test "math operations" {
    assert(1 + 1 == 2)
    assert_eq(3 * 3, 9)
}

test "string methods" {
    assert_eq("hello".upper(), "HELLO")
    assert_eq("hello".len(), 5)
}

fn greet(name: string = "world") -> string {
    return "hello ${name}"
}

test "default parameters" {
    assert_eq(greet(), "hello world")
    assert_eq(greet("wyn"), "hello wyn")
}

fn main() {
    // List comprehensions
    var squares = [x * x for x in 0..10]
    var evens = [x for x in 0..20 if x % 2 == 0]

    // Slice syntax
    var first3 = squares[0:3]          // [0, 1, 4]
    var hello = "hello world"[0:5]   // "hello"

    // Functional chains
    var data = [1, 2, 3, 4, 5]
    var result = data
        .filter(fn(x: int) -> int { return x > 2 })
        .map(fn(x: int) -> int { return x * 10 })
    println(result.join(", "))       // 30, 40, 50
}

trait Drawable {
    fn draw(self) -> string
}

struct Circle { r: int }
struct Rect { w: int, h: int }

impl Drawable for Circle {
    fn draw(self) -> string { return "circle" }
}
impl Drawable for Rect {
    fn draw(self) -> string { return "rect" }
}

// Dynamic dispatch — any Drawable
fn render(shape: Drawable) { println(shape.draw()) }

fn safe_div(a: int, b: int) -> ResultInt {
    if b == 0 { return Err("divide by zero") }
    return Ok(a / b)
}

fn compute(n: int) -> int {
    var sum = 0
    for i in 0..n { sum = sum + i }
    return sum
}

fn main() {
    // Spawn 3 parallel tasks — 2μs each
    var f1 = spawn compute(100000)
    var f2 = spawn compute(200000)
    var f3 = spawn compute(300000)

    var total = await f1 + await f2 + await f3

    // Channels for message passing
    var ch = Task.channel(10)
    Task.send(ch, total)
    println(Task.recv(ch).to_string())
}

// Numbers
var answer = 42.to_string()          // "42"
var absolute = Math.abs(-5)          // 5
var power = Math.pow(2, 8)           // 256
var rounded = Math.round(3.7)        // 4

// Strings
var clean = "  hello world  "
    .trim().capitalize()              // "Hello world"

var shout = "hello"
    .upper().replace("L", "*").reverse()  // "O**EH"

// Arrow lambdas
var nums = [1, 2, 3, 4, 5]
var doubled = nums.map(fn(x) => x * 2)       // [2,4,6,8,10]
var big = nums.filter(fn(x) => x > 3)        // [4,5]

// Chain everything
var result = "HELLO"
    .lower().capitalize().len()
    .to_string()                          // "5"

fn main() {
    // Fetch + parse + store in 10 lines
    var body = Http.get("https://api.example.com/users")
    var doc = Json.parse(body)
    var name = Json.get(doc, "name")

    var token = Encoding.base64_encode("user:secret")
    var hash = Crypto.sha256(body)

    var db = Db.open("app.db")
    Db.exec(db, "INSERT INTO users(name) VALUES('${name}')")

    var csv = Csv.parse(File.read("data.csv"))
    println("Saved ${name}")
}