Perl-compatible regular expression optimizer ## 0. Contents This is the documentation of regex-opt-1.2.2.
| 1\. [Purpose](#h0) 2\. [Usage](#h1) 3\. [Supported syntax](#h2) 4\. [Unsupported syntax](#h3) | 5\. [Optimizations performed](#h4) 6\. [Optimizations not performed](#h5) 7\. [Copying](#h6) 8\. [Requirements](#h7) 9\. [Downloading](#download) |
Optimizes perl-compatible regular expressions.
The general syntax for running the program is: `regex-opt ` Example: `regex-opt 'xaz|xbz|xcz' x[a-c]z` Try running regex-opt on [Abigail](http://www.foad.org/%7Eabigail/)'s 7 kilobyte [URL regexp](http://www.foad.org/~abigail/Perl/url3.regex). The result should be about 5 kilobytes long.
* * (repeat 0-inf) * + (repeat 1-inf) * ? (repeat 0-1) * {n} (repeat n) * {n,} (repeat n-inf) * {n,m} (repeat n-m) * . (accept any char except \n) * [a-z] (character sets) * [^a-z] (inverse character sets) * [[:alpha:]] (character classes) * \s (and other character classes and escapes) * x|y (alternatives) * (?:x|y) (non-capturing grouping) * *? (non-greedy repeat)
* ^ (match string-begin) * $ (match string-end) * () (capturing is converted to noncapturing) * Any (? -command that is not mentioned in supported syntax * Unicode-specific markup
* Character set optimization: [A-Zabcdefgh-yz0-9%] becomes [[:alnum:]%] * Alternate characters: y|[yp]|[zx] becomes [px-z] * Counting: aaa* and aa+ become a{2,} and (a?){3} becomes a{0,3} * Combining: abcde|xycde becomes (?:ab|xy)cde * Parenthesis reduction: ((abc)) becomes abc, (xx|yy)|zz becomes xx|yy|zz * Compression: xyzyzxyzyz becomes (?:x(?:yz){2}){2} * This might not be always a good thing. * Choice counting: a+|aa+ becomes a+, (b|) becomes b?, dxxxxb|dxxxb|dxxb|dxb becomes dx{1,4}b
* Combining counts: * a?|b? should become (?:a|b)?, now becomes a?|b? * Redundancy removal (removal of alternatives that are subsets of other alternatives): * xfooy|x[a-q]+y should become x[a-q]+y, now becomes x(?:foo|[a-q]+)y Help in solving these shortcomings would be welcome.
regex-opt has been written by Joel Yliluoma, a.k.a. [Bisqwit](http://iki.fi/bisqwit/), and is distributed under the terms of the [General Public License](http://www.gnu.org/licenses/licenses.html#GPL) (GPL).
For compiling you need the following GNU tools: g++, make.
The official home page of regex-opt is at [http://iki.fi/bisqwit/source/regex-opt.html](http://iki.fi/bisqwit/source/regex-opt.html). Check there for new versions.
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