Struct Rule 

pub struct Rule {
    pub head: Atom,
    pub body: Vec<Literal>,
}

Datalog rule: head :- body_1, ..., body_n.

Fields

head: Atom

Head atom.

body: Vec<Literal>

Body literals. An empty body represents a fact.

Implementations

impl Rule

pub fn positive(head: Atom, body: Vec<Atom>) -> Self

Construct a rule whose body contains only positive literals.

Convenience for the common case — callers that do not need negation never have to name Literal.

pub fn new(head: Atom, body: Vec<Literal>) -> Self

Construct a rule with an explicit literal body.

pub fn is_safe(&self) -> bool

Returns true when the rule satisfies Datalog¬ safety.

A rule is safe when:

1. Every variable appearing in the head is bound by some positive body atom or Bind.
2. Every variable appearing in a negative body literal is bound by some positive body atom or Bind (range restriction — negation-as-failure requires the negated atom to be ground by the time it is evaluated).
3. Every variable appearing inside a Literal::Filter is bound by some positive body atom or Bind — filters guard candidate bindings, they do not produce them.
4. Every variable inside a Literal::Bind expression is bound by an earlier positive body atom or Bind, and the Bind’s output variable is fresh (not bound by any earlier positive atom or Bind).

Trait Implementations

impl Clone for Rule

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Rule

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

Formats the value using the given formatter.

impl Eq for Rule

impl Hash for Rule

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 PartialEq for Rule

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Rule