comment on

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
[download]

(Should work on any Perl version 5.8.9+.)

Give a man a fish: <%-{-{-{-<

In reply to Re: regex and substrings by AnomalousMonk
in thread regex and substrings by ovedpo15

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