用于转换的 Haskell 标准库函数

Question

Haskell 有 Data.List.permutations

permutations "abc" == ["abc","bac","cba","bca","cab","acb"]

是否有用于转换的标准库函数，或者您需要自己构建吗？

transformations "ab" == ["aa","ab","ba","bb"]

Ruby 的方式是:

 x.repeated_permutation(x.length)

Answer 1

您正在寻找replicateM在 Control.Monad模块:

replicateM 2 "ab"
-- ["aa","ab","ba","bb"]

Live demo

据我所知，它们是字母表中重复的排列['a', 'b']。