通过函数调用进行模式匹配 [英] Pattern matching by function call

问题描述

F#通过模式匹配分配函数参数.这就是为什么

F# assigns function arguments via pattern matching. This is why

// ok: pattern matching of tuples upon function call
let g (a,b) = a + b
g (7,4)

有效:元组与(a，b)匹配，并且a和b直接在f内部可用.

works: The tuple is matched with (a,b) and a and b are available directly inside f.

对有歧视的工会做同样的事情同样会有所裨益，但我无法做到这一点:

Doing the same with discriminated unions would be equally beneficial, but I cannot get it to done:

// error: same with discriminated unions
type A = 
    | X of int * int
    | Y of string

let f A.X(a, b) = a + b // Error: Successive patterns 
                        // should be separated by spaces or tupled

// EDIT, integrating the answer:
let f (A.X(a, b)) = a + b // correct

f (A.X(7, 4))

作为函数调用的一部分的模式匹配是否仅限于元组?有办法解决歧视工会吗?

Is pattern matching as part of the function call limited to tuples? Is there a way to do it with discriminated unions?

推荐答案

您需要额外的括号:

let f (A.X(a, b)) = a + b

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