Re: Scoped Variables in a Recursive Function.

[extremely]

This is the sort of code where you wish pass-by-reference was more obvious to the beginning coder.

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

As others have stated nesting subroutines Doesn't Do What You Expect. =) The enclosure method is nice but you should get used to passing references where you can. In this case Merge makes a copy of the data and then passes a reference on to MergeSort to do with as it pleases. Each recursive level of MergeSort passes the reference down to the next level. Neat and simple.

HTH

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