Checked<T> type for more ergonomic checked integer arithmetic

checked.rs

use std::fmt;

struct Checked<T>(T);

impl<T: fmt::Show> fmt::Show for Checked<T> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let Checked(ref s) = *self;
        s.fmt(f)
    }
}

impl<T: CheckedAdd> Add<Checked<T>, Checked<T>> for Checked<T> {
    fn add(&self, other: &Checked<T>) -> Checked<T> {
        let Checked(ref s) = *self;
        let Checked(ref o) = *other;
        Checked(s.checked_add(o).expect("addition failed"))
    }
}

impl<T: CheckedSub> Sub<Checked<T>, Checked<T>> for Checked<T> {
    fn sub(&self, other: &Checked<T>) -> Checked<T> {
        let Checked(ref s) = *self;
        let Checked(ref o) = *other;
        Checked(s.checked_sub(o).expect("subtraction failed"))
    }
}

impl<T: CheckedMul> Mul<Checked<T>, Checked<T>> for Checked<T> {
    fn mul(&self, other: &Checked<T>) -> Checked<T> {
        let Checked(ref s) = *self;
        let Checked(ref o) = *other;
        Checked(s.checked_mul(o).expect("multiplication failed"))
    }
}

impl<T: CheckedDiv> Div<Checked<T>, Checked<T>> for Checked<T> {
    fn div(&self, other: &Checked<T>) -> Checked<T> {
        let Checked(ref s) = *self;
        let Checked(ref o) = *other;
        Checked(s.checked_div(o).expect("division failed"))
    }
}

fn main() {
    let a = Checked(250u8);
    let b = Checked(5);
    let c = a + b;
    let c = c - b;
    let c = c / Checked(2);
    let c = c * Checked(2);
    println!("{}", c);
}