hello_world.rs

trait Filter {
  fn apply(&self, s: &str) -> ~str;
}

struct HelloFilter;

impl Filter for HelloFilter {
  fn apply(&self, s: &str) -> ~str { "Hello, " + s }
}

struct EnthusiasmFilter;

impl Filter for EnthusiasmFilter {
  fn apply(&self, s: &str) -> ~str { s + "!" }
}

fn main() {
  let who = ~"World";
  let filters: &[@Filter] = &[
    @HelloFilter as @Filter,
    @EnthusiasmFilter as @Filter
  ];

  println(filters.iter().fold(who, |v, f| f.apply(v)));
}