fn double(x: i64) -> i64 { x * 2 }
fn add(a: i64, b: i64) -> i64 { a + b }
fn clamp(lo: i64, hi: i64, x: i64) -> i64 {
    if x < lo { lo } else if x > hi { hi } else { x }
}

fn main() {
    let n = 3 |> double |> add(10) |> clamp(0, 100)
    println!("answer: {}", n)
}

// A request router - the heart of a web service, runnable right here.
fn route(method: &String, path: &String) -> String {
    if method == &"GET" && path == &"/" { "200 Gossamer" }
    else if method == &"GET" && path == &"/health" { "200 ok" }
    else if method == &"POST" && path == &"/users" { "201 created" }
    else { "404 not found" }
}

let requests = [("GET", "/"), ("GET", "/health"), ("POST", "/users"), ("GET", "/x")]
for (m, p) in requests {
    println!("{} {} -> {}", m, p, route(&m, &p))
}

fn fib(n: i64) -> i64 {
    if n < 2 { n } else { fib(n - 1) + fib(n - 2) }
}

fn main() {
    // spawn runs fib on a goroutine; join collects its result.
    let h = spawn(|| fib(30))
    match h.join() {
        Ok(v)  => println!("fib(30) on a goroutine = {}", v),
        Err(e) => eprintln!("worker failed: {}", e),
    }
}

use std::strings

enum Shape {
    Circle(f64),
    Rect { w: f64, h: f64 },
    Triangle(f64, f64),
}

fn area(s: &Shape) -> f64 {
    match s {
        Shape::Circle(r)       => 3.14159 * r * r,
        Shape::Rect { w, h }   => w * h,
        Shape::Triangle(b, h)  => 0.5 * b * h,
    }
}

// Top-level statements - no fn main() needed
let shapes = [Shape::Circle(3.0), Shape::Rect { w: 4.0, h: 5.0 }, Shape::Triangle(6.0, 2.0)]
for s in shapes {
    println!("area = {:.2}", area(&s))
}