Comparison of regular expression engines

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This is a comparison of regular expression engines.

Libraries

List of regular expression libraries
Name Official website Programming language Software license Used by
Boost.Regex[Note 1]:{{{3}}} Boost C++ Libraries C++ Boost  
Boost.Xpressive Boost C++ Libraries C++ Boost  
CL-PPCRE Edi Weitz Common Lisp BSD  
cppre Jeff Stuart C++ GPL  
DEELX RegExLab C++ Free personal and commercial use  
FREJ[Note 2]:{{{3}}} Fuzzy Regular Expressions for Java Java LGPL  
GLib/GRegex[Note 3]:{{{3}}} Marco Barisione C LGPL  
GRETA Microsoft Research C++ ?  
ICU International Components for Unicode C, C++[Note 4]:{{{3}}} ICU  
Jakarta/Regexp The Apache Jakarta Project Java Apache  
java.util.regex Java's User manual Java Java license jEdit
JRegex JRegex Java BSD  
Oniguruma Kosako C BSD Atom, Take Command Console, Tera Term, TextMate, Sublime Text and SubEthaEdit
Pattwo Stevesoft Java (compatible with Java 1.0) LGPL  
PCRE pcre.org C, C++[Note 5]:{{{3}}} BSD Nginx, Julia, HHVM, Notepad++
Qt/QRegExp Digia C++ Qt GNU GPL v. 3.0,

Qt GNU LGPL v. 2.1, Qt Commercial

 Kate, Kile
regex - Henry Spencer's regular expression libraries ArgList C BSD  
RE2 RE2 C++ BSD  
Henry Spencer's Advanced Regular Expressions Tcl C BSD  
TRE[Note 2]:{{{3}}} Ville Laurikari C BSD  
TPerlRegEx TPerlRegEx VCL Component Object Pascal MPLv1.1  
TRegExpr RegExp Studio Object Pascal Dual-license: freeware, or LGPL with static linking exception  
RGX RGX C++ based component library P6R  
XRegExp XRegExp JavaScript MIT  
Wolfram Language (Mathematica) Wolfram Language Documentation Center Wolfram Language Mathematica, the Wolfram Development Platform
  1. ↑ Formerly called Regex++
  2. ↑ 2.0 2.1 One of fuzzy regular expression engines
  3. ↑ Included since version 2.13.0
  4. ↑ ICU4J, the Java version, does not support regular expressions.
  5. ↑ C++ bindings were developed by Google and became officially part of PCRE in 2006.

Languages

List of languages and frameworks including regular expression support
Language Official website Software license Remarks
.NET MSDN MIT License[Note 1]:{{{3}}}[Note 2]:{{{3}}}
POSIX C (C) libc/regex from BSD BSD According to regex(3), available from at least 4.4BSD (if not earlier)
C++11 (C++) C++ standards website ? Since ISO14822:2011(e)
D D Boost Software License[Note 3]:{{{3}}}
Go Golang.org BSD-style
Haskell Haskell.org BSD3 Omitted in the language report, and in GHC's Hierarchical Libraries
Java Java GNU General Public License REs are written as strings in source code: all backslashes must be doubled, harming readability.
JavaScript (ECMAScript) ECMA-262 BSD3 Limited but REs are first-class citizens of the language with a specific /.../mod syntax.
Julia JuliaLang.org MIT License REs are part of the language core library using PCRE built-in and an optional wrapper for (C code) ICU is available.
Lua Lua.org MIT License Uses simplified, limited dialect; can be bound to more powerful library, like PCRE or an alternative parser like LPeg.
Mathematica Wolfram Proprietary
Free Pascal (Object Pascal) www.freepascal.org LGPL with static linking exception Free Pascal 2.6+ ships with TRegExpr from Sorokin and two other regular expression libraries; See wiki.lazarus.freepascal.org/Regexpr.
Cocoa (Objective-C) Apple Proprietary As of 2012, available on only iOS 4+ and OS X 10.7+
OCaml Caml LGPL
Perl Perl.com Artistic License, or GNU General Public License Full, central part of the language
PHP PHP.net PHP License Has two implementations, with PCRE being the more efficient in speed, functions
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 and 1.9 use different engines; 1.9 integrates Oniguruma.
SAP ABAP SAP.com Proprietary
Tcl tcl.tk Tcl/Tk License
(BSD-style)		 Tcl library doubles as a regular expression library.
ActionScript 3 ActionScript Technology Center Free
Wolfram Language Wolfram Research Proprietary; usable for free on a limited scale on the Wolfram Development platform.
  1. ↑ https://github.com/dotnet/corefx/blob/7116584186f8f3a886616aaf8cb5d4a982c60e27/src/System.Text.RegularExpressions/src/System/Text/RegularExpressions/Regex.cs#L2
  2. ↑ https://github.com/dotnet/corefx#license
  3. ↑ http://www.digitalmars.com/d/2.0/phobos/std_regex.html

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.

Part 1

Language feature comparison (part 1)
"+" quantifier Negated character classes Non-greedy quantifiers[Note 1]:{{{3}}} Shy groups[Note 2]:{{{3}}} Recursion Look-ahead Look-behind Backreferences[Note 3]:{{{3}}} >9 indexable captures
Boost.Regex Yes Yes Yes Yes Yes[Note 4]:{{{3}}} Yes Yes Yes Yes
Boost.Xpressive Yes Yes Yes Yes Yes[Note 5]:{{{3}}} 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]:{{{3}}} No Some[Note 6]:{{{3}}} 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
ICU Regex Yes Yes Yes Yes No Yes Yes Yes Yes
Java Yes Yes Yes Yes No Yes Yes Yes Yes
JavaScript (ECMAScript) Yes Yes Yes Yes No Yes No Yes Yes
JGsoft Yes Yes Yes Yes No Yes Yes Yes Yes
Lua Yes Yes Some[Note 7]:{{{3}}} No No No No Yes No
.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 Yes[Note 8]:{{{3}}} Yes Yes Yes Yes
Qt/QRegExp Yes Yes Yes Yes No Yes No Yes Yes
R[Note 9]:{{{3}}} Yes Yes Yes Yes No Yes Yes 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 7.4b.000 (2013-07-28) [±] Yes Yes Yes Yes No Yes Yes Yes No
RGX Yes Yes Yes Yes No Yes Yes Yes Yes
Tcl Yes Yes Yes Yes No Yes Yes Yes Yes
TRegExpr Yes ? Yes ? ? ? ? ? ?
XRegExp Yes Yes Yes Yes No Yes No Yes Yes
  1. ↑ 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.
  2. ↑ 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.
  3. ↑ 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".
  4. ↑ 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
  5. ↑ 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
  6. ↑ 6.0 6.1 FREJ have no repetitive quantifiers, but have "optional" element which behaves similar to simple "?" quantifier.
  7. ↑ Lua's only non-greedy quantifier is -, which is a non-greedy version of *. It does not have non-greedy versions of + or ?; in the former case, the non-greedy effect can be achieved by repeating the token followed by -, but in the latter case, there is no equivalent.
  8. ↑ Supported by the optional regex library only.
  9. ↑ Regular Expressions as used in R

Part 2

Language feature comparison (part 2)
Directives[Note 1]:{{{3}}} Conditionals Atomic groups[Note 2]:{{{3}}} Named capture[Note 3]:{{{3}}} Comments Embedded code Unicode property support [1] Balancing groups[Note 4]:{{{3}}} Variable-length look-behinds[Note 5]:{{{3}}}
Boost.Regex Yes Yes Yes Yes Yes No Some[Note 6]:{{{3}}} No No
Boost.Xpressive Yes No Yes Yes Yes No No No No
CL-PPCRE Yes Yes Yes Yes Yes Yes Some[Note 6]:{{{3}}} No No
EmEditor Yes Yes ? ? Yes No ? No No
FREJ No No Yes Yes Yes No ? No No
GLib/GRegex Yes Yes Yes Yes Yes No Some[Note 6]:{{{3}}} No No
GNU grep Yes Yes ? Yes Yes No No No No
Haskell ? ? ? ? ? No No No No
ICU Regex Yes No Yes No Yes No Yes No No
Java Yes No Yes Yes[Note 7]:{{{3}}} Yes No Some[Note 6]:{{{3}}} No No
JavaScript (ECMAScript) No No No No No No No No No
JGsoft Yes Yes Yes Yes Yes No Some[Note 6]:{{{3}}} No Yes
Lua No No No No No No No No No
.NET Yes Yes Yes Yes Yes No Some[Note 6]:{{{3}}} Yes Yes
OCaml No No No No No No No No No
OmniOutliner 3.6.2 ? ? ? ? No No ? No No
PCRE Yes Yes Yes Yes Yes Yes Yes No No
Perl Yes Yes Yes Yes Yes Yes Yes No No
PHP Yes Yes Yes Yes Yes No No No No
Python Yes Yes Yes[Note 8]:{{{3}}} Yes Yes No Yes[Note 9]:{{{3}}} No Yes[Note 8]:{{{3}}}
Qt/QRegExp No No No No No No No No No
RE2 Yes No  ? Yes No No Some[Note 6]:{{{3}}} No No
Ruby Yes No Yes Yes Yes Yes Some[Note 6]:{{{3}}} No No
Tcl Yes No Yes No Yes No Yes No No
TRE Yes No No No Yes No ? No No
Vim Yes No Yes No No No No No Yes
RGX Yes Yes Yes Yes Yes No Yes No No
XRegExp Leading only No No Yes Yes No Yes No No
  1. ↑ Also known as Flags modifiers or Option letters. Example pattern: "(?i:test)".
  2. ↑ Also called Independent sub-expressions
  3. ↑ Similar to back references but with names instead of indices
  4. ↑ Special feature allowing to match balanced constructs without recursion
  5. ↑ Refers to the possibility of including quantifiers in look-behinds, thus making their length unpredictable
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 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.
  7. ↑ Available as of JDK7
  8. ↑ 8.0 8.1 Supported by the optional regex library only.
  9. ↑ May only be available in the regex library when used with Python versions after 3.3

API features

API feature comparison
Native UTF-16 support[Note 1]:{{{3}}} Native UTF-8 support[Note 1]:{{{3}}} Multi-line matching Partial match[Note 2]:{{{3}}}
Boost.Regex No No Yes Yes
GLib/GRegex Yes Yes Yes ?
ICU Regex Yes No Yes ?
Java No Partial[Note 3]:{{{3}}} Yes Yes
.NET No[Note 4]:{{{3}}} Yes Yes ?
PCRE Yes[Note 5]:{{{3}}} Yes Yes Yes
Qt/QRegExp Yes No No ?
Tcl Yes Yes[Note 6]:{{{3}}} Yes ?
TRE No ? Yes ?
RGX No No Yes ?
wxWdigets::wxRegEx[Note 7]:{{{3}}} Yes Yes Yes ?
XRegExp Yes ? Yes ?
  1. ↑ 1.0 1.1 Means the format can be used internally without explicit conversion.
  2. ↑ Partial match of the whole regular expression. For example the pattern ".*END$" will match any string partially, but only strings ending with END fully.[1]
  3. ↑ Supports Unicode 4.0 standard from 2003; latest plans for JDK7 include Unicode 6.0 (2011) support.[2]
  4. ↑ 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.[3].
  5. ↑ Since version 8.30
  6. ↑ Tcl includes facilities to convert to and from UTF-8.
  7. ↑ wxRegEx uses any system supplied POSIX library or if not available and for Unicode mode uses Henry Spencer's library.

See also

References

  1. ↑ http://www.unicode.org/reports/tr18/

External links

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