Perl - Generate All Matching String To A Regex

Question

I am kinda new in perl, i wanted to know if there is a way for generating all the combinations that matches a regex.

how is the best way to generate all the matching strings to :

05[0,2,4,7][\d]{7}

thanks in advance.

I agree with Kendall Frey's comment below, you are probably trying to do something the wrong way, so you should probably try to describe your main problem situation. — TLP, May 19 '12 at 14:27
This is a frequently asked question. I downvoted this for lack of research. - Edit: and indeed, it has come up on SO before: http://stackoverflow.com/questions/4208733/generative-regular-expressions http://stackoverflow.com/questions/4605289/listing-all-patterns-that-a-regex-matches — daxim, May 19 '12 at 14:53
maybe you should learn something about regular languages and other stuff about formal grammatics? — gaussblurinc, May 19 '12 at 14:57

score 5 · Answer 1 · answered May 19 '12 at 14:22

While you cannot just take any regex and produce any strings it might fit, in this case you can easily adapt and overcome.

You can use glob to generate combinations:

perl -lwe "print for glob '05{0,2,4,7}'"
050
052
054
057

However, I should not have to tell you that \d{7} actually means quite a few million combinations, right? Generating a list of numbers is trivial, formatting them can be done with sprintf:

my @nums = map sprintf("%07d", $_), 0 .. 9_999_999;

That is assuming you are only looking for 0-9 numericals.

Take those nums and combine them with the globbed ones: Tada.

score 4 · Accepted Answer · answered May 19 '12 at 13:27

4

No there is no way to generate all matches for a certain regex. Consider this one:

a+

There is an infinite number of matches for that regex, thus you cannot list them all.

By the way, I think you want your regex to look like this:

05[0247]\d{7}

answered May 19 '12 at 13:27

Kendall Frey

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Thanks,what is the efficient way of generating these strings? – RonenIL May 19 '12 at 14:13
1

You will need to use something other than a regex, since regexes are too flexible. Also, *there is no efficient way*. The best you can get is exponential time. I don't know what your problem is, but I'd guess there is a good chance you are doing it wrong. – Kendall Frey May 19 '12 at 14:21
there is no problem, i just want to generate all these number for testing purposes. – RonenIL May 21 '12 at 06:42

score 3 · Answer 3 · edited Aug 09 '17 at 03:50

3

2012 answer

String::Random
Regexp::Genex - generates random strings that match the regexp; not all the possible strings, even for finite patterns like [class]
Parse::RandGen
§6.5 regex string generation in HOP

edited Aug 09 '17 at 03:50

Dan Dascalescu

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answered May 19 '12 at 14:53

daxim

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score 1 · Answer 4 · answered May 20 '12 at 04:53

1

Then there is a way to generate all (four billion of) the matches for this certain regex, viz., 05[0247]\d{7}:

use Modern::Perl;

for my $x (qw{0 2 4 7}) {
    say "05$x" . sprintf '%07d', $_ for 0 .. 9999999;
}

answered May 20 '12 at 04:53

Kenosis

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Perl - Generate All Matching String To A Regex

4 Answers4

2012 answer