Struct differential_dataflow::difference::Present

pub struct Present;

A zero-sized difference that indicates the presence of a record.

This difference type has no negation, and present records cannot be retracted. Addition and multiplication maintain presence, and zero does not inhabit the type.

The primary feature of this type is that it has zero size, which reduces the overhead of differential dataflow’s representations for settings where collections either do not change, or for which records are only added (for example, derived facts in Datalog).

Trait Implementations

impl Abomonation for Present

unsafe fn entomb<W: Write>(&self, _write: &mut W) -> Result<()>

Write any additional information about &self beyond its binary representation.

fn extent(&self) -> usize

Reports the number of further bytes required to entomb self.

unsafe fn exhume<'a, 'b>(
    &'a mut self,
    bytes: &'b mut [u8]
) -> Option<&'b mut [u8]>

Recover any information for &mut self not evident from its binary representation.

impl<'a> AddAssign<&'a Present> for Present

fn add_assign(&mut self, _rhs: &'a Self)

Performs the += operation.

impl Clone for Present

fn clone(&self) -> Present

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for Present

impl Debug for Present

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Present

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error> where
    __D: Deserializer<'de>, 

Deserialize this value from the given Serde deserializer.

impl Eq for Present

impl Hash for Present

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

Feeds this value into the given Hasher.

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

Feeds a slice of this type into the given Hasher.

impl<T> Mul<T> for Present

type Output = T

The resulting type after applying the * operator.

fn mul(self, rhs: T) -> T

Performs the * operation.

impl Ord for Present

fn cmp(&self, other: &Present) -> Ordering

This method returns an Ordering between self and other.

#[must_use]pub fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]pub fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]pub fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl PartialEq<Present> for Present

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

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

#[must_use]pub fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialOrd<Present> for Present

fn partial_cmp(&self, other: &Present) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use]pub fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use]pub fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use]pub fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use]pub fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Semigroup for Present

fn is_zero(&self) -> bool

Returns true if the element is the additive identity.

impl Serialize for Present

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error> where
    __S: Serializer, 

Serialize this value into the given Serde serializer.

impl StructuralEq for Present

impl StructuralPartialEq for Present