71 lines
3.2 KiB
Factor
71 lines
3.2 KiB
Factor
! Copyright (C) 2009 Daniel Ehrenberg
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! See http://factorcode.org/license.txt for BSD license.
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USING: help.syntax help.markup regexp strings ;
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IN: regexp.combinators
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ABOUT: "regexp.combinators"
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ARTICLE: "regexp.combinators.intro" "Regular expression combinator rationale"
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"Regular expression combinators are useful when part of the regular expression contains user input. For example, given a sequence of strings on the stack, a regular expression which matches any one of them can be constructed:"
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{ $code
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"[ <literal> ] map <or>"
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}
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"Without combinators, a naive approach would look as follows:"
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{ $code
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"\"|\" join <regexp>"
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}
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"However, this code is incorrect, because one of the strings in the sequence might contain characters which have special meaning inside a regular expression. Combinators avoid this problem by building a regular expression syntax tree directly, without any parsing." ;
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ARTICLE: "regexp.combinators" "Regular expression combinators"
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"The " { $vocab-link "regexp.combinators" } " vocabulary defines combinators which can be used to build up regular expressions to match strings. This complements the traditional syntax defined in the " { $vocab-link "regexp" } " vocabulary."
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{ $subsection "regexp.combinators.intro" }
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"Basic combinators:"
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{ $subsection <literal> }
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{ $subsection <nothing> }
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"Higher-order combinators for building new regular expressions from existing ones:"
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{ $subsection <or> }
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{ $subsection <and> }
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{ $subsection <not> }
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{ $subsection <sequence> }
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{ $subsection <zero-or-more> }
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"Derived combinators implemented in terms of the above:"
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{ $subsection <one-or-more> }
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"Setting options:"
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{ $subsection <option> } ;
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HELP: <literal>
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{ $values { "string" string } { "regexp" regexp } }
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{ $description "Creates a regular expression which matches the given literal string." } ;
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HELP: <nothing>
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{ $values { "value" regexp } }
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{ $description "The empty regular language." } ;
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HELP: <or>
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{ $values { "regexps" "a sequence of regular expressions" } { "disjunction" regexp } }
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{ $description "Creates a new regular expression which matches the union of what elements of the sequence match." } ;
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HELP: <and>
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{ $values { "regexps" "a sequence of regular expressions" } { "conjunction" regexp } }
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{ $description "Creates a new regular expression which matches the intersection of what elements of the sequence match." } ;
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HELP: <sequence>
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{ $values { "regexps" "a sequence of regular expressions" } { "regexp" regexp } }
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{ $description "Creates a new regular expression which matches strings that match each element of the sequence in order." } ;
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HELP: <not>
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{ $values { "regexp" regexp } { "not-regexp" regexp } }
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{ $description "Creates a new regular expression which matches everything that the given regexp does not match." } ;
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HELP: <one-or-more>
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{ $values { "regexp" regexp } { "regexp+" regexp } }
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{ $description "Creates a new regular expression which matches one or more copies of the given regexp." } ;
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HELP: <option>
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{ $values { "regexp" regexp } { "regexp?" regexp } }
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{ $description "Creates a new regular expression which matches zero or one copies of the given regexp." } ;
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HELP: <zero-or-more>
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{ $values { "regexp" regexp } { "regexp*" regexp } }
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{ $description "Creates a new regular expression which matches zero or more copies of the given regexp." } ;
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