Haskell中的运算符和函数有什么区别? [英] What is the difference between an operator and a function in Haskell?

问题描述

我是Haskell的新手，而Infix和Prefix表示法的混合使用使我感到困惑. "+"这样的运算符和head这样的函数有什么区别?如何写一个1 c 1 = 2的运算符'c'?

I am new to Haskell and this mixture of Infix and Prefix notation is confusing me. What is the difference between an operator like '+' and a function like head? How do I write an operator 'c' which does this 1 c 1 = 2?

我发现这个定义是！ b =正确. Haskell怎么知道我正在定义！而不是功能吗?

I found this definition a ! b = True. How does Haskell know that I am defining ! and not a function a?

推荐答案

在Haskell中，要创建运算符，必​​须使用以下运算符":

In Haskell, to create an operator you must use the following "operator symbols":

！ #$％* +. /< =>? \ ^ | :-〜

! # $ % * + . / < = > ? \ ^ | : - ~

例如，

($$$) a b = a+b

定义一个运算符$$$，该运算符可以在表达式1 $$$ 1中使用，以产生值2.

Defines an operator $$$ which can be used in the expression 1 $$$ 1 to yield a value of 2.

从概念上讲，运算符和函数没有什么区别，您可以使用反引号或括号来使一个像另一个一样工作.

Conceptually, there is no difference between an operator and a function, and you can use backticks or parens to make one work like the other.

就这样100％清楚了，让我演示将函数转换为运算符，反之亦然:

Just so it is 100% clear, let me demonstrate turning a function into an operator and vice versa:

对于运算符'+'，以下两个表达式是等效的:

For the operator '+', the following two expressions are equivalent:

1+1
(+) 1 1

类似地，对于一个函数，以下两个表达式是等效的:

Similarly, for a function, the following two expressions are equivalent:

foo 1 2
1 `foo` 2

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