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Frac

vstd::resource::frac_opt

Struct Frac 

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pub struct Frac<T> { /* private fields */ }
Expand description

Token that maintains fractional access to some resource. This allows multiple clients to obtain shared references to some resource via borrow.

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impl<T> Frac<T>

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pub closed spec fn id(self) -> Loc

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pub closed spec fn resource(self) -> T

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pub closed spec fn frac(self) -> real

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pub open spec fn valid(self, id: Loc, frac: real) -> bool

{
    &&& self.id() == id
    &&& self.frac() == frac

}
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pub proof fn new(tracked v: T) -> tracked result : Self

ensures
result.frac() == 1 as real,
result.resource() == v,

Create a fractional token that maintains shared access to the input resource.

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pub proof fn agree(tracked &self, tracked other: &Self)

requires
self.id() == other.id(),
ensures
self.resource() == other.resource(),

Two tokens agree on values of the underlying resource.

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pub proof fn split_to(tracked &mut self, result_frac: real) -> tracked result : Self

requires
(0 as real) < result_frac < old(self).frac(),
ensures
self.id() == old(self).id(),
result.id() == old(self).id(),
self.resource() == old(self).resource(),
result.resource() == old(self).resource(),
self.frac() == old(self).frac() - result_frac,
result.frac() == result_frac,

Split one resource into two resources whose quantities sum to the original. The returned token has quantity result_frac; the new value of the input token has quantity old(self).frac() - result_frac.

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pub proof fn split(tracked &mut self) -> tracked result : Self

ensures
self.id() == old(self).id(),
result.id() == old(self).id(),
self.resource() == old(self).resource(),
result.resource() == old(self).resource(),
self.frac() == old(self).frac() / 2 as real,
result.frac() == old(self).frac() / 2 as real,

Split one resource by half into two resources whose quantities sum to the original. The returned token has quantity n; the new value of the input token has quantity old(self).frac() - n.

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pub proof fn combine(tracked &mut self, tracked other: Self)

requires
old(self).id() == other.id(),
ensures
self.id() == old(self).id(),
self.resource() == old(self).resource(),
self.resource() == other.resource(),
self.frac() == old(self).frac() + other.frac(),

Combine two tokens, summing their quantities.

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pub proof fn bounded(tracked &self)

ensures
(0 as real) < self.frac() <= (1 as real),

Allowed values for a token’s quantity.

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pub proof fn borrow(tracked &self) -> tracked ret : &T

ensures
ret == self.resource(),

Obtain shared access to the underlying resource.

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pub proof fn take_resource(tracked self) -> tracked pair : (T, Empty<T>)

requires
self.frac() == 1 as real,
ensures
pair.0 == self.resource(),
pair.1.id() == self.id(),

Reclaim full ownership of the underlying resource.

Auto Trait Implementations§

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impl<T> Freeze for Frac<T>

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impl<T> RefUnwindSafe for Frac<T>
where T: RefUnwindSafe,

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impl<T> Send for Frac<T>
where T: Send + Sync,

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impl<T> Sync for Frac<T>
where T: Sync + Send,

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impl<T> Unpin for Frac<T>
where T: Unpin,

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impl<T> UnsafeUnpin for Frac<T>

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impl<T> UnwindSafe for Frac<T>
where T: UnwindSafe,

Blanket Implementations§

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impl<T> Any for T
where 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 T
where 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 T
where 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> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, VERUS_SPEC__A> FromSpec<T> for VERUS_SPEC__A
where VERUS_SPEC__A: From<T>,

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exec fn obeys_from_spec() -> bool

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exec fn from_spec(v: T) -> VERUS_SPEC__A

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impl<T, U> Into<U> for T
where 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, VERUS_SPEC__A> IntoSpec<T> for VERUS_SPEC__A
where VERUS_SPEC__A: Into<T>,

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exec fn obeys_into_spec() -> bool

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exec fn into_spec(self) -> T

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impl<T, U> IntoSpecImpl<U> for T
where U: From<T>,

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open spec fn obeys_into_spec() -> bool

{ <U as FromSpec<Self>>::obeys_from_spec() }
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open spec fn into_spec(self) -> U

{ U::from_spec(self) }
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impl<T, U> TryFrom<U> for T
where 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, VERUS_SPEC__A> TryFromSpec<T> for VERUS_SPEC__A
where VERUS_SPEC__A: TryFrom<T>,

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exec fn obeys_try_from_spec() -> bool

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exec fn try_from_spec( v: T, ) -> Result<VERUS_SPEC__A, <VERUS_SPEC__A as TryFrom<T>>::Error>

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impl<T, U> TryInto<U> for T
where 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, VERUS_SPEC__A> TryIntoSpec<T> for VERUS_SPEC__A
where VERUS_SPEC__A: TryInto<T>,

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exec fn obeys_try_into_spec() -> bool

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exec fn try_into_spec(self) -> Result<T, <VERUS_SPEC__A as TryInto<T>>::Error>

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impl<T, U> TryIntoSpecImpl<U> for T
where U: TryFrom<T>,

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open spec fn obeys_try_into_spec() -> bool

{ <U as TryFromSpec<Self>>::obeys_try_from_spec() }
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open spec fn try_into_spec(self) -> Result<U, <U as TryFrom<T>>::Error>

{ <U as TryFromSpec<Self>>::try_from_spec(self) }