haskell -++ 和 : in haskell? 有什么区别

Question

我不明白这个——

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> 

为什么那不也返回“到那里”？

Answer 1

类型。在 GCHi 中试试这个:

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