\fR abc a \- b {expr {1}} $foo {expr {2}} default {expr {3}} .CE -will return \fB2\fR, +.PP +Using glob matching and the fall-through body is an alternative to +writing regular expressions with alternations, as can be seen here +(this returns \fI1\fR): +.PP .CS -\fBswitch\0\-regexp\0aaab { - ^a.*b$\0\- - b\0{format 1} - a*\0{format 2} - default\0{format 3} -}\fR +\fBswitch\fR \-glob aaab { + a*b \- + b {expr {1}} + a* {expr {2}} + default {expr {3}} +} .CE -will return \fB1\fR, and +.PP +Whenever nothing matches, the \fBdefault\fR clause (which must be +last) is taken. This example has a result of \fI3\fR: +.PP +.CS +\fBswitch\fR xyz { + a \- + b { + # Correct Comment Placement + expr {1} + } + c { + expr {2} + } + default { + expr {3} + } +} +.CE +.PP +When matching against regular expressions, information about what +exactly matched is easily obtained using the \fB\-matchvar\fR option: +.PP .CS -\fBswitch\0xyz { - a - \- - b - { - # Correct Comment Placement - format 1 - } - a* - {format 2} - default - {format 3} -}\fR +\fBswitch\fR \-regexp \-matchvar foo \-\- $bar { + a(b*)c { + puts "Found [string length [lindex $foo 1]] 'b's" + } + d(e*)f(g*)h { + puts "Found [string length [lindex $foo 1]] 'e's and\e + [string length [lindex $foo 2]] 'g's" + } +} .CE -will return \fB3\fR. - +.SH "SEE ALSO" +for(n), if(n), regexp(n) .SH KEYWORDS switch, match, regular expression +.\" Local Variables: +.\" mode: nroff +.\" End: |