Method close

src/main/java/org/jpl7/Query.java:616–650

This method can be used to close an open query before its solutions are exhausted. It is called automatically when solutions are exhausted. Calling close() on an already closed Query has no effect. Here is one way to get the first three solutions to a Query: Query q = new Query(predicate

()

	 * </pre>
	 */
	public final void close() {
		if (!open) {
			return; // it is not an error to attempt to close a closed Query
		}
		if (Prolog.thread_self() == -1) {
			throw new JPLException("no engine is attached to this thread");
		}
		if (Prolog.current_engine().value != engine.value) {
			throw new JPLException("this Query's engine is not that which is attached to this thread");
		}
		qid_t topmost = Prolog.current_query();
		if (topmost.value != this.qid.value) {
			throw new JPLException("this Query (" + this.hashCode() + ":" + this.toString() + ") is not topmost ("
					+ topmost.hashCode() + ":" + topmost.toString() + ") within its engine[" + engine.value + "]");
		}
		Prolog.close_query(qid);
		qid = null; // for tidiness
		org.jpl7.fli.Prolog.discard_foreign_frame(fid);
		fid = null; // for tidiness
		if (Prolog.current_query() == null) { // only Query open in this engine?
			if (Prolog.current_engine_is_pool()) { // this (Query's) engine is
													// from the pool?
				Prolog.release_pool_engine();
				// System.out.println("JPL releasing engine[" + engine.value +
				// "]");
			} else {
				// System.out.println("JPL leaving engine[" + engine.value +
				// "]");
			}
		} else {
			// System.out.println("JPL retaining engine[" + engine.value + "]
		}
		open = false; // this Query is now closed
		engine = null; // this Query, being closed, is no longer associated with any Prolog engine
    }

	/**
	 * calls the Query's goal to exhaustion and returns an array of zero or more