rust polymorphism

hello.rs

extern mod std;

enum Drawable {
  Rectangle(uint, uint, bool),
  Triangle(uint, bool)
}

fn draw_triangle(height: uint, empty: bool) {
  let mut n = 1;
  info!("Drawing %s triangle", (match empty {true => "empty", false => "full"}));
  while n <= height {
    let mut m = 1;
    while m <= n {
      if !empty || n == 1 || n == height || m == 1 || m == n {
        io::print("*");
      } else {
        io::print(" ")
      }

      m += 1;
    }
    io::println("");
    n += 1;
  }
}

fn draw_rectangle(width: uint, height: uint, empty: bool) {
  let mut n = 1;
  info!("Drawing %s rectangle", (match empty {true => "empty", false => "full"}));
  while n <= height {
    let mut m = 1;
    while m <= width {
      if !empty || n == 1 || n == height || m == 1 || m == width {
        io::print("*");
      } else {
        io::print(" ");
      }
      m += 1;
    }
    io::println("");
    n += 1;
  }
}

impl Drawable {
  fn draw(&self) {
    match *self {
      Triangle(height, empty) => draw_triangle(height, empty),
      Rectangle(width, height, empty) => draw_rectangle(width, height, empty)
    }
  }
}

fn main() {
  let drawables : ~[@Drawable] = ~[@Triangle(5, false), @Rectangle(8, 4, true), @Triangle(8, true)];
  for drawables.each |drawable| {
    drawable.draw();
    io::println("");
  }
}

out

$ rustc hello.rs && RUST_LOG=hello ./hello
rust: ~"Drawing full triangle"
*
**
***
****
*****

rust: ~"Drawing empty rectangle"
********
*      *
*      *
********

rust: ~"Drawing empty triangle"
*
**
* *
*  *
*   *
*    *
*     *
********