Tau-Prolog : enhancing sample

// Create a Prolog session let program = ` parent(john, mary). parent(susan, mary). parent(mary, alice). parent(mary, bob). parent(paul, bob). grandparent(X, Y) :- parent(X, Z), parent(Z, Y). sibling(X, Y) :- parent(Z, X), parent(Z, Y), X \\= Y. ancestor(X, Y) :- parent(X, Y). ancestor(X, Y) :- parent(X, Z), ancestor(Z, Y). `; function showAnswer(answer, context) { if (pl.type.is_substitution(answer)) { for (let key in answer.links) { document.write(answer.links[key].id + "<br>"); // Extract only the name } } else { console.log("no answer"); } } class PrologSession { constructor() { this.session = pl.create(1000); this.consultationDone = false; this.consultationResolve = null; // Load Prolog program this.session.consult(program, { success: () => { this.consultationDone = true; if (this.consultationResolve) { this.consultationResolve(); // ✅ Resolves any pending queries this.consultationResolve = null; // Prevents multiple calls } }, error: (err) => { console.error("Prolog consultation error:", err); } }); } waitForConsultation() { return new Promise((resolve) => { if (this.consultationDone) { resolve(); // If already done, resolve immediately } else { this.consultationResolve = resolve; // Store resolve function } }); } query(queryString, context) { document.write(context + "<br />"); this.waitForConsultation().then(() => { this.session.query(queryString, { success: () => { this.session.answers((a) => showAnswer(a, context)); }, error: (err) => { console.error("Query error:", err); } }); }); } } // Example usage const prolog = new PrologSession(); prolog.query("ancestor(X, bob).", "Ancestors of Bob are: ");