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

By inserting slips as appropriate, eg via

.combinations(2).map(*.permutations.Slip).Array

or

[ slip .permutations for .combinations(2) ]

Invoking .Array in the first example is unnecessary if you're fine with a Seq, and can be replaced with calls to .list or .cache (supplied by PositionalBindFailover) if mutability is not needed.

In the second example, the prefix | operator could be used instead of the slip sub.