为什么(.)称为中缀.而不是`(.)`

我了解到可以通过两种方式调用函数:前缀和中缀.例如，假设我创建了此函数:

I learned that functions can be invoked in two ways; prefix and infix. For example, say I've created this function:

example :: [Char] -> [Char] -> [Char]
example x y = x ++ " " ++ y

我可以这样称呼它为前缀:

I can call it prefix like so:

example "Hello" "World"

或像这样的中缀:

"Hello" `example` "World"

这两个都将导致表示字符串"Hello World" 的字符列表.

Both of which will result in the list of chars representing a string "Hello World".

但是，我现在正在学习有关函数组成的知识，并且遇到了如下定义的函数:

However, I am now learning about function composition, and have come across the function defined like so:

(.) :: (b -> c) -> (a -> b) -> a -> c

所以，说我想乘以3来求和.我会像这样写前缀调用:

So, say I was wanting to compose negate with multiplication by three. I would write the prefix invocation like:

negateComposedWithMultByThree = (.) negate (*3) 

和infix调用类似:

And the infix invocation like:

negateComposedWithMultByThree = negate `(.)` (*3)

但是，虽然前缀调用可以编译，但infix调用却不会，而是显示错误消息:

But, whilst the prefix invocation compiles, the infix invocation does not and instead gives me the error message:

错误:解析输入`('

error: parse error on input `('

看来，要调用撰写中缀，我需要省略方括号并这样称呼它:

It seems, in order to call compose infix, I need to omit the brackets and call it like so:

negateComposedWithMultByThree = negate . (*3)

任何人都可以阐明这一点吗?为什么"Hello"`example`"World" 而否定`(.)`(* 3)却为什么呢?

Can anyone shed any light on this? Why does "Hello" `example` "World" whilst negate `(.)` (*3) does not?

此外，如果我尝试使用这样的签名来实现自己的功能:

In addition, if I try to make my own function with a signature like this:

(,) :: Int -> Int
(,) x = 1

它无法编译，并显示错误:

It does not compile, with the error:

无效的类型签名(，):...的形式应为::"

"Invalid type signature (,) : ... Should be of form :: "