如何在结构上实现ops::Mul，使其既适用于数字类型又适用于另一个结构

Question

我已经实现了一个Point3D结构：

use std::ops;
#[derive(Debug, PartialEq)]
pub struct Point3D {
pub x: f32,
pub y: f32,
pub z: f32,
}
impl ops::Add<&Point3D> for &Point3D {
type Output = Point3D;
fn add(self, rhs: &Point3D) -> Point3D {
Point3D {
x: self.x + rhs.x,
y: self.y + rhs.y,
z: self.z + rhs.z,
}
}
}
impl ops::Sub<&Point3D> for &Point3D {
type Output = Point3D;
fn sub(self, rhs: &Point3D) -> Point3D {
Point3D {
x: self.x - rhs.x,
y: self.y - rhs.y,
z: self.z - rhs.z,
}
}
}
impl ops::Mul<&Point3D> for &Point3D {
type Output = f32;
fn mul(self, rhs: &Point3D) -> f32 {
self.x * rhs.x + self.y * rhs.y + self.z * rhs.z
}
}
//Scalar impl of ops::Mul here
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn addition_point_3D() {
let point1 = Point3D {
x: 1.0,
y: 2.0,
z: 3.0,
};
let point2 = Point3D {
x: 4.0,
y: 5.0,
z: 6.0,
};
let result = &point1 + &point2;
assert_eq!(
result,
Point3D {
x: 5.0,
y: 7.0,
z: 9.0
},
"Testing Addition with {:?} and {:?}",
point1,
point2
);
}
#[test]
fn subtraction_point_3D() {
let point1 = Point3D {
x: 1.0,
y: 2.0,
z: 3.0,
};
let point2 = Point3D {
x: 4.0,
y: 5.0,
z: 6.0,
};
let result = &point1 - &point2;
assert_eq!(
result,
Point3D {
x: -3.0,
y: -3.0,
z: -3.0
},
"Testing Subtraction with {:?} and {:?}",
point1,
point2
);
}
#[test]
fn point3D_point3D_multiplication() {
let point1 = Point3D {
x: 1.0,
y: 2.0,
z: 3.0,
};
let point2 = Point3D {
x: 4.0,
y: 5.0,
z: 6.0,
};
let result = &point1 * &point2;
assert_eq!(
result, 32.0,
"Testing Multiplication with {:?} and {:?}",
point1, point2
);
}
/*
#[test]
fn point3D_scalar_multiplication() {
let point1 = Point3D { x: 1.0, y: 2.0, z: 3.0};
let scalar = 3.5;
let result = &point1 * &scalar;
assert_eq!(result, Point3D { x: 3.5, y: 7.0, z: 10.5 }, "Testing Multiplication with {:?} and {:?}", point1, scalar);
}
*/
}

我想在乘法特性中使用泛型，这样，如果我给它传递另一个Point3D类，它将实现点积，但如果我给他传递一个基本数字类型(integer，f32，unsigned integer，f64(，它将用标量值乘以x、y和z。我该怎么做？

Answer 1

你的意思是这样的吗？

impl ops::Mul<f32> for &Point3D {
type Output = Point3D;
fn mul(self, rhs: f32) -> Point3D {
Point3D {
x: self.x * rhs,
y: self.y * rhs,
z: self.z * rhs
}
}
}

这将允许您执行以下操作：

let point = Point3D { x: 1.0, y: 2.0, z: 3.0};
let result = &point * 4.0;

Answer 2

要使用泛型，首先需要使Point3D结构接受泛型，如

use std::ops::{Mul, Add};
#[derive(Debug, PartialEq)]
pub struct Point3D<T> {
pub x: T,
pub y: T,
pub z: T,
}

Point3D与数字类型相乘的实现将是

impl<T> Mul<T> for &Point3D<T>
where T: Mul<Output=T> + Copy
{
type Output = Point3D<T>;
fn mul(self, rhs: T) -> Self::Output {
Point3D {
x: self.x * rhs,
y: self.y * rhs,
z: self.z * rhs,
}
}
}

我们有where子句，因为我们的泛型T也需要实现特性Mul和Copy。CCD_ 12，因为我们需要复制CCD_。

您的点产品实施也需要根据进行更改

impl<T> Mul<&Point3D<T>> for &Point3D<T> 
where T: Mul<Output=T> + Add<Output=T> + Copy
{
type Output = T;
fn mul(self, rhs: &Point3D<T>) -> Self::Output {
self.x * rhs.x + self.y * rhs.y + self.z * rhs.z
}
}

使用Add，因为我们当然需要能够在这里添加泛型T。