Question

I want to do permutation in Perl. For example I have three arrays: ["big", "tiny", "small"] and then I have ["red", "yellow", "green"] and also ["apple", "pear", "banana"].

How do I get:

["big", "red", "apple"]
["big", "red", "pear"]

..etc..

["small", "green", "banana"]

I understand this is called permutation. But I am not sure how to do it. Also I don’t know how many arrays I can have. There may be three or four, so I don’t want to do nested loop.

Answer 1

That’s actually not permutation but Cartesian product. See Math::Cartesian::Product.

#!/usr/bin/perl

use strict; use warnings;

use Math::Cartesian::Product;

cartesian { print "@_\n" }
    ["big", "tiny", "small"],
    ["red", "yellow", "green"],
    ["apple", "pear", "banana"];

Output:

C:\Temp> uu
big red apple
big red pear
big red banana
big yellow apple
big yellow pear
big yellow banana
big green apple
big green pear
big green banana
tiny red apple
tiny red pear
tiny red banana
tiny yellow apple
tiny yellow pear
tiny yellow banana
tiny green apple
tiny green pear
tiny green banana
small red apple
small red pear
small red banana
small yellow apple
small yellow pear
small yellow banana
small green apple
small green pear
small green banana