rust - `method ` sub ` has an incompatible type for trait`(可以为不同的结构实现sub吗？)

Question

我正在尝试编写2个结构Point和Bound，以便您可以从Point中减去Bound。

代码:

struct Point {
    x:usize,
    y:usize,
}
impl Sub for Point {
    type Output = Point;
    fn sub(self,other:Point) -> Point {
        Point { x:self.x-other.x, y:self.y-other.y }
    }
}
struct Bound { min:Point,max:Point }
impl Sub for Bound {
    type Output = Bound;
    fn sub(self,other:Point) -> Bound {
        Bound { min:self.min-other, max:self.max-other }
    }
}

我得到了错误:

method `sub` has an incompatible type for trait

expected struct `construct::Bound`, found struct `construct::Point`

note: expected fn pointer `fn(construct::Bound, construct::Bound) -> construct::Bound`
         found fn pointer `fn(construct::Bound, construct::Point) -> construct::Bound`rustc(E0053)
main.rs(565, 9): expected struct `construct::Bound`, found struct `construct::Point`

我在这里尝试的方式可能吗？最好的方法是什么？

Answer 1

Sub有一个参数Rhs，默认为Self。 impl Sub for Bound是impl Sub<Bound> for Bound的缩写。您可能要添加impl Sub<Point> for Bound。

impl Sub<Point> for Bound {
    type Output = Bound;
    fn sub(self, other: Point) -> Bound {
        Bound { min:self.min - other, max:self.max - other }
    }
}

注意:这并不完全有效，因为当前 impl Sub for Point实际上使用第一个 other消耗了 -，而第二个 -保留了“使用移动值”。最简单的方法可能只是将 #[derive(Clone, Copy)]放在 Point上。