fn apply(f: fn(Int): Int, x: Int): Int = f(x)

fn compose(f: fn(Int): Int, g: fn(Int): Int): fn(Int): Int = fn(x: Int): Int => f(g(x))

fn double(x: Int): Int = x * 2

fn addOne(x: Int): Int = x + 1

fn square(x: Int): Int = x * x

let result1 = apply(double, 21)

let doubleAndAddOne = compose(addOne, double)

let result2 = doubleAndAddOne(5)

let result3 = square(addOne(double(5)))

fn add(a: Int): fn(Int): Int = fn(b: Int): Int => a + b

let add5 = add(5)

let result4 = add5(10)

fn multiply(a: Int, b: Int): Int = a * b

let times3 = fn(x: Int): Int => multiply(3, x)

let result5 = times3(7)

let transform = fn(record: { x: Int, y: Int }): Int => record.x + record.y

let point = { x: 10, y: 20 }

let recordSum = transform(point)

fn printResults(): Unit with {Console} = {
    Console.print("apply(double, 21) = " + toString(result1))
    Console.print("compose(addOne, double)(5) = " + toString(result2))
    Console.print("pipe: 5 |> double |> addOne |> square = " + toString(result3))
    Console.print("curried add5(10) = " + toString(result4))
    Console.print("partial times3(7) = " + toString(result5))
    Console.print("record transform = " + toString(recordSum))
}

let output = run printResults() with {}
