Synchronous callback-style solver. The main public entry point of yopl.

import solve from 'yopl';
// or: import solve from 'yopl/solve.js';

solve(rules, name, args, callback): void

The callback receives the live unification environment. Use assemble(variable, env) from deep6/traverse/assemble.js to extract bound values.

import {variable} from 'deep6/env.js';
import assemble from 'deep6/traverse/assemble.js';
import solve from 'yopl';
const rules = {
 one: () => [{args: [1]}]
};
const X = variable('X');
solve(rules, 'one', [X], env => {
 console.log(assemble(X, env)); // 1
});

A rule is a function (or array of functions for a disjunction) that receives a fresh batch of logical variables and returns an array of terms. The first term is the rule head ({args: [...]}); the rest are body goals.

const rules = {
 member: [(V, X) => [{args: [{value: V, next: X}, V]}], (V, X) => [{args: [{next: X}, V]}, {name: 'member', args: [X, V]}]]
};

A body goal can be:

• a structured term: {name: 'member', args: [X, V]}
• a bare string (rule name with no args): 'true'
• an inline JS function (env, goals, stack) => boolean | GoalFrame for predicates implemented directly in JavaScript.

See rules-system for helpers (head, term, list, cut, call, ...) that build these shapes ergonomically.