shapes.rs

// you can't subclass, I'll use an example where each object has its own position instead

// be careful: this code sucks, compile with "rustc shapes.rs"

// a Point will be a "tuple struct" because I like the idea
struct Point(int, int); // xpos and ypos in your C++

// Points are "ToStr"ingable but not Drawable in my program
impl ToStr for Point {
	fn to_str(&self) -> ~str {
		// you must use match to extract values from tuples or something
		// refs are scary in Rust so read the tutorial, I don't know what I am doing
		match *self {
			Point(x, y) => format!("Point({}, {})", x, y)
		}
	}
}

// the Drawable trait that each shape will have to implement
trait Drawable {
	fn draw(&self) -> bool;
}

// a Rectangle with uint instead of size_t, but you can specify u16, u32, u64... instead
// also it has a Point for its position because it's fun
struct Rectangle {
	position: Point,
	width: uint,
	height: uint
}

impl Rectangle {
	// there are no constructors in Rust, but they are almost always named new or new_something. They have considered adding a Drop trait for destructors though
	fn new(x: int, y: int, w: uint, h: uint) -> Rectangle {
		Rectangle { position: Point(x, y), width: w, height: h }
	}

	// only one name for each method...
	fn new_with_size(w: uint, h: uint) -> Rectangle {
		Rectangle { position: Point(0, 0), width: w, height: h }
	}

	// be careful, I don't understand all the pointers and refs of Rust, maybe you could change "p" to be a &Point or something
	fn new_with_point(p: Point) -> Rectangle {
		Rectangle { position: p, width: 0, height: 0 }
	}
}

// a Rectangle can be drawn now, wonderful!
impl Drawable for Rectangle {
	fn draw(&self) -> bool {
		// you shouldn't need to write position.to_str(), there has to be a module like fmt to do that automatically from the compiler
		println(format!("I am a rectangle at {} with size ({}, {})", self.position.to_str(), self.width, self.height));
		return true;
	}
}

fn main() {
	let r: Rectangle = Rectangle::new(10, 10, 640, 480);
	r.draw();
}

// that's all folks!