haskell迭代列表推导

Question

我想在Haskell

中这样做

对于MyString = "ab"和n = 4，结果应为＆gt;

["aaaa","aaab","aaba","aabb","abaa","abab","abba","abbb","baaa","baab","baba","babb","bbaa","bbab","bbba","bbbb"]

Answer 1

replicateM 4 "ab"

给出你要求的东西。您可以从Control.Monad。

导入它

Answer 2

如果你想自己写，你可以做以下事情。

seq i xs | i > 0 = [x:ys | x <- xs, ys <- seq (i-1) xs]
         | otherwise = [[]]