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Accepted
Olivier Lasne
Asked: 2024-09-15 03:22:59 +0800 CST

是否可以定义一个变量在算术运算中始终饱和？

  • 772

我有一个变量，我对它进行了很多算术运算。

我的代码是这样的：

let a: u32 = 3;
let res = (a*2) - 42

a当太低时就会溢出，所以我必须使用它saturating_sub()来解决问题：

let a: u32 = 3;
let res = (a * 2).saturating_sub(42);

这确实很有效，但saturating_sub可读性不如-。

由于我有很多这样的操作，而且在每种情况下，我都希望a饱和。我想知道是否可以定义应该a始终饱和。而不是用替换-每个saturate_sub。

rust

1 个回答

  1. Best Answer

    那是std::num::Saturating，但是它仅实现与其他的操作Saturating，而不是底层原语：

    let a = Saturating(3u32);
let res = (a * Saturating(2)) - Saturating(42);

    如果这对你来说是一个问题，你可以创建自己的类型：

    use std::num::Saturating as StdSaturating;
use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};

#[derive(Clone, Copy, Debug)]
pub struct Saturating<T>(pub T);

macro_rules! impl_saturating_op {
    ( $trait:ident, $method:ident, $trait_assign:ident, $method_assign:ident => $($ty:ty),* ) => {
        $(
            impl $trait for Saturating<$ty> {
                type Output = Saturating<$ty>;
                fn $method(self, other: Saturating<$ty>) -> Self::Output {
                    Saturating(StdSaturating(self.0).$method(StdSaturating(other.0)).0)
                }
            }

            impl $trait<$ty> for Saturating<$ty> {
                type Output = Saturating<$ty>;
                fn $method(self, other: $ty) -> Self::Output {
                    Saturating(StdSaturating(self.0).$method(StdSaturating(other)).0)
                }
            }

            impl $trait<Saturating<$ty>> for $ty {
                type Output = Saturating<$ty>;
                fn $method(self, other: Saturating<$ty>) -> Self::Output {
                    Saturating(StdSaturating(self).$method(StdSaturating(other.0)).0)
                }
            }

            impl $trait_assign for Saturating<$ty> {
                fn $method_assign(&mut self, other: Saturating<$ty>) {
                    self.0 = StdSaturating(self.0).$method(StdSaturating(other.0)).0;
                }
            }

            impl $trait_assign<$ty> for Saturating<$ty> {
                fn $method_assign(&mut self, other: $ty) {
                    self.0 = StdSaturating(self.0).$method(StdSaturating(other)).0;
                }
            }
        )*
    }
}

impl_saturating_op!(Add, add, AddAssign, add_assign => i8, i16, i32, i64, i128, isize, u8, u16, u32, u64, u128, usize);
impl_saturating_op!(Sub, sub, SubAssign, sub_assign => i8, i16, i32, i64, i128, isize, u8, u16, u32, u64, u128, usize);
impl_saturating_op!(Mul, mul, MulAssign, mul_assign => i8, i16, i32, i64, i128, isize, u8, u16, u32, u64, u128, usize);
impl_saturating_op!(Div, div, DivAssign, div_assign => i8, i16, i32, i64, i128, isize, u8, u16, u32, u64, u128, usize);

fn main() {
    let a = Saturating(3u32);
    let res = (a * 2) - 42;
}
    • 5

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