Re^2: Fastest way to grep multiple time on some array

It doesn't quite work. grep_and_remove() should do the trick:

use warnings;
use strict;

use Data::Dumper;

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];
   }
   $#$array = $dst;
}

sub grep_and_remove (&\@) {
   my ($cb, $array_ref) = @_;
   my @found;
   my $i = 0;

   GREP:
   while ($i < @{ $array_ref })
   {
       $cb->()
           and push(@found, splice(@{ $array_ref }, $i, 1))
           and next GREP
             for $array_ref->[$i];
       ++$i;
   }

   return @found;
}

my @arr1 = (1,2,3,4,5,6,7,8);
my @arr2 = grep_in_place   { $_ > 4 } @arr1;

my @arr3 = (1,2,3,4,5,6,7,8);
my @arr4 = grep_and_remove { $_ > 4 } @arr3;

print Dumper(\@arr1, \@arr2, \@arr3, \@arr4);

__END__
$VAR1 = [
          1,
          2,
          3,
          4,
          5,
          6,
          7,
          8
        ];
$VAR2 = [
          '-1'
        ];
$VAR3 = [
          1,
          2,
          3,
          4
        ];
$VAR4 = [
          5,
          6,
          7,
          8
        ];
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Re^3: Fastest way to grep multiple time on some array by ikegami (Patriarch) on Feb 19, 2009 at 23:57 UTC
You used it wrong, but I see I used the wrong prototype, and my "if $keep" disappeared. `use strict; use warnings; sub grep_in_place(&\@) { my ($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; } my @a = (1,2,3,4,5,6,7,8); print("Before: @a\n"); grep_in_place { $_ > 4 } @a; print("After: @a\n");` [download] `Before: 1 2 3 4 5 6 7 8 After: 5 6 7 8` [download] To get your (and probably the OP's) semantics: `sub grep_and_remove(&\@) { my ($cb, $array) = @_; my $src = -1; my $dst = -1; my @deleted; while (++$src < @$array) { my $keep; $keep = $cb->() for $array->[$src]; ($keep ? $deleted[@deleted] : $array->[++$dst] ) = $array->[$src]; } $#$array = $dst; return @deleted; } my @a = (1,2,3,4,5,6,7,8); print("Before: @a\n"); my @b = grep_and_remove { $_ > 4 } @a; print("After: @a\n"); print("Returned: @b\n");` [download] `Before: 1 2 3 4 5 6 7 8 After: 1 2 3 4 Returned: 5 6 7 8` [download] No crazy splice!	[reply] [d/l] [select]
Re^4: Fastest way to grep multiple time on some array by repellent (Priest) on Feb 20, 2009 at 02:16 UTC
Thanks for the clarification and the better way! :)	[reply]