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

List and arrays

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]

// arrays
let myArray = [|1; 2; 3|]

// elements in arrays are mutable
myArray[1] <- 4  // [|1; 4; 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

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