Haskell从String中删除Chars [英] Haskell delete Chars from String

问题描述

我想写一个形式的函数

f :: String -> [String]
f str = ...

返回所有形成的字符串通过从 str 中删除​​一个字符。例如：

that returns the list of all the strings formed by removing exactly one character from str. For example:

ghci> f "stack"
["tack","sack","stck","stak","stac"]

$ b b

因为 String 和 [Char] 是同义词，我可以使用索引，我知道你应该避免在Haskell这样做。除了使用索引，还有更好的方法吗？

Because String and [Char] are synonymous, I could use the index, but I know that you should avoid doing that in Haskell. Is there a better way besides using the index?

推荐答案

你可以使用递归：

f :: [a] -> [[a]]
f [] = []
f (s:ss) = ss : map (s:) (f ss)

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