Haskell标准库函数用于转换

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滚动吗？

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

Ruby方式是:

 x.repeated_permutation(x.length)

Answer 1

您正在寻找replicateM的在Control.Monad模块:

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

Live demo

AFAIK它们是字母表中重复的排列['a', 'b'].