source: project/wiki/regex-literals @ 4785

[[tags: eggs literals regex regex-literals]]

[[toc:]]

== Introduction

A reader extension providing precompiled regular expression literals of the
form <code>#/[a-z0-9]+/i</code> and <code>#r{^/path/(to)/file$}</code>.


== Examples

=== Using regular expression literals in the interpreter

Loading {{regex-literals}} also loads the {{regex}} unit and allows
convenient use of regular expression literals as follows:

<enscript highlight=scheme>#;1> (use regex-literals)

#;2> #/[A-Za-z0-9]+/
#<regexp>

#;3> ,x #/^[a-z0-9]+$/i
(regexp "^[a-z0-9]+$" #t #f #f)

#;4> (string-match #/^(\d{2}):(\d{2})(..)/ "11:59pm")
("11:59pm" "11" "59" "pm")

#;5> (string-split-fields #/[^\s]+/ "the quick brown fox jumps over the lazy dog")
("the" "quick" "brown" "fox" "jumps" "over" "the" "lazy" "dog")

#;6> (string-split-fields #r{[^/]+} "/path/to/file")
("path" "to" "file")

#;7> (string-substitute #/(\w+)\s+(\w+)/u "\\2, \\1" "John Smith")
"Smith, John"

</enscript>


=== Using regular expression literals with the compiler

Passing a {{-X regex-literals}} command-line option to {{csc}} allows you to
conveniently make use of regular expression literals in your egg or compiled
program without making the {{regex-literals}} egg a runtime dependency.

(See the [[php-s11n]] egg for an example of building with {{regex-literals}}.)


== Authors

[[Arto Bendiken]], [[http://3e8.org/zb|Zbigniew]]


== Requires

* [[Unit regex|regex]]


== Reader extensions

This egg installs a reader extension for {{#\/}} that reads a regular
expression literal as described below in {{read-regex-literal}}, and another
reader extension for {{#\r}} that works similarly but supports a generalized
delimiter syntax as described in {{read-regex-literal/general}}.

Note that there are some caveats to using reader extensions when compiling;
for more details, refer to the relevant
[[faq#Why%20does%20{{define-reader-ctor}}%20not%20work%20in%20my%20compiled%20program?|FAQ entry]].


== Input and output

=== read-regex-literal

 [procedure] (read-regex-literal [PORT])

Reads a regular expression literal of the form {{#/.../}} from {{PORT}},
which defaults to the value of {{(current-input-port)}}. The literal is
converted to a precompiled regular expression object using the {{(regexp)}}
procedure provided by the [[Unit regex|regex]] unit.

Regular expression literals may include one or more options that modify the
way the pattern matches strings. The options are one or more characters
placed immediately after the terminator:

* {{#/.../i}} PCRE_CASELESS: case-insensitive mode; the pattern match will
  ignore the case of letters in the pattern.
* {{#/.../x}} PCRE_EXTENDED: extended mode; complex regular expressions can
  be difficult to read, so this option allows you to insert spaces,
  newlines, and comments in the pattern to make it more readable.
* {{#/.../u}} PCRE_UTF8: UTF-8 mode; sets the language encoding of the
  regular expression.


=== read-regex-literal/general

 [procedure] (read-regex-literal/general [PORT])

Reads a regular expression literal of the form {{#r(...)}} from {{PORT}},
which defaults to the value of {{(current-input-port)}}. This works
otherwise similarly to {{read-regex-literal}} but supports a generalized
delimiter syntax as follows:

* Matching delimiter pairs: {{#r{...}}}, {{#r(...)}}, {{#r[...]}} and
  {{#r<...>}}
* Any arbitrary character: {{#r!...!}}, {{#r|...|}}, {{#r@...@}}, and so
  forth.


== License

  Copyright (c) 2006-2007 Arto Bendiken.
  
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to
  deal in the Software without restriction, including without limitation the
  rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
  sell copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
  
  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  IN THE SOFTWARE.


== Version history

;1.0.2 : Support for generalized {{#r(...)}} delimiters (by [[http://3e8.org/zb|Zbigniew]])
;1.0.1 : Added support for the {{#/.../i}}, {{#/.../x}} and {{#/.../u}} options.
;1.0.0 : Initial release of the {{regex-literals}} egg.