haskell - Haskell中一元运算符的前缀形式

Question

在 GHCi 中:

1. Prelude> (+3) 2
   5
2. Prelude> (*3) 2
   6
3. Prelude> (/3) 2
   0.6666666666666666
4. Prelude> (-3) 2
   No instance for (Num (t -> t1))
   arising from the literal 3' at <interactive>:1:2

Possible fix: add an instance declaration for (Num (t -> t1))

In the expression: 3

In the expression: (- 3) 2

In the definition ofit': it = (- 3) 2

如何更正最后一个以使其返回-1？

Answer 1

Haskell 的语法不允许你使用 -像那样。使用 subtract代替功能:

(subtract 3) 2