rust-default-methods-ex2.rs

enum Color { cyan, magenta, yellow, black }

impl Eq for Color {
    fn eq(&self, other: &Color) -> bool {
        match (*self, *other) {
            (cyan, cyan)       => { true  }
            (magenta, magenta) => { true  }
            (yellow, yellow)   => { true  }
            (black, black)     => { true  }
            _                  => { false }
        }
    }

    // Rust 0.7 needs this.
    fn ne(&self, other: &Color) -> bool { !self.eq(other) } 
}

// A bounded quantification example -- this is where traits are handy.
fn member<T: Eq>(elem: T, vec: ~[T]) -> bool {

    // 0.7 syntax:
    for vec.iter().advance |vec_elem| {
        
    // 0.8 syntax:
    // for vec_elem in vec.iter() {
        if elem == *vec_elem { return true; }
    }

    return false;
}

fn main() {
    println(fmt!("%?", member(magenta, ~[black, yellow, magenta, black])));
}