如何使用函数式方法执行正则表达式？

Question

如何使用函数式方法处理正则表达式？目前我希望用户输入一个输入，即使他们以大写字母输入，它仍然会给出响应？我不确定如何实现这一点。

open System
open System.Drawing 
open System.Windows.Forms

let (|Hello|Bye|None|) input =
match input with
    | "hello" | "hi" | "morning" 
            -> Hello
    | "Goodbye" | "bye" | "go"
            -> Bye
    | _     
            -> None

   let rand = new Random()

   let hello_response () =
   let n = rand.Next(10) 
   match n with
    | 0 -> "How do you do."
    | 1 -> "Is nice talking to you."
    | 2 -> "Tell me something new."
    | 3 -> "Nice to meet you."
    | 4 -> "My pleasure."
    | 5 -> "Hi."
    | 6 -> "Hello."
    | 7 -> "Good day."
    | 8 -> "Salutation!"
    | 9 -> "Welcome!"


    let good_bye_response () =
    let n = rand.Next(10) 
    match n with
    | 0 -> "Talk to you soon."
    | 1 -> "It was nice talking to you."
    | 2 -> "Good bye."
    | 3 -> "Stay a bit longer."
    | 4 -> "Adios amigo."
    | 5 -> "Bye."
    | 6 -> "Adios."
    | 7 -> "See you."
    | 8 -> "Please don't go"
    | 9 -> "Why are you leaving me alone?"

    let none_response (str:string) =
    let n = rand.Next(10) 
    match n with
    | 0 -> "Maybe."
    | 1 -> "Perhaps " + str 
    | 2 -> "Yes."
    | 3 -> "Ah!"
    | 4 -> "Whatever." 
    | 5 -> "Sorry, the chat closed unexpectedly. What was your last 
    question?"
    | 6 -> "Where were we? I losed track of the conversation."
    | 7 -> "Very interesting"
    | 8 -> "Wow!"
    | 9 -> "Mmmmmm!"

    let rec response (token: string) (str: string) =
    match token with
    | Hello
        -> hello_response ()
    | Bye
        -> good_bye_response ()
    | "" 
        -> none_response str
    | None when (str.IndexOf(" ") > 0) 
        -> response (str.Substring(0,str.IndexOf(" "))) 
    (str.Substring(str.IndexOf(" ")+1))
    | None when (str.IndexOf(" ") < 0) 
        -> response str ""
    | None 
        -> str

    let marketbot_resp (str: string) =
    if (str.IndexOf(" ") > 0) then
    response (str.Substring(0,str.IndexOf(" "))) 
    (str.Substring(str.IndexOf(" ")+1)) + "\n"
    else
    response str "" + "\n"

Answer 1

您可以在 F# 中使用正则表达式，就像在 C# 或 VB.NET（或任何其他 .NET 语言）中使用正则表达式一样。 MSDN 提供了有关该主题的相当广泛的文档。 检查一下。

根类是

System.Text.RegularExpressions.Regex

。最简单的匹配方法是通过

IsMatch

静态方法：

let (|Hello|Bye|None|) input =
    if Regex.IsMatch( input, "(?i)hello|hi|morning" ) then Hello
    elif Regex.IsMatch( input, "(?i)goodbye|bye|go" ) then Bye
    else None

您还可以通过创建

Regex

的实例并重用它来“缓存”正则表达式。这将为您节省一点点性能：

let (|Hello|Bye|None|) =
    let hello = Regex "(?i)hello|hi|morning"
    let bye = Regex "(?i)goodbye|bye|go"
    fun input ->
        if hello.IsMatch input then Hello
        elif bye.IsMatch input then Bye
        else None

但是，对于这个特定的任务，我认为正则表达式有点矫枉过正。我只是在匹配之前将字符串转换为小写：

let (|Hello|Bye|None|) (input: string) =
    match input.ToLower() with
    | "hello" | "hi" | "morning" 
            -> Hello
    | "goodbye" | "bye" | "go"
            -> Bye
    | _     
            -> None