q.rs

use std::io;

macro_rules! Q(($M:ident, $T:ident, $S:ty, $L:ty, $Q:expr) => (mod $M {
    pub struct $T { value: $S }
    
    static K:$L = 1 << ($Q - 1);
    
    impl $T {
        pub fn init(value: $S) -> $T {
            $T { value: value }
        }

        pub fn to_s(&self) -> ~str {
            fmt!("%?", (self.value as float) / ($Q as float).exp2())
        }
    }

    impl Neg<$T> for $T {
        fn neg(&self) -> $T {
          $T { value: -self.value }
        }
    }

    impl Add<$T, $T> for $T {
        fn add(&self, rhs: &$T) -> $T {
            $T { value: self.value + rhs.value }
        }
    }

    impl Sub<$T, $T> for $T {
        fn sub(&self, rhs: &$T) -> $T {
            $T { value: self.value - rhs.value }
        }
    }

    impl Mul<$T, $T> for $T {
        fn mul(&self, rhs: &$T) -> $T {
            $T { value: (((self.value as $L) * (rhs.value as $L) + K) >> $Q) as $S }
        }
    }

    impl Div<$T, $T> for $T {
        fn div(&self, rhs: &$T) -> $T {
            $T { value: ((((self.value as $L) << $Q) + ((rhs.value as $L) / 2)) / (rhs.value as $L)) as $S }
        }
    }
}))

Q!(FixedPoint, Q7, i8, i16, 7)

fn main() {
    let a = FixedPoint::Q7::init(12);
    let b = FixedPoint::Q7::init(-19);

    io::println(fmt!("Add %s + %s = %s", a.to_s(), b.to_s(), (a + b).to_s()));
    io::println(fmt!("Sub %s - %s = %s", a.to_s(), b.to_s(), (a - b).to_s()));
    io::println(fmt!("Mul %s * %s = %s", a.to_s(), b.to_s(), (a * b).to_s()));
    io::println(fmt!("Div %s / %s = %s", a.to_s(), b.to_s(), (a / b).to_s()));
}