check if 2 dimensional array is completely empty perl

Question

My understanding is that I can use

if (@array) { print "array not null"; }

to test if all the elements of an array are null. Is there a way I can use this to test a 2 dimensional array?

if (@array) test if array is empty/has no elements. If it has elements and these are undef/null, it will be boolean true. — mpapec
– mpapec, Commented May 8, 2014 at 15:19

tobyink · Accepted Answer · 2014-05-08 14:53:48Z

4

Essentially you need to loop through the first dimension of the array to find out if any of the sub-arrays contain anything. This works:

use List::Util qw( any );

if (any { @$_ } @array) { print "array not null\n"; }

If you're stuck using an old version of List::Util that doesn't provide any, in this case first will work as a reasonable substitute:

use List::Util qw( first );

if (first { @$_ } @array) { print "array not null\n"; }

Though I think than any better clarifies the intent of the code.

answered May 8, 2014 at 14:53

tobyink

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8 Comments

Why not just use map @$_, @array?

@Zaid any and first are short circuited. Map will loop even if first element is not empty

@DVK : (rolls eyes) :)

@Zaid - if your list has 100000000 elements, it's not such a trivial optimization

@DVK : Totally agree. To each his/her own problem domain.

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