将元组输入到诸如printfn之类的函数中 [英] Feeding tuple into function such as printfn

问题描述

我想给一个元组一个printf函数:

I want to give a tuple to a printf function:

let tuple = ("Hello", "world")
do printfn "%s %s" tuple

这当然是行不通的，编译器首先说，它需要string而不是string*string.我将其编写如下:

This, of course, does not work, compiler first says, that it needs string instead of string*string. I write it as follows:

let tuple = ("Hello", "world")
do printfn "%s %s" <| fst tuple

然后编译器合理地指出，现在我具有类型为string -> unit的函数值.说得通.我会写

Then compiler reasonably notes that now I have function value of type string -> unit. Makes sense. I can write

let tuple = ("Hello", "world")
do printfn "%s %s" <| fst tuple <| snd tuple

它对我有用.但我想知道，是否有什么办法可以做到更好，例如

And it works for me. But I'm wondering, if there might be any way to do it nicer, like

let tuple = ("Hello", "world")
do printfn "%s %s" <| magic tuple

我的问题是我无法获得printf需要哪种类型来打印两个参数. magic函数是什么样的?

My problem is that I can't get which type does printf need so that to print two arguments. What could magic function look like?

推荐答案

您要

let tuple = ("Hello", "world")   
printfn "%s %s" <|| tuple

请注意<||中的双||，而不是<|

Notice the double || in <|| and not a single | in <|

请参阅: MSDN <||

您也可以

let tuple = ("Hello", "world")
tuple
||> printfn "%s %s"

还有其他类似的运算符，例如|>，||>，|||>，<|，<||和<|||.

There are other similar operators such as |>, ||>, |||>, <|, <||, and <|||.

使用fst和snd的惯用方式是

let tuple = ("Hello", "world")
printfn "%s %s" (fst tuple) (snd tuple)

通常看不到使用||>或< ||传递给函数的元组的原因运营商的原因是解构.

The reason you don't usually see a tuple passed to a function with one of the ||> or <|| operators is because of what is known as a destructuring.

破坏性表达式采用复合类型并将其分解为多个部分.

A destructing expression takes a compound type and destructs it into parts.

因此对于tuple ("Hello", "world")，我们可以创建一个析构函数，将元组分为两部分.

So for the tuple ("Hello", "world") we can create a destructor which breaks the tuple into two parts.

let (a,b) = tuple

我知道对于F#刚接触的人来说，这看起来像一个元组构造函数，或者看起来更奇怪，因为我们绑定了两个值(注意，我说是绑定且未分配)，但是它使用具有两个值的元组并将其分解为两个单独的值.

I know this may look like a tuple constructor to someone new to F#, or may look even odder because we have two values being bound to, (noticed I said bound and not assigned), but it takes the tuple with two values and destructured it into two separate values.

所以在这里，我们使用解构表达式来实现它.

So here we do it using a destructuring expression.

let tuple = ("Hello", "world")
let (a,b) = tuple
printfn "%s %s" a b

或更常见的

let (a,b) = ("Hello", "world")
printfn "%s %s" a b

这篇关于将元组输入到诸如printfn之类的函数中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！