how do you use the index function on this example?


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how do you use the index function on this example?

by Anonymous Monk

on Sep 21, 2015 at 19:40 UTC ( #1142662=perlquestion: print w/replies, xml )

Need Help??

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,
I need to use the index function and I found this example:

 #!/usr/bin/perl
  use strict;
  use warnings;

  my $string = 'perlmeme.org';
  my $char = 'e';
  my $offset = 0;

  my $result = index($string, $char, $offset);

  while ($result != -1) {

    print "Found $char at $result\n";

    $offset = $result + 1;
    $result = index($string, $char, $offset);

  }
[download]

This is very straightforward, BUT, how could one find all occurences of a string that is now known exactly beforehand?
Consider the string:

$string = 'IIIIMMMMMMMOOOOOOOOOOMMMMMMMMMMMMMMMIIIIIIMMMMOOOO';
[download]

and say you would like to find all occurences (starting positions and lengths) of the M's substrings.
How do I need to proceed?

Comment on how do you use the index function on this example? Select or Download Code

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Re: how do you use the index function on this example? by Anonymous Monk on Sep 21, 2015 at 19:48 UTC
Ah, never mind, I found this solution: `while($string=~/(M+)/g) { ($start, $end) = ($-[0], $+[0]); print $start."\t".$end."\n"; }` [download] Thanks	[reply] [d/l]
Re^2: how do you use the index function on this example? by AnomalousMonk (Archbishop) on Sep 21, 2015 at 22:12 UTC
And you don't even need the capturing parentheses: `c:\@Work\Perl>perl -wMstrict -le "my $string = 'IIIIMMMMMMMOOOOOOOOOOMMMMMMMMMMMMMMMIIIIIIMMMMOOOO'; ;; while ($string =~ /M+/g) { my ($start, $end) = ($-[0], $+[0]); print qq{start $start, end $end}; } " start 4, end 11 start 21, end 36 start 42, end 46` [download] Note that `@+` holds the positions of the first character after matched sub-strings! Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]

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