pub trait MulDiv<RHS = Self> {
type Output;
// Required methods
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>;
}Expand description
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.
Required Associated Types§
type Output
type Output
Output type for the methods of this trait.
Required Methods§
fn mul_div_floor(self, num: RHS, denom: RHS) -> Option<Self::Output>
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>
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>
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);