IteratorArgumentsResults
product()p, q, … [repeat=1]cartesian product, equivalent to a nested for-loop
permutations()p[, r]r-length tuples, all possible orderings, no repeated elements
combinations()p, rr-length tuples, in sorted order, no repeated elements
combinations_with_replacement()p, rr-length tuples, in sorted order, with repeated elements

(echo:: @ )