Trait std::ops::Mul1.0.0 [−] [src]

#[lang = "mul"]

pub trait Mul<RHS = Self> {
    type Output;
    fn mul(self, rhs: RHS) -> Self::Output;
}

The multiplication operator *.

Note that RHS is Self by default, but this is not mandatory.

Examples

Multipliable rational numbers

use std::ops::Mul;

// 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 {
    nominator: usize,
    denominator: usize,
}

impl Rational {
    fn new(nominator: 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(nominator, denominator);
        Rational {
            nominator: nominator / gcd,
            denominator: denominator / gcd,
        }
    }
}

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

    fn mul(self, rhs: Self) -> Self {
        let nominator = self.nominator * rhs.nominator;
        let denominator = self.denominator * rhs.denominator;
        Rational::new(nominator, 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(2, 3) * Rational::new(3, 4),
           Rational::new(1, 2));Run

Multiplying vectors by scalars as in linear algebra

use std::ops::Mul;

struct Scalar { value: usize }

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

impl Mul<Scalar> for Vector {
    type Output = Vector;

    fn mul(self, rhs: Scalar) -> Vector {
        Vector { value: self.value.iter().map(|v| v * rhs.value).collect() }
    }
}

let vector = Vector { value: vec![2, 4, 6] };
let scalar = Scalar { value: 3 };
assert_eq!(vector * scalar, Vector { value: vec![6, 12, 18] });Run

Associated Types

The resulting type after applying the * operator.

Required Methods

Performs the * operation.

Implementors