How to "convert" array into list?

Question

I need to use function cartesian from List::Gen. This function requires LIST as a second parameter, but I have an array, like

$VAR1 = [
 [
 1,
 2,
 3
 ],
 [
 'a',
 'b',
 'c'
 ],
 [
 'x'
 ]
 ];

How can I "convert" such array into list, so cartesian can be used? Putting array into list context does not seems to work in this case.

• TLP: An array is a list, if you put it in list context.
• TLP: The only time you need to differentiate between LIST and ARRAY is when you are using a function which handles arrays in a specific manner, such as push. Then the argument needs to be an array. There is no reversed incompatibility: A LIST can always be an array, but ARRAY cannot always be a list.
• ysth: to summarize the comments so far: the example array you give shows a misunderstanding of perl syntax regarding parentheses vs. brackets. So we don't know what your actual array looks like. Show us, using your actual data and the output of use Data::Dumper; print Dumper \@a;
• Ωmega: I am sorry for unclear question and example. I end up with the following solution: my @b = Set::CrossProduct->new([@a])->combinations;
• ikegami: If you want to ask a new a question, create a new post instead of replacing the old one!

Answer 1

Parens don't create lists, they just change precedence.

@a = ((1, 2, 3), (7, 8, 9));

is the same as

@a = (1, 2, 3, 7, 8, 9);

The examples of cartesian show a list of references to arrays

cartesian { $_[0] . $_[1] } [1,2,3], [7,8,9];

So it seems you want to create an array containing two elements, each a reference to another array.

@a = ( [1,2,3], [7,8,9] );

Then, to answer your question, evaluating @a in list context will return these two references.

cartesian { $_[0] . $_[1] } @a;

• ikegami: So is your new question "How to convert an array of 6 elements into two reference to arrays of 3 elements?"? Not enough info. Not the right place to ask.
• TLP: @Ωmega @a = ((1, 2, 3), (7, 8, 9)) is not an array of arrays. It's just an array. use Data::Dumper; print Dumper \@a; to see for yourself.
• Borodin: Please use Data::Dump or an equivalent to dump the contents of the array you want to pass to cartesian. If you publish the results here then we will be able to help you better.

Answer 2

In your new question, you have

$VAR1 = [
 [
 1,
 2,
 3
 ],
 [
 'a',
 'b',
 'c'
 ],
 [
 'x'
 ]
 ];

Despite your claims that it doesn't work, all you need is to evaluate the array in list context.

cartesian { ... } @$VAR1;

For example,

( cartesian { join '|', @_ } @$VAR1 )->say;

gives

1|a|x 1|b|x 1|c|x 2|a|x 2|b|x 2|c|x 3|a|x 3|b|x 3|c|x