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Re: Retain first 4 characters of a string

by Anonymous Monk
on Aug 24, 2012 at 09:05 UTC ( #989457=note: print w/ replies, xml ) Need Help??


in reply to Retain first 4 characters of a string

Sure, if you can start writing that program, I'll finish it for you


Comment on Re: Retain first 4 characters of a string
Re^2: Retain first 4 characters of a string
by perlnoobster (Sexton) on Aug 24, 2012 at 09:15 UTC
    Hello anon monk :) I've conjured up the following and am trying to work with it:  my $trim = join ' ', (split /\s+/, $phn)[0..1]; it retains the word and not the first characters of each word though :( Please can you help?

      And here it is, a bunch

      #!/usr/bin/perl -- use strict; use warnings; use 5.010; use Data::Dumper::Names; my $orig = 'Apple iPhone 4 Black Cover'; my $want = 'Appl-iPho-4-Blac-Cove'; say Dumper $orig, $want; my $trim = join ' ', (split /\s+/, $orig)[0..1]; say Dumper $trim; say "THE PROBLEM WITH YOUR ATTEMPT IS RETURN VALUE OF SPLIT ", Dumper( +[ split /\s+/, $orig ]); say "OF WHICH YOU ONLY TAKE FIRST 2 ", Dumper([ (split /\s+/, $orig)[0 +..1] ]); say "YOU NEED MATCH OPERATOR AND MAP AS WELL"; $trim = join '-', map { /^(\w{1,4})/ } split /\s+/, $orig; say Dumper $want, $trim ; say "SAME THING USING SUBSTITUTION OPERATOR"; $trim = $orig; $trim =~ s{ (?: (\w{1,4}) # capture first 1-to-4 word chars in $1 \w* # match and ignore any remaining words ) | # or (\s+) # any save any-amount-of-whitespace into $2 }{ defined $2 # if defined $2 ? '-' # then return '-' : $1; # else return $1 }gex; say Dumper $want, $trim ; $trim = $orig; say "AND MAYBE FASTER, first transliterate spaces into -"; $trim =~ tr/\t\r\n /-/s; say Dumper $trim; say "then shorten words to 4 chars using perl 5.10 feature \\K"; $trim =~ s{\w{4}\K\w*}{}g; # ignore first 4 word chars, delete others say Dumper $want, $trim ; say "USING MATCH OPERATOR ONLY "; $trim = join '-', $orig =~ m{(\w{4})\w*\b|(\w{1,3})}g; say Dumper $want, $trim ; say "THOSE CAPTURE GROUPS ARE TRICKY "; $trim = join '-', grep defined, $orig =~ m{(\w{4})\w*\b|(\w{1,3})}g; say Dumper $want, $trim ; __END__ $ perl trim.pl $orig = 'Apple iPhone 4 Black Cover'; $want = 'Appl-iPho-4-Blac-Cove'; $trim = 'Apple iPhone'; THE PROBLEM WITH YOUR ATTEMPT IS RETURN VALUE OF SPLIT $VAR1 = [ 'Apple', 'iPhone', '4', 'Black', 'Cover' ]; OF WHICH YOU ONLY TAKE FIRST 2 $VAR1 = [ 'Apple', 'iPhone' ]; YOU NEED MATCH OPERATOR AND MAP AS WELL $want = 'Appl-iPho-4-Blac-Cove'; $trim = 'Appl-iPho-4-Blac-Cove'; SAME THING USING SUBSTITUTION OPERATOR $want = 'Appl-iPho-4-Blac-Cove'; $trim = 'Appl-iPho-4-Blac-Cove'; AND MAYBE FASTER, first transliterate spaces into - $trim = 'Apple-iPhone-4-Black-Cover'; then shorten words to 4 chars using perl 5.10 feature \K $want = 'Appl-iPho-4-Blac-Cove'; $trim = 'Appl-iPho-4-Blac-Cove'; USING MATCH OPERATOR ONLY Use of uninitialized value $orig in join or string at trim.pl line 42. Use of uninitialized value $orig in join or string at trim.pl line 42. Use of uninitialized value $orig in join or string at trim.pl line 42. Use of uninitialized value $orig in join or string at trim.pl line 42. Use of uninitialized value $orig in join or string at trim.pl line 42. $want = 'Appl-iPho-4-Blac-Cove'; $trim = 'Appl--iPho---4-Blac--Cove-'; THOSE CAPTURE GROUPS ARE TRICKY $want = 'Appl-iPho-4-Blac-Cove'; $trim = 'Appl-iPho-4-Blac-Cove';
        Thank you so much Anon Monk! that is perfect!!! and a great way to learn :) Thank you once again!

        Its even simpler than that , append

        say "BUT YOU CAN USE LESS OF THEM :) OR LEARN FROM s/// "; $trim = join '-', $orig =~ m{(\w{1,4})\w*}g; say Dumper $want, $trim ;

        and get extra output

        BUT YOU CAN USE LESS OF THEM :) OR LEARN FROM s/// $want = 'Appl-iPho-4-Blac-Cove'; $trim = 'Appl-iPho-4-Blac-Cove';

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