cycle package:base-prelude

cycle ties a finite list into a circular one, or equivalently, the infinite repetition of the original list. It is the identity on infinite lists.

>>> cycle []
*** Exception: Prelude.cycle: empty list

>>> take 20 $ cycle [42]
[42,42,42,42,42,42,42,42,42,42...

>>> take 20 $ cycle [2, 5, 7]
[2,5,7,2,5,7,2,5,7,2,5,7...

A generalization of cycle to an arbitrary Semigroup. May fail to terminate for some values in some semigroups.