How do I “flatten” a list of lists in perl 6?

Question

Let\'s say I want all permutations of 2 letters out of a, b and c.

I can do:

my @perm = .combinations(2)».permutations;
say @perm;
# [((         


        

Answer 1

Ultimately, you are building your list the wrong way to begin with. You can slip your permutations into the outer list like this.

.combinations(2).map(|*.permutations);

Which yields the following list

((a b) (b a) (a c) (c a) (b c) (c b)) 

According to the Bench module, this is about 300% faster than doing

.combinations(2).map(*.permutations)[*;*]