如何找出运算符"+"的类型? [英] How can I find out the type of operator "+"?

问题描述

在GHCi版本8.6.3中( https://repl.it/languages/haskell )，我想知道如何找出运算符"+"的类型.我想看看它的类型是num a, b,c => a -> b -> c还是num a, b,c => (a,b) -> c.

In GHCi, version 8.6.3 (https://repl.it/languages/haskell), I would like to know how to find out the type of operator "+". I want to see if its type is num a, b,c => a -> b -> c or num a, b,c => (a,b) -> c.

但是我找不到它的类型.它还以未知方式影响下一个表达式.为什么我失败了，我该怎么办?

But I can't find its type out. It also affects the next expression in an unknown way. Why do I fail and what shall I do then?

   :type +
   :type not
<interactive>:1:1: error: parse error on input ‘+’
   :type not
not :: Bool -> Bool
=> "12"

推荐答案

这种方式:

> :type (+)
(+) :: Num a => a -> a -> a

还有

> :t (+) 4
(+) 4 :: Num a => a -> a

> :t (+) 4 3
(+) 4 3 :: Num a => a

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