Question

I have a data file like a two-dimensional array

22950   12
80044   22
02942   06
42018   20
63829   10
...

I want to shuffle this array into a random order, like

42018   20
22950   12
...

Looks like the ‘shuffle’ in List can be used to shuffle a vector, how to keep handle this kind of two-dimensional array?

Answer 1

Since you are only shuffling the first dimension of the array, List::Util::shuffle will work without any modification.

Perl does not have multi-dimentional arrays, it has arrays of scalars, each of which can also be an array. This is effectively a multi-dimentional array, but it means that you can use normal array operations like shuffle, since shuffle does not care what the values of the array are (and in this case they will be other arrays).

so the line:

my @random = shuffle \@array1, \@array2, \@array3;

is the same as

my @random = shuffle 1, 2, 3;

as far as shuffle is concerned (a list of 3 elements to shuffle).

so assuming your 2D data is contained in the array @data

my @data = (
    [1234, 34],
    [4564, 45],
    ...
);

then you would just write:

use List::Util 'shuffle';
my @random = shuffle @data;

and then you would access the 2D structure normally:

say $random[0][1];