Comparison of regular expression engines

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[edit] Libraries

List of regular expression libraries
	Official website	Programming language	Software license
Boost.Regex ^{[Note 1]}	Boost C++ Libraries	C++	Boost Software License
Boost.Xpressive	Boost C++ Libraries	C++	Boost Software License
CL-PPCRE	Edi Weitz	Common Lisp	BSD
cppre	Jeff Stuart	C++	GPL
DEELX	RegExLab	C++	"free for personal use and commercial use"
FREJ ^{[Note 2]}	Fuzzy Regular Expressions for Java	Java	LGPL
GLib/GRegex ^{[Note 3]}	Marco Barisione	C	LGPL
GRETA	Microsoft Research	C++	?
ICU	International Components for Unicode	C/C++/Java	ICU license
Jakarta/Regexp	The Apache Jakarta Project	Java	Apache License
JRegex	JRegex	Java	BSD
Oniguruma	Kosako	C	BSD
Pattwo	Stevesoft	Java (compatible with Java 1.0)	LGPL
PCRE	Philip Hazel	C/C++^{[Note 4]}	BSD
Qt/QRegExp	[3]	C++	Qt GNU GPL v. 3.0 / Qt GNU LGPL v. 2.1 / Qt Commercial
regex - Henry Spencer's regular expression libraries	ArgList	C	BSD
re2	Google Code	C++	BSD
TRE ^{[Note 2]}	Ville Laurikari	C	BSD
TPerlRegEx	TPerlRegEx VCL Component	Object Pascal	MPLv1.1
TRegExpr	RegExp Studio	Object Pascal	double licensed: Freeware or LGPL with static linking exception
RGX	RGX	C++ based component library	P6R license

^ formerly called Regex++
^ ^a ^b one of fuzzy regular expression engines
^ included since version 2.13.0
^ C++ bindings were developed by Google and became officially part of PCRE in 2006

[edit] Languages

List of languages and frameworks coming with regular expression support
Language	Official website	Software license	Remarks
.NET	MSDN	Proprietary
C++			since ISO14822:2011(e)
D	D	Boost Software License^{[Note 1]}
Go	Golang.org	BSD-style license
Haskell	Haskell.org	BSD3	Not included in the language report; nor in GHC's Hierarchical Libraries
Java	Java	GNU General Public License	REs are written as strings in source code (all backslashes must be doubled, hurting readability).
JavaScript/ECMAScript		?	Limited but REs are first-class citizens of the language with a specific `/.../mod` syntax.
Lua	Lua.org	MIT License	Uses a simplified, limited dialect. Can be bound to a more powerful library, like PCRE or an alternative parser like LPeg.
Object Pascal (Free Pascal)	www.freepascal.org	LGPL with static linking exception	Free Pascal 2.6+ ships with TRegExpr from Sorokin as well as with 2 other regular expression libraries. See http://wiki.lazarus.freepascal.org/Regexpr
Objective-C (Cocoa)	Apple	Proprietary	Currently only available on iOS 4+ and OS X 10.7+
OCaml	Caml	LGPL
Perl	Perl.com	Artistic License or the GNU General Public License	Full, central part of the language.
PHP	PHP.net	PHP License	Has two implementations, with PCRE being the more efficient (speed, functionalities).
Python	python.org	Python Software Foundation License
Ruby	ruby-doc.org	GNU Library General Public License	Ruby 1.8 and 1.9 use different engines; Ruby 1.9 integrates Oniguruma.
SAP ABAP	SAP.com	?
Tcl 8.4	tcl.tk	Tcl/Tk License (Permissive, similar to BSD)
ActionScript 3	?	?

^ http://www.digitalmars.com/d/2.0/phobos/std_regex.html

[edit] Language features

NOTE: An application using a library for regular expression support does not necessarily offer the full set of features of the library, e.g. GNU Grep which uses PCRE does not offer lookahead support, though PCRE does.

[edit] Part 1

Language feature comparison (part 1)
	"+" quantifier	Negated character classes	Non-greedy quantifiers^{[Note 1]}	Shy groups^{[Note 2]}	Recursion	Lookahead	Lookbehind	Backreferences^{[Note 3]}	>9 indexable captures
Boost.Regex	Yes	Yes	Yes	Yes	Yes ^{[Note 4]}	Yes	Yes	Yes	Yes
Boost.Xpressive	Yes	Yes	Yes	Yes	Yes ^{[Note 5]}	Yes	Yes	Yes	Yes
CL-PPCRE	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes
EmEditor	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	No
FREJ	No ^{[Note 6]}	No	Some ^{[Note 6]}	Yes	No	No	No	Yes	Yes
GLib/GRegex	Yes	?	Yes	?	No	?	?	?	?
GNU Grep	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	?
Haskell	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes
Java	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes
ICU Regex	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes
JGsoft	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes
.NET	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes
OCaml	Yes	Yes	No	No	No	No	No	Yes	No
OmniOutliner 3.6.2	Yes	Yes	Yes	No	No	No	No	?	?
PCRE	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Perl	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
PHP	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Python	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes
Qt/QRegExp	Yes	Yes	Yes	Yes	No	Yes	No	Yes	Yes
re2	Yes	Yes	Yes	Yes	No	No	No	No	Yes
Ruby	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
TRE	Yes	Yes	Yes	Yes	No	No	No	Yes	No
Vim 7.3a (2010-05-24)	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	No
RGX	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes
TRegExpr	Yes	?	Yes	?	?	?	?	?	?

^ Non-greedy quantifiers match as few characters as possible, instead of the default as many. Note that many older, pre-POSIX engines were non-greedy and didn't have greedy quantifiers at all
^ Shy groups, also called non-capturing groups cannot be referred to with backreferences; non-capturing groups are used to speed up matching where the groups content needs not be accessed later.
^ Backreferences enable referring to previously matched groups in later parts of the regex and/or replacement string (where applicable). For instance, ([ab]+)\1 matches "abab" but not "abaab"
^ http://www.boost.org/doc/libs/1_47_0/libs/regex/doc/html/boost_regex/syntax/perl_syntax.html#boost_regex.syntax.perl_syntax.recursive_expressions
^ http://www.boost.org/doc/libs/1_47_0/doc/html/xpressive/user_s_guide.html#boost_xpressive.user_s_guide.grammars_and_nested_matches.embedding_a_regex_by_reference
^ ^a ^b FREJ have no repetitive quantifiers, but have "optional" element which behaves similar to simple "?" quantifier

[edit] Part 2

Language feature comparison (part 2)
	Directives ^{[Note 1]}	Conditionals	Atomic groups ^{[Note 2]}	Named capture ^{[Note 3]}	Comments	Embedded code	Unicode property support [4]
Boost.Regex	Yes	Yes	Yes	Yes	Yes	No	Some ^{[Note 4]}
Boost.Xpressive	Yes	No	Yes	Yes	Yes	No	No
CL-PPCRE	Yes	Yes	Yes	Yes	Yes	Yes	No
EmEditor	Yes	Yes	?	?	Yes	No	?
FREJ	No	No	Yes	Yes	Yes	No	?
GLib/GRegex	Yes	Yes	Yes	Yes	Yes	No	Some ^{[Note 4]}
GNU Grep	Yes	Yes	?	Yes	Yes	No	No
Haskell	?	?	?	?	?	No	No
Java	Yes	No	Yes	Yes ^{[Note 5]}	No	No	Some ^{[Note 4]}
ICU Regex	Yes	No	Yes	No	Yes	No	Yes
JGsoft	Yes	Yes	Yes	Yes	Yes	No	Some ^{[Note 4]}
.NET	Yes	Yes	Yes	Yes	Yes	No	Some ^{[Note 4]}
OCaml	No	No	No	No	No	No	No
OmniOutliner 3.6.2	?	?	?	?	No	No	?
PCRE	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Perl	Yes	Yes	Yes	Yes	Yes	Yes	Yes
PHP	Yes	Yes	Yes	Yes	Yes	No	No
Python	Yes	Yes	No	Yes	Yes	No	No
Qt/QRegExp	No	No	No	No	No	No	No
re2	Yes	No	?	Yes	No	No	Some ^{[Note 4]}
Ruby	Yes	No	Yes	Yes	Yes	Yes	Some ^{[Note 4]}
TRE	Yes	No	No	No	Yes	No	?
Vim	Yes	No	Yes	No	No	No	No
RGX	Yes	Yes	Yes	Yes	Yes	No	Yes

^ Also known as Flags modifiers or Option letters. Example pattern: "(?i:test)"
^ Also called Independent sub-expressions
^ Similar to back references but with names instead of indices
^ ^a ^b ^c ^d ^e ^f ^g Unicode property support may be incomplete (products are continuously updated!). **All will be incomplete** when a new Unicode revision is released *until* they are updated to comply.
^ Available as of JDK7.

[edit] API features

API feature comparison
	Native UTF-16 support ^{[Note 1]}	Native UTF-8 support ^{[Note 1]}	Multi-line matching
Boost.Regex	No	No	Yes
GLib/GRegex	Yes	Yes	Yes
ICU Regex	Yes	No	Yes
Java	No	Partial ^{[Note 2]}	Yes
.NET	No ^{[Note 3]}	No	Yes
PCRE	No	Yes	Yes
Qt/QRegExp	Yes	No	No
TRE	No	?	Yes
RGX	No	No	Yes

^ ^a ^b Means the format can be used internally without explicit conversion
^ Supports Unicode 4.0 standard from 2003; latest plans for JDK7 include Unicode 6.0 (2011) support [1]
^ Implementation uses original UCS-2 support/features, so it only recognizes 64K chars total (vs UTF-16's 1,112,064 characters). A Microsoft developer-representative answered a bug report on this as "will not fix" in 2010). [2].

[edit] See also

List of regular expression software

[edit] External links

Regular Expression Flavor Comparison — Detailed comparison of the most popular regular expression flavors
Regexp Syntax Summary

[boost_regex_formerly_regex-0] rmerly called Regex++

[fuzzy_regexp_libraries-1] uzzy regular expression engines

[glib_gregex_version-2] uded since version 2.13.0

[pcre_cpp-3] C++ bindings were developed by Google and became officially part of PCRE in 2006

[boost_mars-8] ttp://www.digitalmars.com/d/2.0/phobos/std_regex.html

[non_greedy-10] Non-greedy quantifiers match as few characters as possible, instead of the default as many. Note that many older, pre-POSIX engines were non-greedy and didn't have greedy quantifiers at all

[shy-11] Shy groups, also called non-capturing groups cannot be referred to with backreferences; non-capturing groups are used to speed up matching where the groups content needs not be accessed later.

[backref-12] Backreferences enable referring to previously matched groups in later parts of the regex and/or replacement string (where applicable). For instance, ([ab]+)\1 matches "abab" but not "abaab"

[boost_regex_recursion-13] ttp://www.boost.org/doc/libs/1_47_0/libs/regex/doc/html/boost_regex/syntax/perl_syntax.html#boost_regex.syntax.perl_syntax.recursive_expressions

[xpressive_recursion-14] ttp://www.boost.org/doc/libs/1_47_0/doc/html/xpressive/user_s_guide.html#boost_xpressive.user_s_guide.grammars_and_nested_matches.embedding_a_regex_by_reference

[frej_non_greedy-15] FREJ have no repetitive quantifiers, but have "optional" element which behaves similar to simple "?" quantifier

[directives_explanation-22] Also known as Flags modifiers or Option letters. Example pattern: "(?i:test)"

[atomic_grouping_explanation-23] Also called Independent sub-expressions

[named_groups_explanation-24] Similar to back references but with names instead of indices

[properties_limited-25] ^ ^a ^b ^c ^d ^e ^f ^g Unicode property support may be incomplete (products are continuously updated!). **All will be incomplete** when a new Unicode revision is released *until* they are updated to comply.

[available_java_7-26] Available as of JDK7.

[unicode_native-32] Means the format can be used internally without explicit conversion

[Partial_Uni4-33] Supports Unicode 4.0 standard from 2003; latest plans for JDK7 include Unicode 6.0 (2011) support [1]

[UCS2-34] Implementation uses original UCS-2 support/features, so it only recognizes 64K chars total (vs UTF-16's 1,112,064 characters). A Microsoft developer-representative answered a bug report on this as "will not fix" in 2010). [2].

[Note 1]

[Note 2]

[Note 3]

[Note 4]

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Comparison of regular expression engines

Contents

[edit] Libraries

[edit] Languages

[edit] Language features

[edit] Part 1

[edit] Part 2

[edit] API features

[edit] See also

[edit] External links

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