Question

the type of 1+ is given as :

Prelude> :t (1+)
(1+) :: Num a => a -> a

Is the correct way to read this function as :

1+ takes a Num and returns a function of type a -> a ?

Answer 1

1+ takes an a and returns an a with the restriction that a must be an instance of Num.

Answer 2

No, Num a is a class constraint, which is implied by the different arrow (=>).

+1 is a function from a to a where a must be an instance of the Num typeclass.

For more information see the part of Learn you a Haskell.

Answer 3

不，在Haskell中= =＆gt;之前的部分表示参数必须是其实例的类约束。所以，

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

这意味着（1+）是一个函数，它接受参数“a”并返回参数“a”，其中参数“a”必须是类约束Num的实例。