【Rust】巨集-DRY
阿新 • • 發佈:2021-12-24
環境
- Rust 1.56.1
- VSCode 1.61.2
概念
參考:https://doc.rust-lang.org/rust-by-example/macros/dry.html
示例
DRY 表示 Don't Repeat Yourself
,不要重複你自己,意思是儘量不要寫重複的程式碼。
main.rs
use std::ops::{Add, Mul, Sub}; macro_rules! assert_equal_len { ($a:expr, $b:expr, $func:ident, $op:tt) => { assert!( $a.len() == $b.len(), "{:?}: dimension mismatch: {:?} {:?} {:?}", stringify!($func), ($a.len(),), stringify!($op), ($b.len(),) ); }; } macro_rules! op { ($func:ident, $bound:ident, $op:tt, $method:ident) => { fn $func<T: $bound<T, Output = T> + Copy>(xs: &mut Vec<T>, ys: &Vec<T>) { assert_equal_len!(xs, ys, $func, $op); for (x, y) in xs.iter_mut().zip(ys.iter()) { *x = $bound::$method(*x, *y); // *x = x.$method(*y); } } }; } fn main() {} // Implement `add_assign`, `mul_assign`, and `sub_assign` functions. op!(add_assign, Add, +=, add); op!(mul_assign, Mul, *=, mul); op!(sub_assign, Sub, -=, sub); mod test { use std::iter; macro_rules! test { ($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); }
總結
瞭解了 Rust 中使用巨集去實現一些重複的程式碼。