如何正确使用|>操作员？ [英] how to correctly use |> operator?

问题描述

当我尝试在榆木中使用 |> 运算符时出现错误

i get an error when i try use the |> operator in elm

kl : List Float
kl =
    List.map toFloat (List.range 1 10)

kll : Float
kll =
    let
        half x =
            x / 2
    in
    List.sum (List.map half (List.map toFloat (List.range 1 10)))

下面的代码我使用 |> 并得到错误：

The code below i use the |> and get an error:

klpipe : List Float
klpipe =
    1 10 |> List.range |> toFloat |> List.map

推荐答案

|> ; 只能用于将左侧的单个参数应用于右侧的函数。以下是一些示例，可以让您直观地了解其工作原理：

|> can only be used to apply a single argument on the left side to a function on the right side. Here's a few examples to give you an intuition of how it works:

x |> f == f x
y |> f x == f x y
f x |> g == g (f x)

您可以使用<将多个参数应用于单个函数code> |> ，但是您必须一次以反转顺序执行一次，并使用括号违背其自然的关联性：

You can apply multiple arguments to a single function using |>, but you'll have to do it one at a time in revers order and use parentheses to go against its natural associativity:

10 |> (1 |> List.range) |> (toFloat |> List.map)

此处带括号的表达式都评估为适合函数。在管道的右侧。没有括号， 1 |> 10 |> List.range 等同于`List.range（10 1）。

Here the parenthesized expressions both evaluate to functions that "fit" on the right side of the pipe. Without parentheses, 1 |> 10 |> List.range would be equivalent to `List.range (10 1).

但是我不觉得这很可读，而是使用管道

I don't find this very readable however, and would instead use the pipe operator much more sparingly:

List.range 1 10 |> List.map toFloat

仅仅因为您可以使它看起来像钉子，并不意味着您应该在上面用锤子

Just because you can make it look like a nail doesn't mean you should use a hammer on it.

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