cycle package:Cabal-syntax

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

>>> cycle [42]
[42,42,42,42,42,42,42,42,42,42...

>>> cycle [2, 5, 7]
[2,5,7,2,5,7,2,5,7,2,5,7...
Ω(V + E). Compute the cycles of a graph. Requires amortized construction of graph.