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 Clone for Present

fn clone(&self) -> Present

Returns a copy of the value.

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

Performs copy-assignment from source.

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 Hash for Present

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, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T: Clone> Multiply<T> for Present

type Output = T

Output type per the Mul trait.

fn multiply(self, rhs: &T) -> T

Core method per the Mul trait.

impl Ord for Present

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

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for Present

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

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

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

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Present

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

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

fn lt(&self, other: &Rhs) -> bool

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

fn le(&self, other: &Rhs) -> bool

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

fn gt(&self, other: &Rhs) -> bool

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

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 plus_equals(&mut self, _rhs: &Self)

The method of std::ops::AddAssign, for types that do not implement AddAssign.

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 Copy for Present

impl Eq for Present

impl StructuralPartialEq for Present