如何阅读F#类型签名? [英] How to read F# type signatures?
问题描述
我正在为F#类型签名表示法而苦苦挣扎.例如，假设您具有Fold函数:
I'm struggling with the F# type signature notation. For example let's say you have a Fold function:
let rec Fold combine acc l =
...
可能具有以下类型签名:
that may have this type signature:
('a -> 'b -> 'a) -> 'a -> list<'b> -> 'a
我会读为
具有三个参数的函数:
- 接受'a，'b并返回a'的函数
- 一个'a
- "b 的列表
- a function that takes an 'a, a 'b and returns an a'
- an 'a
- a list of 'b
并返回一个'a.
但是，对于我的穴居人的大脑来说，将其表达为
But then it would make more sense for my cavemen brain to express it as
('a, 'b -> 'a), 'a, list<'b> -> 'a
我肯定有一个语义上的原因，为什么用箭头分隔参数的方式与函数返回类型的方式完全相同，但是以某种方式我却错过了它，并且到目前为止在书/文章中都没有找到明确的解释.每次我看到类型签名时，我都必须花很多时间来理解它.我觉得我只是缺少使解密"变得显而易见的那一小部分拼图.
I'm sure there is a semantic reason why parameters are separated with an arrow exactly the same way as the function return type, but somehow I'm missing it and didn't found a clear explanation in books/articles so far. Every time I see a type signature I have to stop quite a bit of time to understand it. I feel like I'm just missing that little piece of the puzzle that makes the "decryption" obvious.
有人可以启发我吗?
推荐答案
我确定这是语义上的原因 为什么参数用 箭头与 函数返回类型，但是我不知何故 错过了，没有找到一个明确的 到目前为止，在书籍/文章中都有解释.
I'm sure there is a semantic reason why parameters are separated with an arrow exactly the same way as the function return type, but somehow I'm missing it and didn't found a clear explanation in books/articles so far.
您正在阅读的第一个功能是正确的.对于即时解密，类型签名表示为:
You're reading of the first function is correct. For instant deciphering, type signatures are expressed like this:
val functionName = inputType1 -> inputType2 -> ... -> inputTypeN -> returnType
通常，箭头表示功能是可咖喱的.
Generally, arrow notation indicates a function is curry-able.
// val add4 : int -> int -> int -> int -> int
let add4 a b c d = a + b + c + d;;
// val f : (int -> int)
let f = add4 1 2 3 // returns (int -> int) waiting for last argument
由于该函数是经过咖喱处理的，因此您可以在技术上这样写:
Because the function is curried, you can technically write it like this:
// val add4 : int -> int -> int -> int -> int
let add4 = (fun a -> (fun b -> (fun c -> (fun d -> a + b + c + d))));;
// val f : (int -> int)
let f = fun x -> add4 1 2 3 x
考虑一下，add4签名与此等效:
If you think about it, the add4 signature is equivalent to this:
val add4 : int -> (int -> (int -> (int -> int) ) )
我相信我们使用箭头表示法是因为当我们显式咖喱参数时，它类似于函数的结构.
I believe we use arrow notation because it resembles the structure of the function when we explicitly curry arguments as shown above.
这篇关于如何阅读F#类型签名?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
