gistfile1.txt

extern mod std;

use io::WriterUtil;

const WIDTH: uint = 76;
const HEIGHT: uint = 10;
const NUM_BALLS: uint = 10;

struct Screen([[char * 76] * 10]);

impl Screen {
    fn print(&self) {
        io::print("\x1b[2J\x1b[;H");
        for self.each |row| {
            for row.each |&ch| {
                io::stdout().write_char(ch);
            }
            io::println("");
        }
    }

    fn paint(&mut self, x: int, y: int, b: char) {
        self[y][x] = b
    }
}

struct Ball {
    x: int, y: int,
    xd: int, yd: int
}

impl Ball {
    static fn new() -> Ball {
        Ball {
            x: rand::random() % WIDTH as int,
            y: rand::random() % HEIGHT as int,
            xd: (rand::random() % 2 * 2) as int - 1,
            yd: (rand::random() % 2 * 2) as int - 1,
        }
    }

    fn move_around(&mut self) {
        move_bounce(&mut self.x, &mut self.xd, WIDTH as int);
        move_bounce(&mut self.y, &mut self.yd, HEIGHT as int);
    }
}

fn move_bounce(v: &mut int, d: &mut int, max: int) {
    *v += *d;
    if *v < 0 {
        *v = -*v;
        *d = -*d;
    } else if *v >= max {
        *v = max - 2 - (*v - max);
        *d = -*d;
    }
}

fn main() {
    let mut balls = vec::from_fn(NUM_BALLS, |_i| Ball::new());
    loop {
        let mut screen = Screen([ [ ' ', ..76 ], ..10 ]);
        for vec::each_mut(balls) |ball| {
            ball.move_around();
            screen.paint(ball.x, ball.y, '*');
        }
        screen.print();
        std::timer::sleep(std::uv_global_loop::get(), 1000 / 20);
    }
}