F#与->匹配 [英] F# match with ->

问题描述

我想做类似的事情(Nemerle语法)

I want to make something like it (Nemerle syntax)

def something =
match(STT)
    | 1 with st= "Summ"
    | 2 with st= "AVG" =>
        $"$st : $(summbycol(counter,STT))"

在F#上，F#是真的吗?

on F# so is it real with F#?

推荐答案

如果我对您的理解正确，那么您希望将某些值分配给变量作为模式的一部分. F#中对此没有直接支持，但是您可以定义一个执行此操作的参数化活动模式:

If I understand you correctly, you'd like to assign some value to a variable as part of the pattern. There is no direct support for this in F#, but you can define a parameterized active pattern that does that:

let (|Let|) v e = (v, e)

match stt with 
| Let "Summ" (st, 1) 
| Let "AVG" (st, 2) -> srintf "%s ..." st

Let之后的字符串是模式的参数(并作为v的值传递).然后，该模式将返回一个包含绑定值和原始值的元组(以便您可以在元组的第二个参数中匹配原始值.

The string after Let is a parameter of the pattern (and is passed in as value of v). The pattern then returns a tuple containing the bound value and the original value (so you can match the original value in the second parameter of the tuple.

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