# Struct chalk_engine::Minimums

``````pub(crate) struct Minimums {
pub(crate) positive: TimeStamp,
pub(crate) negative: TimeStamp,
}``````
Expand description

The `Minimums` structure is used to track the dependencies between some item E on the evaluation stack. In particular, it tracks cases where the success of E depends (or may depend) on items deeper in the stack than E (i.e., with lower DFNs).

`positive` tracks the lowest index on the stack to which we had a POSITIVE dependency (e.g. `foo(X) :- bar(X)`) – meaning that in order for E to succeed, the dependency must succeed. It is initialized with the index of the predicate on the stack. So imagine we have a stack like this:

``````    // 0 foo(X)   <-- bottom of stack
// 1 bar(X)
// 2 baz(X)   <-- top of stack
``````

In this case, `positive` would be initially 0, 1, and 2 for `foo`, `bar`, and `baz` respectively. This reflects the fact that the answers for `foo(X)` depend on the answers for `foo(X)`. =)

Now imagine that we had a clause `baz(X) :- foo(X)`, inducing a cycle. In this case, we would update `positive` for `baz(X)` to be 0, reflecting the fact that its answers depend on the answers for `foo(X)`. Similarly, the minimum for `bar` would (eventually) be updated, since it too transitively depends on `foo`. `foo` is unaffected.

`negative` tracks the lowest index on the stack to which we had a NEGATIVE dependency (e.g., `foo(X) :- not { bar(X) }`) – meaning that for E to succeed, the dependency must fail. This is initially `usize::MAX`, reflecting the fact that the answers for `foo(X)` do not depend on `not(foo(X))`. When negative cycles are encountered, however, this value must be updated.

## Fields§

§`positive: TimeStamp`§`negative: TimeStamp`

## Implementations§

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### impl Minimums

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#### pub(crate) fn take_minimums(&mut self, other: &Minimums)

Update our fields to be the minimum of our current value and the values from other.

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## Trait Implementations§

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### impl Clone for Minimums

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#### fn clone(&self) -> Minimums

Returns a copy of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl Debug for Minimums

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

Formats the value using the given formatter. Read more
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## Blanket Implementations§

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### impl<T> Any for Twhere T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for Twhere T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for Twhere T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> Cast for T

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#### fn cast<U>(self, interner: <U as HasInterner>::Interner) -> Uwhere Self: CastTo<U>, U: HasInterner,

Cast a value to type `U` using `CastTo`.
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T> Instrument for T

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#### fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided [`Span`], returning an `Instrumented` wrapper. Read more
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#### fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more
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### impl<T, U> Into<U> for Twhere U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for Twhere T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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### impl<T> WithSubscriber for T

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#### fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>where S: Into<Dispatch>,

Attaches the provided `Subscriber` to this type, returning a [`WithDispatch`] wrapper. Read more
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#### fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default `Subscriber` to this type, returning a [`WithDispatch`] wrapper. Read more