FAQ 4.21 How do I remove consecutive pairs of characters?
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From: PerlFAQ Server on 30 May 2010 12:00 This is an excerpt from the latest version perlfaq4.pod, which comes with the standard Perl distribution. These postings aim to reduce the number of repeated questions as well as allow the community to review and update the answers. The latest version of the complete perlfaq is at http://faq.perl.org . -------------------------------------------------------------------- 4.21: How do I remove consecutive pairs of characters? (contributed by brian d foy) You can use the substitution operator to find pairs of characters (or runs of characters) and replace them with a single instance. In this substitution, we find a character in "(.)". The memory parentheses store the matched character in the back-reference "\1" and we use that to require that the same thing immediately follow it. We replace that part of the string with the character in $1. s/(.)\1/$1/g; We can also use the transliteration operator, "tr///". In this example, the search list side of our "tr///" contains nothing, but the "c" option complements that so it contains everything. The replacement list also contains nothing, so the transliteration is almost a no-op since it won't do any replacements (or more exactly, replace the character with itself). However, the "s" option squashes duplicated and consecutive characters in the string so a character does not show up next to itself my $str = 'Haarlem'; # in the Netherlands $str =~ tr///cs; # Now Harlem, like in New York -------------------------------------------------------------------- The perlfaq-workers, a group of volunteers, maintain the perlfaq. They are not necessarily experts in every domain where Perl might show up, so please include as much information as possible and relevant in any corrections. The perlfaq-workers also don't have access to every operating system or platform, so please include relevant details for corrections to examples that do not work on particular platforms. Working code is greatly appreciated. If you'd like to help maintain the perlfaq, see the details in perlfaq.pod. |