lux/examples/generics.lux

// Demonstrating generic type parameters in Lux
//
// Expected output:
// identity(42) = 42
// identity("hello") = hello
// first(MkPair(1, "one")) = 1
// second(MkPair(1, "one")) = one
// map(Some(21), double) = Some(42)

// Generic identity function
fn identity<T>(x: T): T = x

// Generic pair type
type Pair<A, B> =
    | MkPair(A, B)

fn first<A, B>(p: Pair<A, B>): A =
    match p {
        MkPair(a, _) => a
    }

fn second<A, B>(p: Pair<A, B>): B =
    match p {
        MkPair(_, b) => b
    }

// Generic map function for Option
fn mapOption<T, U>(opt: Option<T>, f: fn(T): U): Option<U> =
    match opt {
        None => None,
        Some(x) => Some(f(x))
    }

// Helper function for testing
fn double(x: Int): Int = x * 2

// Test usage
let id_int = identity(42)
let id_str = identity("hello")

let pair = MkPair(1, "one")
let fst = first(pair)
let snd = second(pair)

let doubled = mapOption(Some(21), double)

fn showOption(opt: Option<Int>): String =
    match opt {
        None => "None",
        Some(x) => "Some(" + toString(x) + ")"
    }

fn printResults(): Unit with {Console} = {
    Console.print("identity(42) = " + toString(id_int))
    Console.print("identity(\"hello\") = " + id_str)
    Console.print("first(MkPair(1, \"one\")) = " + toString(fst))
    Console.print("second(MkPair(1, \"one\")) = " + snd)
    Console.print("map(Some(21), double) = " + showOption(doubled))
}

let output = run printResults() with {}