F#，前移第一个参数 [英] F#, Pipe-forward first argument

问题描述

与此问题非常相似: F#管道优先参数

Quite similar to this question: F# pipe first parameter

我目前正在学习F#和函数编程，我想知道是否存在一种简便的方法来传递第一个参数(而不是最后一个参数).

I am currently learning F# and functional programming, and I want to know if there is an easy way to pipe-forward a first argument (instead of last argument).

例如，如果我想传递最后一个参数，它看起来非常干净:

For example, if I want to pipe forward the last argument, it looks very nice and clean:

[4;5;6]
    |> List.append [1;2;3]

// Result: [1;2;3;4;5;6]

如果我想传递第一个参数，可以使用"fun x->"函数，但是我只是想知道是否有更干净的方法.

If I want to pipe-forward the first argument, I can use a "fun x ->" function, but I am just curious if there is a cleaner way.

[1;2;3]
    |> fun x -> List.append x [4;5;6]

// Result: [1;2;3;4;5;6] 

非常感谢您.

P.S.我的同事只是帮助我解决了这个问题.但是，如果您对F#初学者有任何建议，我将不胜感激.谢谢.

P.S. My coworker just helped me with this problem. But I would appreciate any help if you have any suggestions for an F# beginner. Thank you.

推荐答案

当参数的顺序不方便时，您始终可以转换函数本身，使其以不同的顺序接受参数:

When the order of arguments is inconvenient, you can always transform the function itself to make it take the arguments in a different order:

let flip f x y = f y x

[1; 2; 3]
    |> (flip List.append) [4; 5; 6]

转换功能在许多情况下都很有用.这是功能性程序员的食粮.

Transforming functions is useful in many contexts. It is a functional programmer's bread and butter.

但是最后，我相信可读性是最重要的:程序的读取比编写的频率要高得多.当我发现自己处于类似情况下，并且由于某种原因不想命名中间值或使用lambda表达式时，我为自己定义了一个直观易懂的函数:

But in the end, I believe, readability is most important: programs are read incomparably more often than they are written. When I find myself in a similar situation, and I don't want to name the intermediate value or use a lambda expression for some reason, I define myself a function that would be intuitive to understand:

let prependTo a b = List.append b a

[1; 2; 3] 
   |> prependTo [4; 5; 6]

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