Enum formality_core::variable::CoreVariable

pub enum CoreVariable<L: Language> {
    UniversalVar(CoreUniversalVar<L>),
    ExistentialVar(CoreExistentialVar<L>),
    BoundVar(CoreBoundVar<L>),
}

A term representing a variable.

Variants

UniversalVar(CoreUniversalVar<L>)

A “universal free variable” is a variable that appears free in all terms because it is bound in the environment. Universal means that it arose from a “forall” binder. Universal variables are a kind of placeholder meant to represent “some value” about which you know nothing except what you are told to assume.

ExistentialVar(CoreExistentialVar<L>)

An “existential free variable” is a variable that appears free in all terms because it is bound in the environment. Existential means that it arose from a “exists” binder. Existential variables are a kind of placeholder for which you will eventually find some specific value, so the rules typically accumulate constraints.

BoundVar(CoreBoundVar<L>)

A bound variable is one that is bound by some enclosing Binder in this term (or a binder about to be constructex; see fresh_bound_var).

Implementations

impl<L: Language> CoreVariable<L>

pub fn kind(&self) -> CoreKind<L>

pub fn shift_in(&self) -> Self

Shift a variable in through binders binding levels. Only affects bound variables.

pub fn shift_out(&self) -> Option<Self>

Shift a variable out through binders binding levels. Only affects bound variables. Returns None if the variable is bound within those binding levels.

pub fn is_free(&self) -> bool

A variable is free (i.e., not bound by any internal binder) if it is an existential variable, a universal, or has a debruijn index of None. The latter occurs when you open a binder (and before you close it back up again).

pub fn is_universal(&self) -> bool

Trait Implementations

impl<L: Clone + Language> Clone for CoreVariable<L>

fn clone(&self) -> CoreVariable<L>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<L: Language> CoreVisit<L> for CoreVariable<L>

fn free_variables(&self) -> Vec<CoreVariable<L>>

Extract the list of free variables (for the purposes of this function, defined by Variable::is_free). The list may contain duplicates and must be in a determinstic order (though the order itself isn’t important).

fn size(&self) -> usize

Measures the overall size of the term by counting constructors etc. Used to determine overflow.

fn assert_valid(&self)

Asserts various validity constraints and panics if they are not held. These validition constraints should never fail unless there is a bug in our logic. This is to aid with fuzzing and bug detection.

fn references_only_universal_variables(&self) -> bool

True if this term references only universal variables. This means that it contains no existential variables. If this is a goal, then when we prove it true, we don’t expect any substitution. This is similar, but not identical, to the commonly used term “ground term”, which in Prolog refers to a term that contains no variables. The difference here is that the term may contain variables, but only those instantiated universally (∀).

impl<L: Language> Debug for CoreVariable<L>

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

Formats the value using the given formatter.

impl<L: Language> DowncastTo<CoreBoundVar<L>> for CoreVariable<L>

fn downcast_to(&self) -> Option<CoreBoundVar<L>>

impl<L: Language> DowncastTo<CoreExistentialVar<L>> for CoreVariable<L>

fn downcast_to(&self) -> Option<CoreExistentialVar<L>>

impl<L: Language> DowncastTo<CoreUniversalVar<L>> for CoreVariable<L>

fn downcast_to(&self) -> Option<CoreUniversalVar<L>>

impl<L: Language> DowncastTo<CoreVariable<L>> for CoreVariable<L>

fn downcast_to(&self) -> Option<CoreVariable<L>>

impl<L: Hash + Language> Hash for CoreVariable<L>

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<L: Language> Index<CoreVariable<L>> for CoreSubstitution<L>

type Output = <L as Language>::Parameter

The returned type after indexing.

fn index(&self, index: CoreVariable<L>) -> &Self::Output

Performs the indexing (container[index]) operation.

impl<L: Ord + Language> Ord for CoreVariable<L>

fn cmp(&self, other: &CoreVariable<L>) -> 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<L: PartialEq + Language> PartialEq for CoreVariable<L>

fn eq(&self, other: &CoreVariable<L>) -> 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<L: PartialOrd + Language> PartialOrd for CoreVariable<L>

fn partial_cmp(&self, other: &CoreVariable<L>) -> 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<L: Language> UpcastFrom<CoreBoundVar<L>> for CoreVariable<L>

fn upcast_from(v: CoreBoundVar<L>) -> CoreVariable<L>

impl<L: Language> UpcastFrom<CoreExistentialVar<L>> for CoreVariable<L>

fn upcast_from(v: CoreExistentialVar<L>) -> CoreVariable<L>

impl<L: Language> UpcastFrom<CoreUniversalVar<L>> for CoreVariable<L>

fn upcast_from(v: CoreUniversalVar<L>) -> CoreVariable<L>

impl<L: Language> UpcastFrom<CoreVariable<L>> for CoreVariable<L>

fn upcast_from(v: CoreVariable<L>) -> CoreVariable<L>

impl<L: Copy + Language> Copy for CoreVariable<L>

impl<L: Eq + Language> Eq for CoreVariable<L>

impl<L: Language> StructuralEq for CoreVariable<L>

impl<L: Language> StructuralPartialEq for CoreVariable<L>