Struct Rule

pub struct Rule {
    pub head: Unifiable,
    pub body: Goal,
}

Defines a fact or rule.

A rule consists of a head and a body. The head must be a complex term, and the body is a goal.
For facts, the body is set to Nil.

Fields

head: Unifiable

body: Goal

Implementations

impl Rule

pub fn key(&self) -> String

Creates a key (predicate name) for indexing into the knowledge base.

The name of a predicate consists of its functor and its arity, separated by a slash. For example, for the fact loves(Chandler, Monica), the functor is loves and the arity is 2, therefore the name of the predicate is loves/2.

Arguments

• self

Return

• key - String

Usage

use suiron::*;

let query = parse_query("parse($In, $Out, $ErrIn, $ErrOut)");
match query {
    Ok(q) => { println!("{}", q.key()); },
    Err(msg) => { println!("{}", msg); },
}
// Prints: parse/4

pub fn get_head(&self) -> Unifiable

Returns the head of this rule.

Arguments

• self

Return

• head term - (SComplex)

use suiron::*;

clear_id();
let kb = test_kb();
// Get grandfather rule.
let rule = get_rule(&kb, "grandfather/2", 0);
let head = rule.get_head();
println!("{}", head); // Prints: grandfather($X_1, $Y_2)

pub fn get_body(&self) -> Goal

Returns the body of this rule, which is a goal.

Arguments

• self

Return

• body - (Goal)

Usage

use suiron::*;

clear_id();
let kb = test_kb();
// Get grandfather rule.
let rule = get_rule(&kb, "grandfather/2", 0);
let body = rule.get_body();
println!("{}", body);  // father($X_1, $Z_3), father($Z_3, $Y_2)

pub fn recreate_variables(self, recreated_vars: &mut VarMap) -> Rule

The scope of a logic variable is the rule or goal in which it is defined.

When the inference algorithm tries to solve a goal, it calls this method to ensure that the variables are unique.

Argument

• self
• recreated_vars - logic variables already recreated

Return

• Rule

Usage

use suiron::*;

clear_id();
match parse_rule("parent($X, $Y) :- mother($X, $Y).") {
    Ok(rule) => {
        let mut var_map = VarMap::new();
        let rule = rule.recreate_variables(&mut var_map);
        println!("{}", rule);
    },
    Err(msg) => { println!("{}", msg); },
}
// Prints: parent($X_1, $Y_2) :- mother($X_1, $Y_2).

Trait Implementations

impl Clone for Rule

fn clone(&self) -> Rule

Returns a duplicate of the value.

const 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 Display for Rule

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

Formats the value using the given formatter.