Rust-Programming-Cookbook/Chapter06/dry-macros/src/lib.rs

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1.6 KiB
Rust

use std::ops::{Add, Mul, Sub};
macro_rules! assert_equal_len {
// The `tt` (token tree) designator is used for
// operators and tokens.
($a:ident, $b: ident, $func:ident) => (
assert_eq!($a.len(), $b.len(),
"{:?}: dimension mismatch: {:?} {:?}",
stringify!($func),
($a.len(),),
($b.len(),));
)
}
macro_rules! op {
($func:ident, $bound:ident, $method:ident) => (
pub fn $func<T: $bound<T, Output=T> + Copy>(xs: &mut Vec<T>, ys: &Vec<T>) {
assert_equal_len!(xs, ys, $func);
for (x, y) in xs.iter_mut().zip(ys.iter()) {
*x = $bound::$method(*x, *y);
}
}
)
}
// Implement `add_assign`, `mul_assign`, and `sub_assign` functions.
op!(add_assign, Add, add);
op!(mul_assign, Mul, mul);
op!(sub_assign, Sub, sub);
#[cfg(test)]
mod test {
use std::iter;
macro_rules! test {
($func: ident, $x:expr, $y:expr, $z:expr) => {
#[test]
fn $func() {
for size in 0usize..10 {
let mut x: Vec<_> = iter::repeat($x).take(size).collect();
let y: Vec<_> = iter::repeat($y).take(size).collect();
let z: Vec<_> = iter::repeat($z).take(size).collect();
super::$func(&mut x, &y);
assert_eq!(x, z);
}
}
}
}
// Test `add_assign`, `mul_assign` and `sub_assign`
test!(add_assign, 1u32, 2u32, 3u32);
test!(mul_assign, 2u32, 3u32, 6u32);
test!(sub_assign, 3u32, 2u32, 1u32);
}