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Re: Scoped Variables in a Recursive Function.

by japhy (Canon)
on Sep 28, 2000 at 16:46 UTC ( #34369=note: print w/replies, xml ) Need Help??

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... } }


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RE: Re: Scoped Variables in a Recursive Function.
by Adam (Vicar) on Sep 28, 2000 at 19:46 UTC
    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; }
      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.

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

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