http://www.perlmonks.org?node_id=1219173


in reply to regex and substrings

Implementing the criteria given by Corion here, and just for completness, here's a single-regex solution. Note that this accepts the empty string as a substring of any non-empty string.

c:\@Work\Perl\monks>perl -le "use warnings; use strict; ;; use Test::More 'no_plan'; use Test::NoWarnings; ;; use constant SUBSTRINGS => ( 'the empty string is a substring of any non-empty string', [ 'x', '' ], [ 'helloworld', '' ], [ 'xx', 'x' ], [ 'xy', 'x' ], [ 'yx', 'x' ], [ 'yxy', 'x' ], [ 'helloworld', 'hello' ], [ 'helloworld', 'world' ], [ 'hellohello', 'hello' ], [ 'hello world', 'hello' ], [ 'hello world', 'world' ], [ 'hello hello', 'hello' ], [ 'xhelloworldx', 'hello' ], [ 'xhelloworldx', 'world' ], [ 'xhello worldx', 'hello' ], [ 'xhello worldx', 'world' ], ); ;; use constant NO_SUBSTRINGS => ( 'the empty string is not a substring of itself', [ '', '' ], [ '', 'x' ], [ 'x', 'x' ], [ 'x', 'xx' ], [ 'x', 'y' ], [ 'foo', 'bar' ], [ 'hello', 'hello' ], [ 'hello', 'xhello' ], [ 'hello', 'hellox' ], [ 'xhello', 'hellox' ], [ 'hello', 'helloworld' ], ); ;; note 'each of these strings has a substring'; VECTOR_SUBSTRING: for my $ar_vector (SUBSTRINGS) { if (not ref $ar_vector) { note $ar_vector; next VECTOR_SUBSTRING; } ;; my ($string, $substring) = @$ar_vector; ;; ok $string =~ m{ \A .+ \Q$substring\E | \Q$substring\E .+ \z }xms, qq{'$string' contains '$substring'}; } ;; note 'none of these strings has a substring'; VECTOR_NO_SUBSTRING: for my $ar_vector (NO_SUBSTRINGS) { if (not ref $ar_vector) { note $ar_vector; next VECTOR_NO_SUBSTRING; } ;; my ($string, $substring) = @$ar_vector; ;; ok $string !~ m{ \A .+ \Q$substring\E | \Q$substring\E .+ \z }xms, qq{'$string' does not contain '$substring'}; } ;; done_testing; ;; exit; " # each of these strings has a substring # the empty string is a substring of any non-empty string ok 1 - 'x' contains '' ok 2 - 'helloworld' contains '' ok 3 - 'xx' contains 'x' ok 4 - 'xy' contains 'x' ok 5 - 'yx' contains 'x' ok 6 - 'yxy' contains 'x' ok 7 - 'helloworld' contains 'hello' ok 8 - 'helloworld' contains 'world' ok 9 - 'hellohello' contains 'hello' ok 10 - 'hello world' contains 'hello' ok 11 - 'hello world' contains 'world' ok 12 - 'hello hello' contains 'hello' ok 13 - 'xhelloworldx' contains 'hello' ok 14 - 'xhelloworldx' contains 'world' ok 15 - 'xhello worldx' contains 'hello' ok 16 - 'xhello worldx' contains 'world' # none of these strings has a substring # the empty string is not a substring of itself ok 17 - '' does not contain '' ok 18 - '' does not contain 'x' ok 19 - 'x' does not contain 'x' ok 20 - 'x' does not contain 'xx' ok 21 - 'x' does not contain 'y' ok 22 - 'foo' does not contain 'bar' ok 23 - 'hello' does not contain 'hello' ok 24 - 'hello' does not contain 'xhello' ok 25 - 'hello' does not contain 'hellox' ok 26 - 'xhello' does not contain 'hellox' ok 27 - 'hello' does not contain 'helloworld' 1..27 ok 28 - no warnings 1..28
(Should work on any Perl version 5.8.9+.)


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