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The W3C defines the HTML standard, CSS standard, and some other standards. I know there are other groups who define standards as well. Who defines the syntax of regular expressions?
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@Nick Pierpoint: "Regular expressions are "regular" because they are defined by a finite set of symbols - a formal language." THIS IS WRONG. Regular expressions easily define infinite languages.
A regular expression can be defined as a language or string accepted by a finite automata.
Regex has its own terminologies, conditions, and syntax; it is, in a sense, a mini programming language. Regex can be used to add, remove, isolate, and manipulate all kinds of text and data. It could be used as a simple text editor command, e.g., search and replace, or as it's own powerful text-processing language.
Regular Expressions describe exactly the regular languages. If E is a regular expression, then L(E) is the regular language it defines. For each regular expression E, we can create a DFA A such that L(E) = L(A).
Regular expressions are covered by several standard bodies, including IEEE standard 1003.1 (so called Posix): http://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap09.html
However, there are plenty of other approaches to regular expression syntax, the other popular one being Perl (PCRE). For a nice overview of all major regular expression implementations, including extensions, check out this useful resource: http://www.regular-expressions.info/tools.html
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Regular expressions originated from unix and are a part of the Perl language. If a regular expression language is similar to Perl's regular expressions, it is called Perl Compatible Regular Expressions (PCRE)
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answered Oct 19 '22 07:10
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