Rust Div用法及代码示例

use std::ops::Div;

// By the fundamental theorem of arithmetic, rational numbers in lowest
// terms are unique. So, by keeping `Rational`s in reduced form, we can
// derive `Eq` and `PartialEq`.
#[derive(Debug, Eq, PartialEq)]
struct Rational {
    numerator: usize,
    denominator: usize,
}

impl Rational {
    fn new(numerator: usize, denominator: usize) -> Self {
        if denominator == 0 {
            panic!("Zero is an invalid denominator!");
        }

        // Reduce to lowest terms by dividing by the greatest common
        // divisor.
        let gcd = gcd(numerator, denominator);
        Self {
            numerator: numerator / gcd,
            denominator: denominator / gcd,
        }
    }
}

impl Div for Rational {
    // The division of rational numbers is a closed operation.
    type Output = Self;

    fn div(self, rhs: Self) -> Self::Output {
        if rhs.numerator == 0 {
            panic!("Cannot divide by zero-valued `Rational`!");
        }

        let numerator = self.numerator * rhs.denominator;
        let denominator = self.denominator * rhs.numerator;
        Self::new(numerator, denominator)
    }
}

// Euclid's two-thousand-year-old algorithm for finding the greatest common
// divisor.
fn gcd(x: usize, y: usize) -> usize {
    let mut x = x;
    let mut y = y;
    while y != 0 {
        let t = y;
        y = x % y;
        x = t;
    }
    x
}

assert_eq!(Rational::new(1, 2), Rational::new(2, 4));
assert_eq!(Rational::new(1, 2) / Rational::new(3, 4),
           Rational::new(2, 3));

use std::ops::Div;

struct Scalar { value: f32 }

#[derive(Debug, PartialEq)]
struct Vector { value: Vec<f32> }

impl Div<Scalar> for Vector {
    type Output = Self;

    fn div(self, rhs: Scalar) -> Self::Output {
        Self { value: self.value.iter().map(|v| v / rhs.value).collect() }
    }
}

let scalar = Scalar { value: 2f32 };
let vector = Vector { value: vec![2f32, 4f32, 6f32] };
assert_eq!(vector / scalar, Vector { value: vec![1f32, 2f32, 3f32] });