Rust-High-Performance/Chapter09/example4.rs

use std::ops::Mul;

#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub struct Amount {
    value: u64,
}

macro_rules! impl_mul_int {
    ($($t:ty)*) => ($(
        impl Mul<$t> for Amount {
            type Output = Self;

            fn mul(self, rhs: $t) -> Self::Output {
                Self { value: self.value * rhs as u64 }
            }
        }

        impl Mul<Amount> for $t {
            type Output = Amount;

            fn mul(self, rhs: Amount) -> Self::Output {
                Self::Output { value: self as u64 * rhs.value }
            }
        }
    )*)
}

impl_mul_int! { u8 u16 u32 u64 usize }

// Dummy main() function to make the compiler happy.
fn main() {}