+1和-1之间的差异

问题描述

  
这是因为（ -  1）被解释为负数，但是（+ 1）被解释为curried函数（\ x-> 1 + x）。
 
 
在haskell中， （a **）是（**）a 和的语法糖（* * a）是（\ x  - > x ** a）。然而，（ - ）是一种特殊情况，因为它既是一元运算符（否定）又是二元运算符（减号）。因此，这种语法糖在这里不能被明确地应用。当你想（\ x  - > a-x）时，你可以写（ - ）a 正如已经在中回答的那样，您可以使用函数 negate 和减去以区分一元和二元  -  函数。
 
> :t (+1)
(+1) :: Num a => a -> a

> :t (-1)
(-1) :: Num a => a
How come the second one is not a function? Do I have to write (+(-1)) or is there a better way?
 解决方案 
This is because (-1) is interpreted as negative one, however (+1) is interpreted as the curried function (\x->1+x).
In haskell, (a **) is syntactic sugar for (**) a, and (** a) is (\x -> x ** a). However (-) is a special case since it is both a unary operator (negate) and a binary operator (minus). Therefore this syntactic sugar cannot be applied unambiguously here. When you want (\x -> a - x) you can write (-) a, and, as already answered in Currying subtraction, you can use the functions negate and subtract to disambiguate between the unary and binary -  functions.
                        
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