F＃在字符串数组上使用List.map [英] F# Using List.map on an array of strings

问题描述

我试图使用F＃的List.map函数来调用我写入数组中每个字符串的函数。这里是我写的函数

pre $ $ $ $ $ $ b让filterWord wordToFilter =
Regex.Replace（wordToFilter，[^ a-zA-Z0-9 /！\'?.-]，）;

以下是我称之为的主要方法

 （*程序的主要方法*）
 [< EntryPoint>] 
 let main argsv = 
 let input = File.ReadAllText （Alice in Wonderland.txt）; //将所有文本读入单个字符串
 let unfilteredWords = input.Split（''）; 
 let filteredWords = unfilteredWords |> List.map（fun x  - > filterWord（x））; 
 0; 
  

问题是我的List.map调用中出现语法错误，说

 错误类型不匹配。期待
字符串[]  - > 'a 
但给出
'b列表 - > 'c list 
'string []'类型与列表'
  

不匹配将input.split更改为硬编码的字符串数组修复了错误，因此它与F＃没有实现输入的结果有关.split可以与map函数一起使用，因为它是一个字符串数组。我只是不知道如何改变代码，因此它完成了我想完成的任务。我相对较新的F＃，所以我可以得到任何帮助将不胜感激！

解决方案

F＃没有实现input.split的结果，可以与map函数一起使用，因为它是一个字符串数组

List.map 可用于 list s，所以F＃意识到结果不能与<$ c $一起使用C> List.map 。使用 Array.map （它对数组起作用）。

I'm trying to use F#'s List.map function to call a function I've written on every string in the array. Here is the function I've written

(*Takes a string and filters it down to common text characters*)
let filterWord wordToFilter = 
    Regex.Replace(wordToFilter, "[^a-zA-Z0-9/!\'?.-]", "");

and here is my main method where I call it

(*Main method of the program*)
[<EntryPoint>]
let main argsv =
    let input = File.ReadAllText("Alice in Wonderland.txt"); //Reads all the text into a single string
    let unfilteredWords = input.Split(' ');
    let filteredWords = unfilteredWords |> List.map(fun x -> filterWord(x));
    0;

The problem is I am getting a syntax error at my List.map call saying

Error       Type mismatch. Expecting a
    string [] -> 'a    
but given a
    'b list -> 'c list    
The type 'string []' does not match the type ''a list'  

Changing input.split to a hard coded string array fixes the error so it has something to do with F# not realizing the result of input.split can be used with the map function as it's a string array. I just don't know how to change the code so it accomplishes what I want to accomplish. I'm relatively new to F# so any help I can get would be greatly appreciated!

解决方案

F# not realizing the result of input.split can be used with the map function as it's a string array

List.map works on lists, so F# realizes the result can't be used with List.map. Use Array.map (which works on arrays) instead.

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