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F#

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F#
FsharpLanguageLogo.jpg
编程范型多范型: 函數程式語言, 指令式編程, 面向对象編程, 元编程, 并发计算
設計者微软研究院, Don Syme
實作者微软, The F# Software Foundation
发行时间2005年 (2005) (version 1.0)
穩定版本
5.0[1]在维基数据编辑
( 2020年11月10日,7個月前 )
型態系統静态类型, 强类型, 类型推论
作業系統跨平台 (.NET框架, Mono, JavaScript)
許可證Apache许可证
文件扩展名.fs, .fsi, .fsx, .fsscript
網站fsharp.org
啟發語言
ML, OCaml, C#, Python, Haskell,[2] Scala, Erlang
影響語言
F*, LiveScript

F#是由微软发展的为.NET语言提供运行环境的程序设计语言,是函數程式語言FP,Functional Programming),函數程式語言最重要的基礎是Lambda Calculus。它是基于OCaml的,而OCaml是基于ML函数程式语言。有時F#和OCaml的程式是可以交互編譯的。

F#已經接近成熟,支援高阶函数、柯里化惰性求值、Continuations、模式匹配、闭包、列表处理和元编程。这是一个用于显示.NET在不同编程语言间互通的程序设计,可以被.NET中的任意其它代碼編譯和調用。

2002年微软開始由Don Syme帶領研發F#,從C#,LINQHaskell中獲取了經驗,2005年推出第一個版本,2007年7月31日释出1.9.2.9版。2007年底,微軟宣布F#進入產品化的階段。

F#已被集成在Visual Studio 2010中,版本是2.0,含有对.Net Framework的完全支持。

F#现在在Visual Studio 2015中,版本是4.0。

F#现在在Visual Studio 2017中,版本是4.1。

范例[编辑]

一些小小范例如下:

// This is a comment for a sample hello world program.
printfn "Hello World!"

具有構造函數的Person類,該構造函數具有名稱和年齡以及兩個不可變的屬性。

/// This is a documentation comment for a type definition.
type Person(name : string, age : int) =
    member x.Name = name
    member x.Age = age
    
/// class instantiation
let mrSmith = Person("Smith", 42)

一个经常用于演示函数式语言语法的简单示例。此处以32位的阶乘函数为例,使用f# A simple example that is often used to demonstrate the syntax of functional languages is the factorial function for non-negative 32-bit integers, here shown in F#:

/// Using pattern matching expression
let rec factorial n =
    match n with
    | 0 -> 1
    | _ -> n * factorial (n - 1)

/// For a single-argument functions there is syntactic sugar (pattern matching function):
let rec factorial = function 
    | 0 -> 1 
    | n -> n * factorial (n - 1)
    
/// Using fold and range operator
let factorial n = [1..n] |> Seq.fold (*) 1

迭代示例:

/// Iteration using a 'for' loop
let printList lst = 
    for x in lst do
        printfn "%d" x

/// Iteration using a higher-order function
let printList2 lst = 
    List.iter (printfn "%d") lst

/// Iteration using a recursive function and pattern matching
let rec printList3 lst =
    match lst with
    | [] -> ()
    | h :: t ->
        printfn "%d" h
        printList3 t

斐波那契数列数列示例:

/// Fibonacci Number formula
let fib n =
    let rec g n f0 f1 =
        match n with
        | 0 -> f0
        | 1 -> f1
        | _ -> g (n - 1) f1 (f0 + f1)
    g n 0 1

/// Another approach - a lazy infinite sequence of Fibonacci numbers
let fibSeq = Seq.unfold (fun (a,b) -> Some(a+b, (b, a+b))) (0,1)

// Print even fibs
[1 .. 10]
|> List.map     fib
|> List.filter  (fun n -> (n % 2) = 0)
|> printList

// Same thing, using a list expression
[ for i in 1..10 do
    let r = fib i
    if r % 2 = 0 then yield r ]
|> printList

一个Windows程序样本示例:

// Open the Windows Forms library
open System.Windows.Forms

// Create a window and set a few properties
let form = new Form(Visible=true, TopMost=true, Text="Welcome to F#")

// Create a label to show some text in the form
let label =
    let x = 3 + (4 * 5)
    new Label(Text = sprintf "x = %d" x)

// Add the label to the form
form.Controls.Add(label)

// Finally, run the form
[<System.STAThread>]
Application.Run(form)

多线程编程示例(此处为CPU和I/O任务同时进行):

/// A simple prime number detector
let isPrime (n:int) =
   let bound = int (sqrt (float n))
   seq {2 .. bound} |> Seq.forall (fun x -> n % x <> 0)

// We are using async workflows
let primeAsync n =
    async { return (n, isPrime n) }

/// Return primes between m and n using multiple threads
let primes m n =
    seq {m .. n}
        |> Seq.map primeAsync
        |> Async.Parallel
        |> Async.RunSynchronously
        |> Array.filter snd
        |> Array.map fst

// Run a test
primes 1000000 1002000
    |> Array.iter (printfn "%d")

参考文献[编辑]

  1. ^ https://devblogs.microsoft.com/dotnet/announcing-f-5/。
  2. ^ Syme, Granicz & Cisternino (2007:2頁) "F# also draws from Haskell particularly with regard to two advanced language features called sequence expressions and workflows."

外部链接[编辑]