31ff28d3ee
git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1936 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
870 lines
37 KiB
Java
870 lines
37 KiB
Java
//tabstop=4
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//*****************************************************************************/
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// Project: jpl
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//
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// File: $Id: Query.java,v 1.2 2007-09-27 15:25:32 vsc Exp $
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// Date: $Date: 2007-09-27 15:25:32 $
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// Author: Fred Dushin <fadushin@syr.edu>
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//
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//
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// Description:
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//
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//
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// -------------------------------------------------------------------------
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// Copyright (c) 2004 Paul Singleton
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// Copyright (c) 1998 Fred Dushin
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// All rights reserved.
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Library Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Library Public License for more details.
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//*****************************************************************************/
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package jpl;
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import java.util.Enumeration;
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import java.util.Hashtable;
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import java.util.Map;
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import java.util.Vector;
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import jpl.fli.*;
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//----------------------------------------------------------------------/
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// Query
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/**
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* A Query instance is created by an application in order to query the Prolog database
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* (or to invoke a built-in predicate).
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* It is initialised with a
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* Compound (or Atom) denoting the goal which is to be called, and also contains assorted private state
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* relating to solutions. In some future version, it may contain details of the module
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* in which the goal is to be called.<p>
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* A Query is either open or closed: when closed, it has no connection to the Prolog system;
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* when open, it is linked to an active goal within a Prolog engine.<p>
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* The Query class implements the Enumeration interface,
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* through which one can obtain successive solutions. The Enumeration
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* hasMoreElements() method returns true if the call or redo succeeded (otherwise
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* false), and if the call or redo did succeed, the nextElement() method returns
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* a Hashtable representing variable bindings; the elements in the
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* Hashtable are Terms, indexed by the (String) names of the Variables with which they are associated.
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* For example, if <i>p(a)</i> and <i>p(b)</i> are facts in the Prolog
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* database, then the following is equivalent to printing all
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* the solutions to the Prolog query <i>p(X)</i>:
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* <pre>
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* Variable X = new Variable("X");
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* Term arg[] = { X };
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* Query q = new Query("p", arg);
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*
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* while (q.hasMoreElements()){
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* Term bound_to_x = ((Hashtable) q.nextElement()).get("X");
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* System.out.println(bound_to_x);
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* }
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* </pre>
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* Make sure to close the Query (using the close() method) if you do not need
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* any further solutions which it may have.
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* It is safe (although redundant) to close a Query whose solutions are already exhausted,
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* or which is already closed.
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*
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* To obtain just one solution from a Query, use the oneSolution() method.
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*
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* To obtain all solutions, use the allSolutions() method.
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*
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* To obtain at most N solutions, use the nSolutions() method.
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*
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* To determine merely whether the Query is provable,
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* use the hasSolution() method
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* (i.e. has at least one solution).
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* <hr>
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* <i>
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* Copyright (C) 2007 Paul Singleton<p>
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* Copyright (C) 1998 Fred Dushin
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* <p>
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* <p>
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Library Public License for more details.<p>
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* </i>
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* <hr>
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* @author Fred Dushin <fadushin@syr.edu>
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* @version $Revision: 1.2 $
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*/
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// Implementation notes:
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//
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//----------------------------------------------------------------------/
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public class Query implements Enumeration {
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//==================================================================/
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// Attributes
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//==================================================================/
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private static Map m = new Hashtable(); // maps (engine_t) engine handle to (Query) topmost query
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/**
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* the Compound (hence perhaps an Atom, but not Integer, Float or Variable) corresponding to the goal of this Query
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*/
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protected final Compound goal_; // set by all initialisers
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protected final String hostModule = "user"; // until revised constructors allow this to be specified
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protected final String contextModule = "user"; // until revised constructors allow this to be specified
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/**
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* @deprecated Use .goal().name() instead.
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* @return the name of this Query's goal (redundant, deprecated)
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*/
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public final String name() {
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return goal_.name(); // it can only be a Compound or Atom
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}
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/**
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* @deprecated Use .goal().args() instead.
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* @return the arguments of this Query's goal (redundant, deprecated)
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*/
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public final Term[] args() {
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return goal_.args();
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}
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/**
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* Returns the Compound (hence perhaps an Atom) which is the goal of this Query
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* @return a Term representing the goal of this Query
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*/
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public final Compound goal() {
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return goal_;
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}
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//==================================================================/
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// Constructors and Initialization
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//==================================================================/
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//------------------------------------------------------------------/
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// Query
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/**
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* This constructor creates a Query whose goal is the specified Term.
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* The Query is initially closed.
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* <b>NB</b> Creating an instance of the Query class does not
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* result in a call to a Prolog engine.
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* <b>NB</b> The goal can be a Compound or an Atom (Atom extends Compound), but cannot be an instance
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* of jpl.Float, jpl.Integer or jpl.Variable.
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* @param t the goal of this Query
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*/
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public Query(Term t) { // formerly insisted (confusingly) on a Compound (or Atom)
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this.goal_ = Query1(t);
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}
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private Compound Query1(Term t) {
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if (t instanceof Compound) {
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return (Compound) t;
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} else if (t instanceof Integer) {
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throw new JPLException("a Query's goal must be an Atom or Compound (not an Integer)");
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} else if (t instanceof Float) {
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throw new JPLException("a Query's goal must be an Atom or Compound (not a Float)");
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} else if (t instanceof Variable) {
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throw new JPLException("a Query's goal must be an Atom or Compound (not a Variable)");
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} else {
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throw new JPLException("a Query's goal must be an Atom or Compound");
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}
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}
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// Query
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/**
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* If text denotes an atom, this constructor is shorthand for
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* <font face="monospace">new Query(new Compound(name,args))</font>,
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* but if text denotes a term containing N query (?) symbols
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* and there are N args, each query is replaced by its corresponding arg
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* to provide the new Query's goal.
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*
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* @param text the name of the principal functor of this Query's goal
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* @param args the arguments of this Query's goal
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*/
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public Query(String text, Term[] args) {
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this(Query1(text, args));
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}
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// convenience case for a single arg
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public Query(String text, Term arg) {
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this(Query1(text, new Term[] { arg }));
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}
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private static Term Query1(String text, Term[] args) {
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Term t = Util.textToTerm(text);
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if (t instanceof Atom) {
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return new Compound(text, args);
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} else {
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return t.putParams(args);
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}
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}
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// Query
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/**
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* This constructor builds a Query from the given Prolog source text.
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* Throws PrologException containing error(syntax_error(_),_) if text is invalid.
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*
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* @param text the Prolog source text of this Query
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*/
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public Query(String text) {
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this(Util.textToTerm(text));
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}
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//==================================================================/
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// Making Prolog Queries
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//==================================================================/
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/**
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* These variables are used and set across the hasMoreElements
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* and nextElement Enumeration interface implementation
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*/
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private boolean open = false;
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// the following state variables are used and defined only if this query is open:
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// private boolean called = false; // open/get/close vs. hasMoreSolutions/nextSolution
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private engine_t engine = null; // handle of attached Prolog engine iff open, else null
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private Query subQuery = null; // the open Query (if any) on top of which this open Query is stacked, else null
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private predicate_t predicate = null; // handle of this Query's predicate iff open, else undefined
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// private fid_t fid = null; // id of current Prolog foreign frame iff open, else null
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// private fid_t fid2 = null; // id of experimental inner frame
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private term_t term0 = null; // term refs of this Query's args iff open, else undefined
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private qid_t qid = null; // id of current Prolog query iff open, else null
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//------------------------------------------------------------------/
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// hasMoreSolutions
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/**
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* This method returns true if JPL was able to initiate a "call" of this
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* Query within a Prolog engine. It is designed to be used
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* with the nextSolution() method to retrieve one or
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* more substitutions in the form of Hashtables. To iterate through
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* all the solutions to a Query, for example, one might write
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* <pre>
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* Query q = // obtain Query reference
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* while (q.hasMoreSolutions()) {
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* Hashtable solution = q.nextSolution();
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* // process solution...
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* }
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* </pre>
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* To ensure thread-safety, you should wrap sequential calls to
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* this method in a synchronized block, using the static
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* lock method to obtain the monitor.
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* <pre>
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* Query q = // obtain Query reference
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* synchronized ( jpl.Query.lock() ){
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* while ( q.hasMoreElements() ){
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* Hashtable solution = q.nextSolution();
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* // process solution...
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* }
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* }
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* </pre>
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*
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* @return true if the Prolog query succeeds; otherwise false.
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*/
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public synchronized final boolean hasMoreSolutions() {
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if (!open) {
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open();
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}
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return get1();
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}
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//------------------------------------------------------------------/
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// open
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/**
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* This method returns true if JPL was able to initiate a "call" of this
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* Query within the Prolog engine. It is designed to be used
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* with the getSolution() and close() methods to retrieve one or
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* more substitutions in the form of Hashtables.
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* To ensure thread-safety, you should wrap sequential calls to
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* this method in a synchronized block, using the static
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* lock method to obtain the monitor.
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* <pre>
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* Query q = // obtain Query reference
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* synchronized ( jpl.Query.lock() ){
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* while ( q.hasMoreElements() ){
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* Hashtable solution = q.nextSolution();
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* // process solution...
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* }
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* }
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* </pre>
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* <p>
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* If this method is called on an already-open Query,
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* or if the query cannot be set up for whatever reason,
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* then a JPLException will be thrown.
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*/
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public synchronized final void open() {
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if (open) {
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throw new JPLException("Query is already open");
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}
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// int self = Prolog.thread_self();
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// System.out.println("JPL thread_self()=" + self);
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if (Prolog.thread_self() == -1) { // this Java thread has no attached Prolog engine?
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engine = Prolog.attach_pool_engine(); // may block for a while, or fail
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// System.out.println("JPL attaching engine[" + engine.value + "] for " + this.hashCode() + ":" + this.toString());
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} else { // this Java thread has an attached engine
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engine = Prolog.current_engine();
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// System.out.println("JPL reusing engine[" + engine.value + "] for " + this.hashCode() + ":" + this.toString());
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}
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if (m.containsKey(new Long(engine.value))) {
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subQuery = (Query) m.get(new Long(engine.value)); // get this engine's previous topmost query
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// System.out.println("JPL reusing engine[" + engine.value + "] pushing " + subQuery.hashCode() + ":" + subQuery.toString());
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} else {
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subQuery = null;
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}
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m.put(new Long(engine.value), this); // update this engine's topmost query
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//
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// here, we must check for a module prefis, e.g. jpl:jpl_modifier_bit(volatile,T)
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String module;
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Term goal;
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if (goal_.hasFunctor(":", 2)) {
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if (goal_.arg(1).isAtom()) {
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module = goal_.arg(1).name();
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} else if (goal_.arg(1).isVariable()) {
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throw new PrologException(Util.textParamsToTerm("error(instantiation_error,?)", new Term[] { goal_ }));
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} else {
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throw new PrologException(Util.textParamsToTerm("error(type_error(atom,?),?)", new Term[] { goal_.arg(1), goal_ }));
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}
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goal = goal_.arg(2);
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} else {
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module = contextModule;
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goal = goal_;
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}
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predicate = Prolog.predicate(goal.name(), goal.arity(), module); // was hostModule
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// fid = Prolog.open_foreign_frame(); // always succeeds?
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Map varnames_to_vars = new Hashtable();
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term0 = Term.putTerms(varnames_to_vars, goal.args());
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// THINKS: invert varnames_to_Vars and use it when getting substitutions?
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qid = Prolog.open_query(Prolog.new_module(Prolog.new_atom(contextModule)), Prolog.Q_CATCH_EXCEPTION, predicate, term0);
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open = true;
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// called = false;
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}
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private final boolean get1() { // try to get the next solution; if none, close the query;
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// if (fid2 != null) { // PS 23/Mar/2007 ensure inner frame is closed
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// Prolog.close_foreign_frame(fid2);
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// fid2 = null;
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// }
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if (Prolog.next_solution(qid)) {
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// fid2 = Prolog.open_foreign_frame(); // PS 23/Mar/2007 open an inner frame
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// called = true; // OK to call get2()
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return true;
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} else {
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// if failure was due to throw/1, build exception term and throw it
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term_t exception_term_t = Prolog.exception(qid);
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if (exception_term_t.value != 0L) {
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Term exception_term = Term.getTerm(new Hashtable(), exception_term_t);
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close();
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throw new PrologException(exception_term);
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} else {
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close();
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return false;
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}
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}
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}
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//------------------------------------------------------------------/
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// getSolution
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/**
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* This method returns a java.util.Hashtable, which represents
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* a set of bindings from the names of query variables to terms within the solution.
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* <p>
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* For example, if a Query has an occurrence of a jpl.Variable,
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* say, named "X", one can obtain the Term bound to "X" in the solution
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* by looking up "X" in the Hashtable.
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* <pre>
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* Variable x = new Variable("X");
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* Query q = // obtain Query reference (with x in the Term array)
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* while (q.hasMoreSolutions()) {
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* Hashtable solution = q.nextSolution();
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* // make t the Term bound to "X" in the solution
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* Term t = (Term) solution.get("X");
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* // ...
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* }
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* </pre>
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* Programmers should obey the following rules when using this method.
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* <menu>
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* <li> The nextSolution() method should only be called after the
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* hasMoreSolutions() method returns true; otherwise a JPLException
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* will be raised, indicating that the Query is no longer open.
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* <li> The nextSolution() and hasMoreSolutions() should be called
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* in the same thread of execution, for a given Query
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* instance.
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* </menu>
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*
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* This method will throw a JPLException if Query is not open.
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*
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* @return A Hashtable representing a substitution, or null
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*/
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public synchronized final Hashtable getSolution() {
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// oughta check: Query is open and thread has its engine
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if (get1()) {
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return get2();
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} else {
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return null;
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}
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}
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public synchronized final Hashtable getSubstWithNameVars() {
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// oughta check: Query is open and thread has its engine
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if (get1()) {
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return get2WithNameVars();
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} else {
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return null;
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}
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}
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//------------------------------------------------------------------/
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// nextSolution
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/**
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* This method returns a java.util.Hashtable, which represents
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* a binding from the names of query variables to terms within the solution.
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* <p>
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* For example, if a Query has an occurrence of a jpl.Variable,
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* say, named "X", one can obtain the Term bound to "X" in the solution
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* by looking up "X" in the Hashtable.
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* <pre>
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* Variable x = new Variable("X");
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* Query q = // obtain Query reference (with x in the Term array)
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* while (q.hasMoreSolutions()) {
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* Hashtable solution = q.nextSolution();
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* // make t the Term bound to "X" in the solution
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* Term t = (Term) solution.get("X");
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* // ...
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* }
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* </pre>
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* Programmers should obey the following rules when using this method.
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* <menu>
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* <li> The nextSolution() method should only be called after the
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* hasMoreSolutions() method returns true; otherwise a JPLException
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* will be raised, indicating that the Query is no longer open.
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* <li> The nextSolution() and hasMoreSolutions() should be called
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* in the same thread of execution, for a given Query
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* instance.
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* </menu>
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*
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* This method will throw a JPLException if Query is not open.
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*
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* @return A Hashtable representing a substitution.
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*/
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public synchronized final Hashtable nextSolution() {
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return get2();
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}
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private final Hashtable get2() {
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if (!open) {
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throw new JPLException("Query is not open");
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} else {
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Hashtable substitution = new Hashtable();
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// NB I reckon computeSubstitutions needn't be in Term (but where else?)
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Term.getSubsts(substitution, new Hashtable(), goal_.args);
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return substitution;
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}
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}
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// assumes that Query's last arg is a Variable which will be bound to a [Name=Var,..] dict
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private final Hashtable get2WithNameVars() {
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if (!open) {
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throw new JPLException("Query is not open");
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} else {
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Term[] args = goal_.args; // for slight convenience below
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Term argNV = args[args.length - 1]; // the Query's last arg
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String nameNV = ((Variable) argNV).name; // its name
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// get the [Name=Var,..] dict from the last arg
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Map varnames_to_Terms1 = new Hashtable();
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Map vars_to_Vars1 = new Hashtable();
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args[args.length - 1].getSubst(varnames_to_Terms1, vars_to_Vars1);
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Hashtable varnames_to_Terms2 = new Hashtable();
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Term nvs = (Term) varnames_to_Terms1.get(nameNV);
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Map vars_to_Vars2 = Util.namevarsToMap(nvs);
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for (int i = 0; i < args.length - 1; ++i) {
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args[i].getSubst(varnames_to_Terms2, vars_to_Vars2);
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}
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return varnames_to_Terms2;
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}
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}
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//------------------------------------------------------------------/
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// hasMoreElements
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/**
|
|
* This method implements part of the java.util.Enumeration
|
|
* interface. It is a wrapper for hasMoreSolutions.
|
|
*
|
|
* @return true if the Prolog query yields a (or another) solution, else false.
|
|
*/
|
|
public synchronized final boolean hasMoreElements() {
|
|
return hasMoreSolutions();
|
|
}
|
|
//------------------------------------------------------------------/
|
|
// nextElement
|
|
/**
|
|
* This method implements part of the java.util.Enumeration
|
|
* interface. It is a wrapper for nextSolution.
|
|
* <p>
|
|
*
|
|
* @return A Hashtable representing a substitution.
|
|
*/
|
|
public synchronized final Object nextElement() {
|
|
return nextSolution();
|
|
}
|
|
public synchronized final void rewind() {
|
|
close();
|
|
}
|
|
/**
|
|
* This method can be used to close an open query before its solutions are exhausted.
|
|
* It is called automatically when solutions are exhausted, i.e. when hasMoreSolutions() fails.
|
|
* Calling close() on an already closed Query is harmless (has no effect).<p>
|
|
*
|
|
* Here is one way to get the first three solutions to a Query:
|
|
* <pre>
|
|
* Query q = new Query(predicate, args);
|
|
* Hashtable sub1 = (Hashtable) q.nextSolution();
|
|
* Hashtable sub2 = (Hashtable) q.nextSolution();
|
|
* Hashtable sub3 = (Hashtable) q.nextSolution();
|
|
* q.close();
|
|
* </pre><p>
|
|
*/
|
|
public synchronized 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");
|
|
}
|
|
Query topmost = (Query) m.get(new Long(engine.value));
|
|
if (topmost != this) {
|
|
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
|
|
m.remove(new Long(engine.value));
|
|
if (subQuery == 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 {
|
|
m.put(new Long(engine.value), subQuery);
|
|
// System.out.println("JPL retaining engine[" + engine.value + "] popping subQuery(" + subQuery.hashCode() + ":" + subQuery.toString() + ")");
|
|
}
|
|
open = false; // this Query is now closed
|
|
engine = null; // this Query, being closed, is no longer associated with any Prolog engine
|
|
subQuery = null; // this Query, being closed, is not stacked upon any other Query
|
|
}
|
|
/**
|
|
* calls the Query's goal to exhaustion
|
|
* and returns an array of zero or more Hashtables of zero or more variablename-to-term bindings (each Hashtable represents a solution, in the order in which they were found).
|
|
* @return an array of zero or more Hashtables of zero or more variablename-to-term bindings (each Hashtable represents a solution, in the order in which they were found)
|
|
* <b>NB</b> in JPL 1.0.1, this method (inconsistently) returned null when a Query had no solutions;
|
|
* in JPL 2.x onwards it returns an empty array (thus the length of the array is, in every case,
|
|
* the quantity of solutions).<p>
|
|
* <b>NB</b> in JPL 1.0.1, bindings were keyed (awkwardly) by Variable instances;
|
|
* in JPL 2.x onwards they are keyed by the (String) names of variables,
|
|
* which is consistent with the Term type being just a concrete syntax for terms (and hence queries).<p>
|
|
*/
|
|
public synchronized final Hashtable[] allSolutions() {
|
|
if (open) {
|
|
throw new JPLException("Query is already open");
|
|
} else {
|
|
// get a vector of solutions:
|
|
Vector v = new Vector();
|
|
while (hasMoreSolutions()) {
|
|
v.addElement(nextSolution());
|
|
}
|
|
// turn the vector into an array:
|
|
Hashtable solutions[] = new Hashtable[v.size()]; // 0 solutions -> Hashtable[0]
|
|
v.copyInto(solutions);
|
|
return solutions;
|
|
}
|
|
}
|
|
/**
|
|
* This static method creates a Query whose goal is the given Term,
|
|
* calls it to exhaustion,
|
|
* and returns an array of zero or more Hashtables of zero or more variablename-to-term bindings (each Hashtable represents a solution, in the order in which they were found).
|
|
* Throws JPLException if goal is neither a jpl.Atom nor a jpl.Compound.
|
|
*
|
|
* @return an array of zero or more Hashtables of zero or more variablename-to-term bindings (each Hashtable represents a solution, in the order in which they were found)
|
|
*
|
|
* @param goal the goal of this Query
|
|
*/
|
|
public static final Hashtable[] allSolutions(Term goal) {
|
|
return (new Query(goal)).allSolutions();
|
|
}
|
|
/**
|
|
* This static method creates a Query from the given Prolog source text fragment,
|
|
* calls it to exhaustion,
|
|
* and returns an array of zero or more Hashtables of zero or more variablename-to-term bindings (each Hashtable represents a solution, in the order in which they were found).
|
|
* Throws PrologException containing error(syntax_error(_),_) if text is invalid.
|
|
*
|
|
* @return an array of zero or more Hashtables of zero or more variablename-to-term bindings (each Hashtable represents a solution, in the order in which they were found)
|
|
*
|
|
* @param text a Prolog source text fragment denoting a goal
|
|
*/
|
|
public static final Hashtable[] allSolutions(String text) {
|
|
return (new Query(text)).allSolutions();
|
|
}
|
|
/**
|
|
* If text denotes (in traditional Prolog source syntax) a term containing N questionmark (?) symbols and there are N accompanying Term params,
|
|
* this static method replaces each questionmark symbol by its respective param,
|
|
* calls the resulting goal to exhaustion,
|
|
* and returns an array of zero or more Hashtables of zero or more variablename-to-term bindings (each Hashtable represents a solution, in the order in which they were found).
|
|
*
|
|
* Otherwise, if text denotes an atom, this static method creates a Query
|
|
* where text is the name of the goal and params are the args;
|
|
* the resulting goal is then called as above.
|
|
* This letter mode is redundant, deprecated (informally), and retained only for backward compatibility.
|
|
*
|
|
* @return an array of zero or more Hashtables of zero or more variablename-to-term bindings (each Hashtable represents a solution, in the order in which they were found)
|
|
*
|
|
* @param text the Prolog source text of a goal, in which questionmarks are regarded as substitutible parameters
|
|
* @param params terms to be substituted for the respective questionmarks in the query text
|
|
*/
|
|
public static final Hashtable[] allSolutions(String text, Term[] params) {
|
|
return (new Query(text, params)).allSolutions();
|
|
}
|
|
/**
|
|
* calls the Query's goal to exhaustion or until N solutions are found, whichever is sooner,
|
|
* and returns an array containing (as possibly empty Hashtables of variablename-to-term bindings) every found solution (in the order in which they were found).
|
|
* @return an array of Hashtables (possibly none), each of which is a solution
|
|
* (in the order in which they were found) of the Query; at most 'n' solutions will be found and returned.
|
|
* <b>NB</b> in JPL 1.0.1, this method (inconsistently) returned null when a Query had no solutions;
|
|
* in JPL 2.x onwards it returns an empty array (thus the length of the array is, in every case,
|
|
* the quantity of solutions).<p>
|
|
* <b>NB</b> in JPL 1.0.1, bindings were keyed (awkwardly) by Variable instances;
|
|
* in JPL 2.x onwards they are keyed by the (String) names of variables,
|
|
* which is consistent with the Term type being just a concrete syntax for terms (and hence queries).<p>
|
|
*/
|
|
public synchronized final Hashtable[] nSolutions(long n) {
|
|
if (open) {
|
|
throw new JPLException("Query is already open");
|
|
} else {
|
|
// get a vector of solutions:
|
|
Vector v = new Vector();
|
|
for (long i = 0; i++ < n && hasMoreSolutions();) {
|
|
v.addElement(nextSolution());
|
|
}
|
|
// turn the vector into an array:
|
|
Hashtable solutions[] = new Hashtable[v.size()]; // 0 solutions -> Hashtable[0]
|
|
v.copyInto(solutions);
|
|
return solutions;
|
|
}
|
|
}
|
|
/**
|
|
* This static method creates a Query whose goal is the given Term,
|
|
* calls it to exhaustion or until N solutions are found, whichever is sooner,
|
|
* and returns an array containing (as possibly empty Hashtables of variablename-to-term bindings) every found solution (in the order in which they were found).
|
|
* Throws JPLException if goal is neither a jpl.Atom nor a jpl.Compound.
|
|
*
|
|
* @param goal the goal of this Query
|
|
*/
|
|
public static final Hashtable[] nSolutions(Term goal, long n) {
|
|
return (new Query(goal)).nSolutions(n);
|
|
}
|
|
/**
|
|
* This static method creates a Query from the given Prolog source text fragment,
|
|
* calls it to exhaustion or until N solutions are found, whichever is sooner,
|
|
* and returns an array containing (as possibly empty Hashtables of variablename-to-term bindings) every found solution (in the order in which they were found).
|
|
* Throws PrologException containing error(syntax_error(_),_) if text is invalid.
|
|
*
|
|
* @param text a Prolog source text fragment denoting a goal
|
|
*/
|
|
public static final Hashtable[] nSolutions(String text, long n) {
|
|
return (new Query(text)).nSolutions(n);
|
|
}
|
|
/**
|
|
* If text denotes (in traditional Prolog source syntax) a term containing N questionmark (?) symbols and there are N accompanying params,
|
|
* this static method replaces each questionmark symbol by its respective param,
|
|
* calls the resulting goal to exhaustion or until N solutions are found, whichever is sooner,
|
|
* and returns an array containing (as possibly empty Hashtables of variablename-to-term bindings) every found solution (in the order in which they were found).
|
|
*
|
|
* Otherwise, if text denotes an atom, this static method creates a Query
|
|
* where text is the name of the goal and params are the args;
|
|
* the resulting goal is then called as above.
|
|
* This latter mode is redundant, deprecated (informally), and retained only for backward compatibility.
|
|
*
|
|
* @param text the Prolog source text of a goal, in which questionmarks are regarded as substitutible parameters
|
|
* @param params terms to be substituted for the respective questionmarks in the query text
|
|
*/
|
|
public static final Hashtable[] nSolutions(String text, Term[] params, long n) {
|
|
return (new Query(text, params)).nSolutions(n);
|
|
}
|
|
/**
|
|
* Returns the first solution, if any, as a (possibly empty) Hashtable of variablename-to-term bindings, else null.
|
|
*
|
|
* This method will throw a JPLException if this Query is already open (and the Query will remain open as before).
|
|
* Otherwise, upon return, the Query will be closed.
|
|
* @return the first solution, if the query has one, as a (possibly empty) Hashtable.
|
|
* If the return value is null, this means that the Query has no solutions.<p>
|
|
*/
|
|
public synchronized final Hashtable oneSolution() {
|
|
if (open) {
|
|
throw new JPLException("Query is already open");
|
|
} else {
|
|
Hashtable solution;
|
|
if (hasMoreSolutions()) {
|
|
solution = nextSolution();
|
|
close(); // safe, whether or not this is the only solution
|
|
} else {
|
|
solution = null;
|
|
}
|
|
return solution;
|
|
}
|
|
}
|
|
/**
|
|
* This static method creates a Query (whose goal is the specified Term)
|
|
* and calls it at most once, returning the first solution, if there is one, as a (possibly empty) Hashtable, else null.
|
|
* The goal can be a jpl.Atom or a jpl.Compound, but cannot be an instance
|
|
* of jpl.Float, jpl.Integer or jpl.Variable.
|
|
*
|
|
* @param goal the goal of this Query
|
|
*/
|
|
public static final Hashtable oneSolution(Term goal) {
|
|
return (new Query(goal)).oneSolution();
|
|
}
|
|
/**
|
|
* This static method creates a Query from the given Prolog source text fragment,
|
|
* and calls it at most once, returning the first solution, if there is one, as a (possibly empty) Hashtable, else null.
|
|
* Throws PrologException containing error(syntax_error(_),_) if text is invalid.
|
|
*
|
|
* @param text a Prolog source text fragment denoting a goal
|
|
*/
|
|
public static final Hashtable oneSolution(String text) {
|
|
return (new Query(text)).oneSolution();
|
|
}
|
|
/**
|
|
* If text denotes (in traditional Prolog source syntax) a term containing N questionmark (?) symbols
|
|
* and there are N params, each questionmark symbol is replaced by its respective param
|
|
* to provide the goal of this query:
|
|
* the resulting goal is then called (at most once) and the first solution, if there is one, is returned as a (possibly empty) Hashtable, else null.
|
|
*
|
|
* Otherwise, if text denotes an atom, this static method creates a Query
|
|
* where text is the name of the goal and params are the args;
|
|
* the resulting goal is then called as above.
|
|
* This latter mode is redundant, deprecated (informally), and retained only for backward compatibility.
|
|
*
|
|
* @param text the Prolog source text of a goal, in which questionmarks are regarded as substitutible parameters
|
|
* @param params terms to be substituted for the respective questionmarks in the query text
|
|
*/
|
|
public static final Hashtable oneSolution(String text, Term[] params) {
|
|
return (new Query(text, params)).oneSolution();
|
|
}
|
|
/**
|
|
* This method will attempt to call this Query's goal within an available Prolog engine.
|
|
* @return the provability of the Query, i.e. 'true' if it has at least
|
|
* one solution, 'false' if the call fails without finding a solution.<p>
|
|
*
|
|
* Only the first solution (if there is one) will be found;
|
|
* any bindings will be discarded, and the Query will be closed.<p>
|
|
* This method will throw a JPLException if this Query is already open.
|
|
*
|
|
* @deprecated Use .hasSolution() instead.
|
|
*/
|
|
public synchronized final boolean query() {
|
|
return oneSolution() != null;
|
|
}
|
|
/**
|
|
* This method will attempt to call this Query's goal within an available Prolog engine.
|
|
* @return the provability of the Query, i.e. 'true' if it has at least
|
|
* one solution, 'false' if the call fails without finding a solution.<p>
|
|
*
|
|
* Only the first solution (if there is one) will be found;
|
|
* any bindings will be discarded, and the Query will be closed.<p>
|
|
* This method will throw a JPLException if this Query is already open.
|
|
*/
|
|
public synchronized final boolean hasSolution() {
|
|
return oneSolution() != null;
|
|
}
|
|
/**
|
|
* This static method creates a Query (whose goal is the specified Term)
|
|
* and calls it at most once, returning true if a solution was found, else false.
|
|
* The goal can be a jpl.Atom or a jpl.Compound, but cannot be an instance
|
|
* of jpl.Float, jpl.Integer or jpl.Variable.
|
|
*
|
|
* @param goal the goal of this Query
|
|
*/
|
|
public static final boolean hasSolution(Term goal) {
|
|
return (new Query(goal)).hasSolution();
|
|
}
|
|
/**
|
|
* This static method creates a Query from the given Prolog source text
|
|
* and calls it at most once, returning true if a solution was found, else false.
|
|
* Throws PrologException containing error(syntax_error(_),_) if text is invalid.
|
|
*
|
|
* @param text the goal of this Query, as Prolog source text
|
|
*/
|
|
public static final boolean hasSolution(String text) {
|
|
return (new Query(text)).hasSolution();
|
|
}
|
|
/**
|
|
* If text denotes (in traditional Prolog source syntax) a term containing N questionmark (?) symbols
|
|
* and there are N params, each questionmark symbol is replaced by its corresponding arg
|
|
* to provide the new Query's goal: the resulting Query is called as described above.
|
|
*
|
|
* Otherwise, if text denotes an atom, this static method creates a Query
|
|
* where text is the name of its goal and args are its args;
|
|
* it then calls this goal (at most once) and returns true if a solution was found, else false.
|
|
* This latter mode is redundant, deprecated (informally), and retained only for backward compatibility.
|
|
*
|
|
* @param text the Prolog source text of a goal, in which questionmarks are regarded as substitutible parameters
|
|
* @param params terms to be substituted for the respective questionmarks in the query text
|
|
*/
|
|
public static final boolean hasSolution(String text, Term[] params) {
|
|
return (new Query(text, params)).hasSolution();
|
|
}
|
|
//
|
|
// this method doesn't work, but is intended to be called from another thread,
|
|
// to abort a Query which is open and possibly currently executing nextSolution() or similar
|
|
public final int abort() {
|
|
if (open) {
|
|
(new Thread(new Runnable() {
|
|
public void run() {
|
|
try {
|
|
int rc1 = Prolog.attach_engine(engine);
|
|
System.out.println("q.abort(): attach_engine() returns " + rc1);
|
|
int rc2 = Prolog.action_abort();
|
|
System.out.println("q.abort(): action_abort() returns " + rc2);
|
|
// int rc3 = Prolog.release_pool_engine();
|
|
// System.out.println("q.abort(): release_pool_engine() returns " + rc3);
|
|
} catch (Exception e) {
|
|
}
|
|
}
|
|
})).start(); // call the query in a separate thread
|
|
/*
|
|
int rc0a = Prolog.pool_engine_id(this.engine);
|
|
System.out.println("q.abort(): this.engine has id=" + rc0a);
|
|
|
|
engine_t e = Prolog.current_engine();
|
|
System.out.println("q.abort(): " + (e == null ? "no current engine" : "current engine id=" + Prolog.pool_engine_id(e)));
|
|
|
|
int rc0b = Prolog.release_pool_engine();
|
|
System.err.println("q.abort(): release_pool_engine() returns " + rc0b);
|
|
|
|
engine_t e2 = Prolog.current_engine();
|
|
System.out.println("q.abort(): " + (e == null ? "no current engine" : "current engine id=" + Prolog.pool_engine_id(e2)));
|
|
|
|
int rc1 = Prolog.attach_engine(this.engine);
|
|
System.out.println("q.abort(): attach_engine() returns " + rc1);
|
|
|
|
engine_t e3 = Prolog.current_engine();
|
|
System.out.println("q.abort(): " + (e == null ? "no current engine" : "current engine id=" + Prolog.pool_engine_id(e3)));
|
|
|
|
int rc2 = Prolog.action_abort();
|
|
System.out.println("q.abort(): action_abort() returns " + rc2);
|
|
|
|
int rc3 = Prolog.release_pool_engine();
|
|
System.out.println("q.abort(): release_pool_engine() returns " + rc3);
|
|
|
|
int rc4 = Prolog.attach_engine(e);
|
|
System.out.println("q.abort(): attach_engine() returns " + rc4);
|
|
*/
|
|
return 0;
|
|
} else {
|
|
System.out.println("q.abort(): query is not open");
|
|
return -1;
|
|
}
|
|
}
|
|
//==================================================================/
|
|
// misc
|
|
//==================================================================/
|
|
/**
|
|
* Returns a crude String representation of a Query.
|
|
*
|
|
* @return a crude String representation of a Query
|
|
*/
|
|
public String toString() {
|
|
return goal_.name + "( " + Term.toString(goal_.args) + " )";
|
|
}
|
|
//==================================================================/
|
|
// Methods (deprecated)
|
|
//==================================================================/
|
|
/**
|
|
* Returns a debug-friendly representation of a Query
|
|
*
|
|
* @return a debug-friendly representation of a Query
|
|
* @deprecated
|
|
*/
|
|
public String debugString() {
|
|
return "(Query " + goal_.name + " " + Term.debugString(goal_.args) + ")";
|
|
}
|
|
}
|