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Boost.RegexStandards Conformance |
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Boost.regex is intended to conform to the regular expression standardization proposal, which will appear in a future C++ standard technical report (and hopefully in a future version of the standard).
All of the ECMAScript regular expression syntax features are supported, except that:
Negated class escapes (\S, \D and \W) are not permitted inside character class definitions ( [...] ).
The escape sequence \u matches any upper case character (the same as [[:upper:]]) rather than a Unicode escape sequence; use \x{DDDD} for Unicode escape sequences.
Almost all Perl features are supported, except for:
| (?{code}) | Not implementable in a compiled strongly typed language. |
| (??{code}) | Not implementable in a compiled strongly typed language. |
All the POSIX basic and extended regular expression features are supported, except that:
No character collating names are recognized except those specified in the POSIX standard for the C locale, unless they are explicitly registered with the traits class.
Character equivalence classes ( [[=a=]] etc) are probably buggy except on Win32. Implementing this feature requires knowledge of the format of the string sort keys produced by the system; if you need this, and the default implementation doesn't work on your platform, then you will need to supply a custom traits class.
The following comments refer to Unicode Technical Standard #18: Unicode Regular Expressions version 9.
| # | Feature | Support |
| 1.1 | Hex Notation | Yes: use \x{DDDD} to refer to code point UDDDD. |
| 1.2 | Character Properties | All the names listed under the General Category Property are supported. Script names and Other Names are not currently supported. |
| 1.3 | Subtraction and Intersection |
Indirectly support by forward-lookahead: (?=[[:X:]])[[:Y:]] Gives the intersection of character properties X and Y. (?![[:X:]])[[:Y:]] Gives everything in Y that is not in X (subtraction). |
| 1.4 | Simple Word Boundaries | Conforming: non-spacing marks are included in the set of word characters. |
| 1.5 | Caseless Matching | Supported, note that at this level, case transformations are 1:1, many to many case folding operations are not supported (for example "ß" to "SS"). |
| 1.6 | Line Boundaries | Supported, except that "." matches only one character of "\r\n". Other than that word boundaries match correctly; including not matching in the middle of a "\r\n" sequence. |
| 1.7 | Code Points | Supported: provided you use the u32* algorithms, then UTF-8, UTF-16 and UTF-32 are all treated as sequences of 32-bit code points. |
| 2.1 | Canonical Equivalence | Not supported: it is up to the user of the library to convert all text into the same canonical form as the regular expression. |
| 2.2 | Default Grapheme Clusters | Not supported. |
| 2.3 | Not supported. | |
| 2.4 | Not Supported. | |
| 2.5 | Name Properties | Supported: the expression "[[:name:]]" or \N{name} matches the named character "name". |
| 2.6 | Wildcard properties | Not Supported. |
| 3.1 | Tailored Punctuation. | Not Supported. |
| 3.2 | Tailored Grapheme Clusters | Not Supported. |
| 3.3 | Tailored Word Boundaries. | Not Supported. |
| 3.4 | Tailored Loose Matches | Partial support: [[=c=]] matches characters with the same primary equivalence class as "c". |
| 3.5 | Tailored Ranges | Supported: [a-b] matches any character that collates in the range a to b, when the expression is constructed with the collate flag set. |
| 3.6 | Context Matches | Not Supported. |
| 3.7 | Incremental Matches | Supported: pass the flag match_partial to the regex algorithms. |
| 3.8 | Unicode Set Sharing | Not Supported. |
| 3.9 | Possible Match Sets | Not supported, however this information is used internally to optimise the matching of regular expressions, and return quickly if no match is possible. |
| 3.10 | Folded Matching | Partial Support: It is possible to achieve a similar effect by using a custom regular expression traits class. |
| 3.11 | Custom Submatch Evaluation | Not Supported. |
Revised 28 June 2004
© Copyright John Maddock 1998- 2004
Use, modification and distribution are subject to the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
