Fsharp

Command line

dotnet fsi # start F# Interactive dotnet fsi script.fsx # run script.fsx dotnet new console -o fsharp1 -lang f#

printf

let s = "value" printfn "text %A text" s

Format	Type
%A	any
%s	string
%i	integer
%b	boolean

String

let s = "abcde" // slice s[1..3] // "bcd" // triple-quote string allows to use double-quote within the string let s = """<tag attribute="value" />""" // concat strings let sb = StringBuilder() sb.Append("abc") sb.Append("def")

Collection

List

Ordered, immutable, series of elements of the same type.

let list1 = [1; 2; 3] let list2 = [1..5] // [1; 2; 3; 4; 5] let list3 = [0..2..10] // [0; 2; 4; 6; 8; 10] // elements in lists are not mutable // cons operator 0 :: list1 // create a new list with 0 at the head [0; 1; 2; 3] // extract head and tail let head :: tail = list1 // head: 1, tail: [2; 3] // concatenate operator list1 @ [4; 5] // create a new list [1; 2; 3; 4; 5]

Array

Fixed-sized, zero-based, mutable collectionof consecutive elements of the same type.

let myArray = [|1; 2; 3|] // elements in arrays are mutable myArray[1] <- 4 // [|1; 4; 3|]

Composite data type

Tuple

let tuple1 = (1, "one") let (a, b) = tuple1 // a: 1, b: "one"

Record

type Item = { Id: int; Name: string; } let item1 = { Id = 1; Name = "one" }

Function

let myFunction (param1: int) (param2: int) = let result = param1 + param2 result myFunction 1 2 // 3

Unit

Function which doesn't return any value.

let myUnit (param1: int) (param2: int) = let result = param1 + param2 printfn "%i" result () // useless because printfn is already a unit myUnit 1 2 // 3

Console input

printf "Enter a value: " let input = Console.ReadLine() printfn "Entered value: %s" input

.vscode/launch.json

{ "configurations": [ { "console": "integratedTerminal" // // switch from internalConsole to integratedTerminal to allow console input in VS code } ] }

Dev env

• VScode
  • Ionide for F# extension → intellisense
  • fantomas-fmt → format F#

Create launch and tasks

1. Disable the Ionide for F# extension
2. Run → Run Without Debugging
3. Select environment: .NET 5+ and .NET Core (this create the launch.json file)
4. Open launch.json → Add Configuration → .NET: Launch .NET Core Console App
5. Fill target-framework = net6.0 and project-name = myproject
6. Run → Run Without Debugging
7. Configure Task → Create tasks.json file from template → Select a Task Template: .NET Core