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Regular expressions are used in search engines, in search and replace dialogs of word processors and text editors, in text processing utilities such as sed and AWK, and in lexical analysis. Regular expressions are supported in many programming languages. Library implementations are often called an "engine", [4] [5] and many of these are ...
Python: python.org: Python Software Foundation License: Python has two major implementations, the built in re and the regex library. Ruby: ruby-doc.org: GNU Library General Public License: Ruby 1.8, Ruby 1.9, and Ruby 2.0 and later versions use different engines; Ruby 1.9 integrates Oniguruma, Ruby 2.0 and later integrate Onigmo, a fork from ...
Complex regular expressions can often be constructed in several different ways, all with the same outputs but with greatly varying efficiency. If AWB is taking a long time to generate results because of a regex rule: Try constructing the expression a different way. There are several online resources with guidance to creating efficient regex ...
Besides the built-in RE/flex POSIX regex pattern matcher, RE/flex also supports PCRE2, Boost.Regex and std::regex pattern matching libraries. PCRE2 and Boost.Regex offer a richer regular expression pattern syntax with Perl pattern matching semantics, but are slower due to their intrinsic NFA-based matching algorithm.
The RE2 algorithm has been rewritten in Rust as the package "regex". CloudFlare's web application firewall uses this package because the RE2 algorithm is immune to ReDoS. [8] Russ Cox also wrote RE1, an earlier regular expression based on a bytecode interpreter. [9] OpenResty uses a RE1 fork called "sregex". [10]
An incomplete history of the QED Text Editor by Dennis Ritchie - provides the history of regular expressions in computer programs; The Implementation of Functional Programming Languages, pages 53–103 Simon Peyton Jones, published by Prentice Hall, 1987. Nemerle, pattern matching. Erlang, pattern matching. Prop: a C++ based pattern matching ...
To decide whether two given regular expressions describe the same language, each can be converted into an equivalent minimal deterministic finite automaton via Thompson's construction, powerset construction, and DFA minimization. If, and only if, the resulting automata agree up to renaming of states, the regular expressions' languages agree.
Sed regular expressions, particularly those using the "s" operator, are much similar to Perl (sed is a predecessor to Perl). The default delimiter is "/", but any delimiter can be used; the default is s / regexp / replacement / , but s : regexp : replacement : is also a valid form.