fsharp-learning/for-fun-and-profit/example.fsx

let myInt = 5
let myFloat = 3.14
let myString = "Hello"

let twoToFive = [2;3;4;5]
let oneToFive = 1 :: twoToFive // New first element
let zeroToFive = [0;1] @ twoToFive // Concatenation

let square x = x * x
square 3

let add x y = x + y
add 2 3

let evens list =
  let isEven x = x % 2 = 0 // Inline function
  List.filter isEven list // Basic libary function

evens oneToFive

let sumOfQuaresTo100 =
  List.sum ( List.map square [1..100] )

let sumOfSquaresTo100piped =
  [1..100] |> List.map square |> List.sum

let sumOfSquaresTo100WithFun =
  [1..100] |> List.map (fun x->x*x) |> List.sum // `fun` is like a lambda

// F# Functions return implicitly

let simplePatternMatch =
  let x = "a"
  match x with
   | "a" -> printfn "x is a"
   | "b" -> printfn "x is b"
   | _ -> printfn "x is something else"

let validValue = Some(99)
let invalidValue = None

let optionPatternMatch input =
  match input with
   | Some i -> printfn "Input is an int=%d" i // similar to c format strings
   | None -> printfn "Input missing"

optionPatternMatch validValue
optionPatternMatch invalidValue

// Stuff with data types
let twoTuple = 1,2
let threeTuple = "a",2,true

type Person = {First:string; Last:string} // Record types have named fields
let person1 = {First="john"; Last="roberts"}

type Temp = 
        | DegreesC of float
        | DegreesF of float

let temp = DegreesF 98.6

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

let worker = Worker person1

// Printing stuff out
printfn "Printing an int %i, a float %f, a bool %b" 1 2.0 true
printfn "A string %s, and something generic %A" "hello" [1;2;3;4]

// You can also print complex types that have been created
printfn "twoTuple=%A,\nPerson=%A,\nTemp=%A,\nEmployee=%A"
        twoTuple person1 temp worker