Creating 2 D arrays dynamically in Perl

Question

I want to create 2-d arrays dynamically in Perl. I am not sure how to do this exactly.My requirement is something like this-

@a =([0,1,...],[1,0,1..],...)

Also I want to name the references to the internal array dynamically. i.e. I must be able to refer to my internal arrays with my chosen names which I will be allocating dynamically. Can someone please help me on this.

Possible duplicate of [Using a dynamically generated variable name in Perl's strict mode](http://stackoverflow.com/questions/17434333/using-a-dynamically-generated-variable-name-in-perls-strict-mode) — AbhiNickz, Jan 17 '17 at 09:30
Can you please explain a bit more what you mean by _name_ and what should be _dynamic_ about them? Maybe include an example, even if it has wrong syntax. Right now I think you don't want to do what Abhi believes, but I could be wrong. If it's what he suggests, then don't do it. It will cause you loads of grieve. But we'd need a better explanation to tell. — simbabque, Jan 17 '17 at 12:51

score 2 · Accepted Answer · edited Jan 17 '17 at 12:49

2

It sounds like you want a tree/hash of arrays. Use references to achieve this.

Example of hash of array of array:

$ref = {};
$ref->{'name'} = [];
$ref->{'name'}[0] = [];
$ref->{'name'}[0][1] = 3;

This could be dynamic if required. Make sure you initialise what the reference is pointing at.

edited Jan 17 '17 at 12:49

simbabque

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answered Jan 17 '17 at 09:52

Essex Boy

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In my practice, I prefer to use arrays of pointers, e.g. $ref->{'name'}->[0]->[1], as you will always pass these things as pointers to functions and will not copy the data contained within - it will save you a lot of memory and performance on huge arrays. – mickvav Jan 20 '17 at 14:40
@mickvav $ref->{'name'}->[0]->[1] is exactly the same as $ref->{'name'}[0][1] – Essex Boy Jan 20 '17 at 15:03

score 0 · Answer 2 · answered Jan 17 '17 at 09:58

0

Example array of array references:

my @x;
$x[$_] = [0..int(rand(5)+1)] for (0..3);

answered Jan 17 '17 at 09:58

palik

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score 0 · Answer 3 · answered Jan 17 '17 at 13:51

You probably have some kind of loop?

for (...) {
    my @subarray = ...;
    push @a, \@subarray;
}

You could also do

for (...) {
    push @a, [ ... ];
}

If it's actually a foreach loop, you could even replace it with a map.

my @a = map { ...; [ ... ] } ...;

Creating 2 D arrays dynamically in Perl

3 Answers3