Re: regexp and substitute operator problem

There's a problem in the loop that removes items according to a regex. Whenever an item is removed, the items to the right are shifted over, but $i is still incremented. See:

  my @arr = qw/ foo foozle bar bar2 foo bar foo /;

  for (my $i=0; $i<@arr; $i++) {
    splice(@arr, $i, 1) if ($arr[$i] =~ /bar/);
  }
  print "$_\n" for (@arr);

  ## output: bar2 is NOT removed
[download]

It will fail to check the next item after each match. It's much simpler (and correct-er) to write:

  @chroms = grep { ! /[pqxy]/i } @chroms;
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Although, if you're dealing with a huge amount of genetic data, this will be very slow. A quick fix to the existing loop would be the slight change:

  for (my $i=0; $i<@chroms; $i++) {
    splice(@chroms, $i--, 1) if not $chroms[$i] =~ /[pqxy]/i;
  }                 ####
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This still may not be optimal, but it's in-place so should be faster than the grep.

About your second question... Off the top of my head, I'm not sure what's up with your regex... It's late for me!

blokhead

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Re: Re: regexp and substitute operator problem by dannoura (Pilgrim) on Jul 08, 2003 at 06:28 UTC
Yep, you're right, that was a pretty stupid mistake. Thanks for your help. This: `@chroms = grep { /[pqxy]/i } @chroms;` solves it.	[reply] [d/l]
Re: Re: Re: regexp and substitute operator problem by Dog and Pony (Priest) on Jul 08, 2003 at 06:37 UTC
As for your second question, just copy/pasting your code and the example text does output the hyphens and dots here. What are you displaying it on? Also, you might at least want to put some () around the central part of your regex, as in: `/\s($c*?)\s/` so you won't capture the whitespace around the matches as you do now. Or maybe that is what you wanted. You have moved into a dark place. It is pitch black. You are likely to be eaten by a grue.	[reply] [d/l]


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