Beefy Boxes and Bandwidth Generously Provided by pair Networks
Clear questions and runnable code
get the best and fastest answer

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.

Replies are listed 'Best First'.
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
Log In?

What's my password?
Create A New User
Node Status?
node history
Node Type: snippet [id://138529]
and all is quiet...

How do I use this? | Other CB clients
Other Users?
Others surveying the Monastery: (7)
As of 2017-11-17 23:33 GMT
Find Nodes?
    Voting Booth?
    In order to be able to say "I know Perl", you must have:

    Results (276 votes). Check out past polls.