Course of Raku / Advanced / More about built-in types

Sets, bags, and mixes

Besides arrays and hashes, Raku offers a few specialised containers for collections of values. The simplest is the Set — an unordered collection of distinct values, where each value is either a member or not, and duplicates are ignored.

You create a set with the set routine. Repeated values collapse into one:

my $s = set(1, 2, 3, 2, 1);
say $s.elems; # 3

Even though five numbers were passed in, the set has only three elements, because 1 and 2 appeared more than once.

The main question you ask a set is whether a value belongs to it. The ∈ operator (read as “is an element of”) returns a Boolean:

say 2 ∈ set(1, 2, 3); # True
say 9 ∈ set(1, 2, 3); # False

If you prefer to stay with plain ASCII, the same operator can be written as (elem):

say 2 (elem) set(1, 2, 3); # True

The following topics show how to combine sets, and introduce bags and mixes, which are close relatives of the set.

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