Struct Clause 

pub struct Clause {
    pub id: ClauseId,
    pub head: Expr,
    pub body: Vec<Expr>,
    pub source: Option<Origin>,
}

A parsed logic clause: a head goal plus an optional list of body goals.

A clause with an empty body is a fact; one with body goals is a rule.

Fields

id: ClauseId

Identifier of this clause within its database.

head: Expr

The head goal (the conclusion the clause proves).

body: Vec<Expr>

Body goals that must all hold for the head to hold; empty for a fact.

source: Option<Origin>

Source origin of the clause, when known.

Implementations

impl Clause

pub fn predicate(&self) -> Result<Symbol>

Returns the predicate symbol of the clause head.

pub fn arity(&self) -> Result<usize>

Returns the arity (argument count) of the clause head.

pub fn fact_expr(&self) -> Expr

Renders the clause back to its canonical (fact ...) or (rule ...) surface expression.

Trait Implementations

impl Clone for Clause

fn clone(&self) -> Clause

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Clause

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

Formats the value using the given formatter.

impl Eq for Clause

impl PartialEq for Clause

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

Tests for self and other values to be equal, and is used by ==.

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

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

impl StructuralPartialEq for Clause