Ranges and sequences

Ranges count for you; the ... operator deduces whole sequences — even infinite ones.

You've met ranges in loops; they're values in their own right, and they work on letters too:

say (1..10).sum;
say ('a'..'e').list;
say (^5).list;

55
(a b c d e)
(0 1 2 3 4)

The sequence operator #

... builds a sequence from examples. Give it enough terms to spot the pattern and an end point:

say 1, 3, 5 ... 15;
say 1, 2, 4 ... 1024;

(1 3 5 7 9 11 13 15)
(1 2 4 8 16 32 64 128 256 512 1024)

Arithmetic from two terms, geometric from three. For anything fancier, give it the rule yourself — * + * means "add the previous two":

say (1, 1, * + * ... *).head(10);

(1 1 2 3 5 8 13 21 34 55)

That ... * means the sequence never ends — it's lazy, computed only as far as you ask. .head(10) asks for the first ten Fibonacci numbers, so that's all that gets computed.

Try it #

Print the first 8 powers of 3 — starting from 1 — using the sequence operator and .head.

say (...).head(8);

say (1, 3, 9 ... *).head(8);

(1 3 9 27 81 243 729 2187)