Can you grep and remove simultaneously?

sub grep_in_place(&\@) {
   my ($cb, $array) = @_;
   my $src = -1;
   my $dst = -1;
   while (++$src < @$array) {
      my $keep;
      $keep = $cb->() for $array->[$src];
      $array->[++$dst] = $array->[$src] if $keep;
   }
   $#$array = $dst;
}

grep_in_place { ... } @array;

[download]

Uses O(1) memory

This could be done faster using XS since the the elements could be moved instead of copied.

Update: Fixed the proto. Added disappeared if $keep.

In reply to Re: Fastest way to grep multiple time on some array by ikegami
in thread Fastest way to grep multiple time on some array by Anonymous Monk

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