Re: Scoped Variables in a Recursive Function.

[japhy]

in reply to Scoped Variables in a Recursive Function.

You should not define a function inside a function. It does not behave as you'd expect. Instead, change your scoping slightly:

{
  my @array;
  sub Merge {
    @array = @_;
    MergeSort(0, $#array);
  }
  sub MergeSort {
    # can see @array here...
  }
}

$_="goto+F.print+chop;\n=yhpaj";F1:eval

[Adam]

That will work, but as tilly pointed out, the problem is with the MergeSort code being named. This aught to work with the fewest changes to your code:

sub Merge(@) {
  my @array = @_;

  local $MergeSort = sub { ### Anonymous code ref. ###
    my $first = shift;
    my $last = shift;
    if ($last>$first) {
      my $mid = int(($last+$first)/2);
      $MergeSort->($first, $mid);
      $MergeSort->($mid+1, $last);
      my @b;
      
      @b = ( @array[$first..$mid], @array[reverse($mid+1..$last)] );
      my ($i, $j, $k) = (0, $last-$first, $first);
      for (; $k<=$last; $k++) {
        $array[$k] = ($b[$i]<$b[$j]) ? $b[$i++] : $b[$j--];
      }
    }
  }

  $MergeSort->(0, $#array);
  return @array;

}

[japhy]

That ought to work, but it's silly, since it creates a code reference EVERY TIME you run Merge(). There's no reason to use a code reference. Define Merge() and MergeSort() in the same block, and have @array be shared between them.

$_="goto+F.print+chop;\n=yhpaj";F1:eval

[Adam]

Yeah, I was thinking about that... I think you are right.