Struct reciprocal::PartialReciprocal

pub struct PartialReciprocal { /* fields omitted */ }

A PartialReciprocal represents an integer (floored) division by a u64 that’s not 0, 1 or u64::MAX.

Once constructed for a given d, applying a PartialReciprocal to a u64 computes an integer division of that argument by d. The parameters represent an expression of the form f(x) = (x + increment) * multiplier >> (64 + shift) in full 128-bit arithmetic; for appropriately chosen values, this expression can implement any (unsigned) integer division.

Implementations

impl PartialReciprocal

pub fn new(d: u64) -> Option<PartialReciprocal>

Constructs a PartialReciprocal that computes a floored division by d.

Returns None if d == 0, or if d == 1 || d == u64::MAX: these last two divisors cannot be safely implemented as PartialReciprocal (the sequence would fail for u64::MAX / 1 and u64::MAX / u64::MAX).

The full Reciprocal handles these last two cases, at the expense of one more u64 field and a branch.

#[must_use]

pub fn apply(self, x: u64) -> u64

Computes x / d, where d is the divison for which this reciprocal was constructed.

The library tries to dispatch to a reasonable implementation for each platform.

#[must_use]

pub fn apply_saturating(self, x: u64) -> u64

Computes x / d with saturating arithmetic.

#[must_use]

pub fn apply_overflowing(self, x: u64) -> u64

Computes x / d with an alternative saturating increment that is shorter and equally efficient on x86-64.

Trait Implementations

impl Clone for PartialReciprocal

fn clone(&self) -> PartialReciprocal

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PartialReciprocal

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for PartialReciprocal

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl PartialEq<PartialReciprocal> for PartialReciprocal

fn eq(&self, other: &PartialReciprocal) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &PartialReciprocal) -> bool

This method tests for !=.

impl Copy for PartialReciprocal

impl Eq for PartialReciprocal

impl StructuralEq for PartialReciprocal

impl StructuralPartialEq for PartialReciprocal