F#

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Language Features

Basics

Type inference

"Hello, World!"

val it: string = "Hello, World!"

let myInt = 9

val myInt: int = 9

Lists

Commas are never user as delimiters, only semicolons

let firstList = [1; 2; 3]

val firstList: int list = [1; 2; 3]

[1..5]

val it: int list = [1; 2; 3; 4; 5]

List Comprehensions

[for i in 1..10 do i * i]

val it: int list = [1; 4; 9; 16; 25; 36; 49; 64; 81; 100]

Functions

let square x = x * x
square 4

val square: x: int -> int
val it: int = 16

let add x y = x + y
add 2 3

val add: x: int -> y: int -> int
val it: int = 5

Anonymous Functions

List.map (fun x -> x * x) [1; 2; 3]

val it: int list = [1; 4; 9]

Pattern Matching

let x = "a"
match x with
 | "a" -> "x is a"
 | "b" -> "x is b"
 | _ -> "x is neither"

val x: string = "a"
val it: string = "x is a"

Pipe Operator

firstList |> List.map square

val it: int list = [1; 4; 9]

firstList |> List.map square |> List.sum

val it: int = 14

Backwards Pipe

List.sum <| [1; 2; 3; 4]

val it: int = 10

Resources

Announcing F# 8

List of F# 8 new features: https://devblogs.microsoft.com/dotnet/announcing-fsharp-8/