F# and open source

Multiple items
module List

from Microsoft.FSharp.Collections

--------------------
type List<'T> =
  | ( [] )
  | ( :: ) of Head: 'T * Tail: 'T list
  interface IEnumerable
  interface IEnumerable<'T>
  member Head : 'T
  member IsEmpty : bool
  member Item : index:int -> 'T with get
  member Length : int
  member Tail : 'T list
  static member Cons : head:'T * tail:'T list -> 'T list
  static member Empty : 'T list

Full name: Microsoft.FSharp.Collections.List<_>

val sum : list:'T list -> 'T (requires member ( + ) and member get_Zero)

Full name: Microsoft.FSharp.Collections.List.sum

val printfn : format:Printf.TextWriterFormat<'T> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.printfn

val square : x:int -> int

Full name: Document.square

val x : int

val sq : int

Full name: Document.sq

type Person =
{First: string;
Last: string;}

Full name: Document.Person

Person.First: string

Multiple items
val string : value:'T -> string

Full name: Microsoft.FSharp.Core.Operators.string

--------------------
type string = System.String

Full name: Microsoft.FSharp.Core.string

Person.Last: string

type Employee =
| Worker of Person
| Manager of Employee list

Full name: Document.Employee

union case Employee.Worker: Person -> Employee

union case Employee.Manager: Employee list -> Employee

type 'T list = List<'T>

Full name: Microsoft.FSharp.Collections.list<_>

val jdoe : Person

Full name: Document.jdoe

val worker : Employee

Full name: Document.worker

Multiple items
val int : value:'T -> int (requires member op_Explicit)

Full name: Microsoft.FSharp.Core.Operators.int

--------------------
type int = int32

Full name: Microsoft.FSharp.Core.int

--------------------
type int<'Measure> = int

Full name: Microsoft.FSharp.Core.int<_>

namespace System

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F# and Open Source

Andrea Magnorsky

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Available on Steam Early Access

F# OSS and you

F# Open sourced 4 years ago. Announced by Don Syme
F# Software Foundation at fsharp.org
User groups growth
100+ pull requests for F# 4.0

Latest announcements, Big wins !

Great for language adoption
Visual Studio community with extensions
CLR in a package FTW

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// one-liners
[1..100] |> List.sum |> printfn "sum=%d"

// no curly braces, semicolons or parentheses
let square x = x * x
let sq = square 42 

// simple types in one line
type Person = {First:string; Last:string}

// complex types in a few lines
type Employee = 
  | Worker of Person
  | Manager of Employee list

// type inference
let jdoe = {First="John";Last="Doe"}
let worker = Worker jdoe

Visit F# for Fun and Profit for more examples

Some examples

Light syntax, POCOs

C#

public class Person
{
    public Person(string name, int age)
    {
        _name = name;
        _age = age;
    }

    private readonly string _name;
    private readonly int _age;

    public string Name
    {
        get { return _name; }
    }

    public int Age
    {
        get { return _age; }
    }
}

F#

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type Person( name:string, age:int) =

/// Full name
member person.Name = name

/// Age in years
member person.Age = age

Some examples

Testing

C#

using NUnit.Framework;

[TestFixture]
public class MathTest
{
    [Test]
    public void TwoPlusTwoShouldEqualFour()
    {
        Assert.AreEqual(2 + 2, 4);
    }
}

F#

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module MathTest =

open NUnit.Framework

let [<Test>] ``2 + 2 should equal 4``() =
    Assert.AreEqual(2 + 2, 4)

FsCheck

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module MathTest =

open FsCheck.Nunit

[<Property>]
let ``Given a, a + a should equal a * 2`` ( a: int) =
    a + a = 2 * a

You can use FsCheck from F# and C#.

Some examples

C# <-> F# Interop

C# consuming F# code

Use namespaces in F# or prefix with global::YourModuleName

using System;
class Program
{
    static void Main(string[] args)
    {
        var s = Calculator.Calc.add("4 4", "+");
        Console.WriteLine("The sum is {0}", s);
    }
}

and the F# side

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namespace Calculator
module Calc =

    open System
    let add numbers delimiter =    
        // Do stuff to add numbers

F# consuming C# code

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module MathTest =

open NUnit.Framework

let [<Test>] ``2 + 2 should equal 4``() =
    Assert.AreEqual(2 + 2, 4)

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