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

Sequences

A sequence is an ordered series of values produced one after another. Raku builds sequences with the ... operator, which figures out the pattern from the values you give it and generates the rest up to an endpoint.

The simplest case counts from one value to another:

say 1 ... 5; # (1 2 3 4 5)

If you provide two starting values, Raku takes the step between them and continues with the same step. This is how you make an arithmetic sequence:

say 1, 3 ... 11; # (1 3 5 7 9 11)

Here the starting values 1, 3 set the step to two, so Raku counts up in twos and stops once it reaches 11.

The value produced by ... is of the Seq type:

say (1 ... 5).WHAT; # (Seq)

The following topics show other patterns the ... operator can recognise, and how a sequence can be lazy — even infinite.

Course navigation

← Solution: Count in a bag   |   Sequence patterns →