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  • 【Rust】宏DRY

    环境

    • Rust 1.56.1
    • VSCode 1.61.2

    概念

    参考:https://doc.rust-lang.org/rust-by-example/macros/dry.html

    示例

    DRY 表示 Don't Repeat Yourself,不要重复你自己,意思是尽量不要写重复的代码。

    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);
    }
    

    总结

    了解了 Rust 中使用宏去实现一些重复的代码。

    附录

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  • 原文地址:https://www.cnblogs.com/jiangbo44/p/15727389.html
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