[−][src]Trait muldiv::MulDiv

pub trait MulDiv<RHS = Self> {
    type Output;
    fn mul_div_floor(self, num: RHS, denom: RHS) -> Option<Self::Output>;

    fn mul_div_round(self, num: RHS, denom: RHS) -> Option<Self::Output>;

    fn mul_div_ceil(self, num: RHS, denom: RHS) -> Option<Self::Output>;
}

Trait for calculating val * num / denom with different rounding modes and overflow protection.

Implementations of this trait have to ensure that even if the result of the multiplication does not fit into the type, as long as it would fit after the division the correct result has to be returned instead of None. None only should be returned if the overall result does not fit into the type.

This specifically means that e.g. the u64 implementation must, depending on the arguments, be able to do 128 bit integer multiplication.

Associated Types

type Output

Output type for the methods of this trait.

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Required methods

fn mul_div_floor(self, num: RHS, denom: RHS) -> Option<Self::Output>

Calculates floor(val * num / denom), i.e. the largest integer less than or equal to the result of the division.

Example

extern crate muldiv;
use muldiv::MulDiv;

let x = 3i8.mul_div_floor(4, 2);
assert_eq!(x, Some(6));

let x = 5i8.mul_div_floor(2, 3);
assert_eq!(x, Some(3));

let x = (-5i8).mul_div_floor(2, 3);
assert_eq!(x, Some(-4));

let x = 3i8.mul_div_floor(3, 2);
assert_eq!(x, Some(4));

let x = (-3i8).mul_div_floor(3, 2);
assert_eq!(x, Some(-5));

let x = 127i8.mul_div_floor(4, 3);
assert_eq!(x, None);

fn mul_div_round(self, num: RHS, denom: RHS) -> Option<Self::Output>

Calculates round(val * num / denom), i.e. the closest integer to the result of the division. If both surrounding integers are the same distance (x.5), the one with the bigger absolute value is returned (round away from 0.0).

Example

extern crate muldiv;
use muldiv::MulDiv;

let x = 3i8.mul_div_round(4, 2);
assert_eq!(x, Some(6));

let x = 5i8.mul_div_round(2, 3);
assert_eq!(x, Some(3));

let x = (-5i8).mul_div_round(2, 3);
assert_eq!(x, Some(-3));

let x = 3i8.mul_div_round(3, 2);
assert_eq!(x, Some(5));

let x = (-3i8).mul_div_round(3, 2);
assert_eq!(x, Some(-5));

let x = 127i8.mul_div_round(4, 3);
assert_eq!(x, None);

fn mul_div_ceil(self, num: RHS, denom: RHS) -> Option<Self::Output>

Calculates ceil(val * num / denom), i.e. the the smallest integer greater than or equal to the result of the division.

Example

extern crate muldiv;
use muldiv::MulDiv;

let x = 3i8.mul_div_ceil(4, 2);
assert_eq!(x, Some(6));

let x = 5i8.mul_div_ceil(2, 3);
assert_eq!(x, Some(4));

let x = (-5i8).mul_div_ceil(2, 3);
assert_eq!(x, Some(-3));

let x = 3i8.mul_div_ceil(3, 2);
assert_eq!(x, Some(5));

let x = (-3i8).mul_div_ceil(3, 2);
assert_eq!(x, Some(-4));

let x = (127i8).mul_div_ceil(4, 3);
assert_eq!(x, None);
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Implementors

impl MulDiv<i16> for i16[src]

type Output = i16

impl MulDiv<i32> for i32[src]

type Output = i32

impl MulDiv<i64> for i64[src]

type Output = i64

impl MulDiv<i8> for i8[src]

type Output = i8

impl MulDiv<u16> for u16[src]

type Output = u16

impl MulDiv<u32> for u32[src]

type Output = u32

impl MulDiv<u64> for u64[src]

type Output = u64

impl MulDiv<u8> for u8[src]

type Output = u8

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