在F#中，>>是什么?运算符是什么意思? [英] In F# what does the >> operator mean?

问题描述

我在此示例中的一些代码中注意到了包含>>运算符:

I noticed in some code in this sample that contained the >> operator:

let printTree =
  tree >> Seq.iter (Seq.fold (+) "" >> printfn "%s")

>>运算符是什么意思?

What does the >> operator mean/do?

非常感谢，现在更加清晰了. 这是我生成的示例，可以用来解决此问题:

Thanks very much, now it is much clearer. Here's my example I generated to get the hang of it:

open System
open System.IO

let read_lines path = File.ReadAllLines(path) |> Array.to_list

let trim line = (string line).Trim()
let to_upper line = (string line).ToUpper()

let new_list = [ for line in read_lines "myText.txt" -> line |> (trim >> to_upper) ]

printf "%A" new_list

推荐答案

它是函数组合运算符.

有关克里斯·史密斯博客文章的更多信息

介绍功能组成 运算符(>>):

Introducing the Function Composition operator (>>):

let inline (>>) f g x = g(f x)

读为:给定两个函数，f 和g，以及一个值x，计算出 x的f的结果并传递该结果 到g.有趣的是 您可以使用(>>)函数 并且只传递参数f和g， 结果是一个需要一个函数的函数 单个参数并产生 结果g(f(x)).

Which reads as: given two functions, f and g, and a value, x, compute the result of f of x and pass that result to g. The interesting thing here is that you can curry the (>>) function and only pass in parameters f and g, the result is a function which takes a single parameter and produces the result g ( f ( x ) ).

这是组成一个简单的例子 较小的功能:

Here's a quick example of composing a function out of smaller ones:

let negate x = x * -1 
let square x = x * x 
let print  x = printfn "The number is: %d" x
let square_negate_then_print = square >> negate >> print 
asserdo square_negate_then_print 2

执行时会打印"-4".

When executed prints ‘-4’.

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