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F#

An open-source, cross-platform functional programming language for .NET

Get Started with F#

Supported on Windows, Linux, and macOS

// 'name' is inferred to be a string based on usage.
let printMessage name =
    printfn "Hello there, %s!\n" name

// 'names' is inferred to be a sequence of strings.
let printNames names =
    names
    |> Seq.iter printMessage

let names = [ "Ana"; "Felipe"; "Emillia" ]
printNames names
                                     
let square x = x * x
let isOdd x = x % 2 <> 0

let sumOfOddSquares nums =
    nums
    |> List.filter isOdd
    |> List.sumBy square

let numbers = [1; 2; 3; 4; 5]
let sum = sumOfOddSquares numbers

printfn "The sum of the odd squares in %A is %d" numbers sum
type Shape =
    | Square of side: double
    | Rectangle of width: double * length: double

let getArea shape =
    match shape with
    | Square side -> side * side
    | Rectangle (width, length) -> width * length

let square = Square 2.0
printfn "The area of the square is %f" (getArea square)
                                   
type Customer(firstName, middleInitial, lastName) = 
    member this.FirstName = firstName
    member this.MiddleInitial = middleInitial
    member this.LastName = lastName

    member this.SayFullName() =
        this.FirstName + " " + this.MiddleInitial + " " + this.LastName

let customer = Customer("Emillia", "C", "Miller")

printfn "Hello, I'm %s!" (customer.SayFullName())
                                   

Functional-first

F# is a functional-first language with features and idioms for both functional and object-oriented programming. It has been designed for functional programming on .NET while also offering clean interop with C# and existing codebases.

Professional tooling, everywhere

High quality editors for Windows, Linux, and macOS all run on a single F# compiler, providing consistent high quality features.

Learn about tools for F#

Microsoft + Community

F# is an open source language and Microsoft is a leading contributor. The independent F# Software Foundation provides a central place for the F# community to grow and learn together.

F# Software Foundation website

Runs on .NET

F# is part of the .NET developer platform. Use your skills, code, and favorite libraries to build all types of apps.

Learn about the .NET platform

Ready to Get Started?

Our step-by-step tutorial will help you get F# running on your computer.

Supported on Windows, Linux, and macOS

Get Started