trait DuckLike {
  fn quack(&self);

  fn walk(&self) {
    println!("walking");
  }
}

struct Duck;

impl DuckLike for Duck {
  fn quack(&self) {
    println!("quack");
  }
}

impl DuckLike for i64 {
  fn quack(&self) {
    for _ in 0..*self {
      println!("quack");
    }
  }
}

//generics type parameters that "parameter: trait" makes boundary
fn duck_go<D: DuckLike>(duck: D) {
  duck.quack();
  duck.walk();
}

fn main() {
  let duck = Duck;
  let f = 0.0;
  duck_go(duck);
  //duck_go(f);
  //float does not implement DuckLile therefore, f is not be a parameter
}