haskell中的++和:有什么区别? [英] What is the difference between ++ and : in haskell?

问题描述

我不明白-

Prelude> "hi"++"there"
"hithere"
Prelude> "hi":"there"

<interactive>:12:6:
    Couldn't match expected type `[Char]' with actual type `Char'
    Expected type: [[Char]]
      Actual type: [Char]
    In the second argument of `(:)', namely `"there"'
    In the expression: "hi" : "there"
Prelude> 

为什么不还返回"hithere"?

Why doesn't that also return "hithere"?

推荐答案

类型.在GCHi中尝试以下方法:

The types. Try this in GCHi:

Prelude> :t (:)
(:) :: a -> [a] -> [a]
Prelude. :t (++)
(++) :: [a] -> [a] -> [a]

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