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Depth of AoAs

by CharlesClarkson (Curate)
on Jan 14, 2002 at 10:17 UTC ( #138529=snippet: print w/ replies, xml ) Need Help??


I have no clue why anyone might need this. I created it while answering a question about multidimensional arrays. It is my first successful recursive sub.

    sub depth {
        my $arr = shift;
        return 1 unless ref $$arr[0] eq 'ARRAY';
        return depth( $$arr[0] ) + 1;

Call it with a reference to your array of arrays structure

print depth( \@array );

Update: Changed the fourth line to indicate the correct sub.

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Re: Depth of AoAs
by rob_au (Abbot) on Jan 14, 2002 at 10:33 UTC
    There are two small problems with this code - The first is that you have called the subroutine depth yet reference it within the subroutine as dimensions. Has anyone ever told you that recursion is evil? :-)

    Also, if the subroutine is called with something other than an array reference, it still returns a count of 1.



    This code addresses the issues above and returns the correct reference depth of the array.

    sub depth { return 0 unless ref $_[0] eq 'ARRAY'; return depth( ${$_[0]}[0] ) + 1; }

    Or alternatively, without recursion ...

    sub depth { my $array = shift; my $count = 0; while (ref $array eq 'ARRAY') { $array = ${$array}[0]; ++$count; } return $count; }



    Okay ... So I was curious and went ahead and benchmarked these subroutines and was pleasantly surprised with the result.

    Benchmark: timing 100000 iterations of loop, recursion... loop: 6 wallclock secs ( 5.30 usr + 0.00 sys = 5.30 CPU) @ 18 +867.92/s (n=100000) recursion: 6 wallclock secs ( 5.87 usr + 0.00 sys = 5.87 CPU) @ 17 +035.78/s (n=100000)


Re: Depth of AoAs
by merlyn (Sage) on Jan 15, 2002 at 02:50 UTC

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