Regexp::Optimizer(3pm) User Contributed Perl Documentation Regexp::Optimizer(3pm)
NAME
Regexp::Optimizer - optimizes regular expressions
SYNOPSIS
use Regexp::Optimizer;
my $o = Regexp::Optimizer->new;
my $re = $o->optimize(qr/foobar|fooxar|foozap/);
# $re is now qr/foo(?:[bx]ar|zap)/
ABSTRACT
This module does, ahem, attempts to, optimize regular expressions.
INSTALLATION
To install this module type the following:
perl Makefile.PL
make
make test
make install
DESCRIPTION
Here is a quote from perltodo.
Factoring out common suffices/prefices in regexps (trie optimization)
Currently, the user has to optimize "foo|far" and "foo|goo" into "f(?:oo|ar)" and "[fg]oo" by hand; this could be done automatically.
This module implements just that.
EXPORT
Since this is an OO module there is no symbol exported.
METHODS
This module is implemented as a subclass of Regexp::List. For methods not listed here, see Regexp::List.
$o = Regexp::Optimizer->new;
$o->set(key => value, ...)
Just the same us Regexp::List except for the attribute below;
unexpand
When set to one, $o->optimize() tries to $o->expand before actually starting the operation.
# cases you need to set expand => 1
$o->set(expand => 1)->optimize(qr/
foobar|
fooxar|
foozar
/x);
$re = $o->optimize(regexp);
Does the job. Note that unlike "->list2re()" in Regexp::List, the argument is the regular expression itself. What it basically does
is to find groups will alterations and replace it with the result of "$o->list2re".
$re = $o->list2re(list of words ...)
Same as "list2re()" in Regexp::List in terms of functionality but how it tokenize "atoms" is different since the arguments can be
regular expressions, not just strings. Here is a brief example.
my @expr = qw/foobar fooba+/;
Regexp::List->new->list2re(@expr) eq qr/fooba[+r]/;
Regexp::Optimizer->new->list2re(@expr) eq qr/foob(?:a+ar)/;
CAVEATS
This module is still experimental. Do not assume that the result is the same as the unoptimized version.
o When you just want a regular expression which matches normal words with not metacharacters, use <Regexp::List>. It's more robus and
much faster.
o When you have a list of regular expessions which you want to aggregate, use "list2re" of THIS MODULE.
o Use "->optimize()" when and only when you already have a big regular expression with alterations therein.
"->optimize()" does support nested groups but its parser is not tested very well.
BUGS
o Regex parser in this module (which itself is implemented by regular expression) is not as thoroughly tested as Regexp::List
o May still fall into deep recursion when you attempt to optimize deeply nested regexp. See "PRACTICALITY".
o Does not grok (?{expression}) and (?(cond)yes|no) constructs yet
o You need to escape characters in character classes.
$o->optimize(qr/[a-z()]|[A-Z]/); # wrong
$o->optimize(qr/[a-z()]|[A-Z]/); # right
$o->optimize(qr/[0-9A-Za-z]|[Q-_.!~*"'()E]/ # right, too.
o When character(?: class(?:es)?)? are aggregated, duplicate ranges are left as is. Though functionally OK, it is cosmetically ugly.
$o->optimize(qr/[0-5]|[5-9]|0123456789/);
# simply turns into [0-5][5-9]0123456789] not [0-9]
I left it that way because marking-rearranging approach can result a humongous result when unicode characters are concerned (and
p{Properties}).
PRACTICALITY
Though this module is still experimental, It is still good enough even for such deeply nested regexes as the followng.
# See 3.2.2 of http://www.ietf.org/rfc/rfc2616.txt
# BNF faithfully turned into a regex
http://(?:(?:(?:(?:(?:[a-z]|[A-Z])|[0-9])|(?:(?:[a-z]|[A-Z])|[0-9])(?:(?:(?:[a-z]|[A-Z])|[0-9])|-)*(?:(?:[a-z]|[A-Z])|[0-9])).)*(?:(?:[a-z]|[A-Z])|(?:[a-z]|[A-Z])(?:(?:(?:[a-z]|[A-Z])|[0-9])|-)*(?:(?:[a-z]|[A-Z])|[0-9])).?|[0-9]+.[0-9]+.[0-9]+.[0-9]+)(?::[0-9]*)?(?:/(?:(?:(?:(?:[a-z]|[A-Z])|[0-9])|[-\_.!~*'()])|%(?:[0-9]|[A-Fa-f])(?:[0-9]|[A-Fa-f])|[:@&=+$,])*(?:;(?:(?:(?:(?:[a-z]|[A-Z])|[0-9])|[-\_.!~*'()])|%(?:[0-9]|[A-Fa-f])(?:[0-9]|[A-Fa-f])|[:@&=+$,])*)*(?:/(?:(?:(?:(?:[a-z]|[A-Z])|[0-9])|[-\_.!~*'()])|%(?:[0-9]|[A-Fa-f])(?:[0-9]|[A-Fa-f])|[:@&=+$,])*(?:;(?:(?:(?:(?:[a-z]|[A-Z])|[0-9])|[-\_.!~*'()])|%(?:[0-9]|[A-Fa-f])(?:[0-9]|[A-Fa-f])|[:@&=+$,])*)*)*(?:\?(?:[;/?:@&=+$,]|(?:(?:(?:[a-z]|[A-Z])|[0-9])|[-\_.!~*'()])|%(?:[0-9]|[A-Fa-f])(?:[0-9]|[A-Fa-f]))*)?)?
# and optimized
http://(?::?[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?.[a-zA-Z]*(?:[a-zA-Z0-9-]*[a-zA-Z0-9])?.?|[0-9]+.[0-9]+.[0-9]+.[0-9]+)(?::[0-9]*)?(?:/(?:(?:(?:[a-zA-Z0-9-\_.!~*'x28x29]|%[0-9A-Fa-f][0-9A-Fa-f])|[:@&=+$,]))*(?:;(?:(?:(?:[a-zA-Z0-9-\_.!~*'x28x29]|%[0-9A-Fa-f][0-9A-Fa-f])|[:@&=+$,]))*)*(?:/(?:(?:(?:[a-zA-Z0-9-\_.!~*'x28x29]|%[0-9A-Fa-f][0-9A-Fa-f])|[:@&=+$,]))*(?:;(?:(?:(?:[a-zA-Z0-9-\_.!~*'x28x29]|%[0-9A-Fa-f][0-9A-Fa-f])|[:@&=+$,]))*)*)*(?:\?(?:(?:[;/?:@&=+$,a-zA-Z0-9-\_.!~*'x28x29]|%[0-9A-Fa-f][0-9A-Fa-f]))*)?)?
By carefully examine both you can find that character classes are properly aggregated.
SEE ALSO
Regexp::List -- upon which this module is based
"eg/" directory in this package contains example scripts.
Perl standard documents
L<perltodo>, L<perlre>
CPAN Modules
Regexp::Presuf, Text::Trie
Books
Mastering Regular Expressions <http://www.oreilly.com/catalog/regex2/>
AUTHOR
Dan Kogai <dankogai@dan.co.jp>
COPYRIGHT AND LICENSE
Copyright 2003 by Dan Kogai
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
perl v5.14.2 2004-12-05 Regexp::Optimizer(3pm)