jpl stuff

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1120 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

LGPL/JPL/java/jpl/JVoid.java

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+//tabstop=4
+//*****************************************************************************/
+// Project: jpl
+//
+// File:    $Id: JVoid.java,v 1.1 2004-08-27 20:27:56 vsc Exp $
+// Date:    $Date: 2004-08-27 20:27:56 $
+// Author:  Fred Dushin <fadushin@syr.edu>
+//          
+//
+// Description:
+//    
+//
+// -------------------------------------------------------------------------
+// Copyright (c) 2004 Paul Singleton
+// Copyright (c) 1998 Fred Dushin
+//                    All rights reserved.
+// 
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Library Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+// 
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Library Public License for more details.
+//*****************************************************************************/
+package jpl;
+
+import java.util.Map;
+
+import jpl.fli.Prolog;
+import jpl.fli.term_t;
+
+//----------------------------------------------------------------------/
+// JVoid
+/**
+ * A jpl.JVoid is a specialised Term.  Instances of this class
+ * denote JPL 'jvoid' values in Prolog, i.e. @(void):
+ * <pre>
+ * JVoid b = new JVoid();
+ * </pre>
+ * A JVoid can be used (and re-used) in Compound Terms.
+ * 
+ * <hr><i>
+ * Copyright (C) 2004  Paul Singleton<p>
+ * Copyright (C) 1998  Fred Dushin<p>
+ * 
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.<p>
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library Public License for more details.<p>
+ * </i><hr>
+ * @author  Fred Dushin <fadushin@syr.edu>
+ * @version $Revision: 1.1 $
+ * @see jpl.Term
+ * @see jpl.Compound
+ */
+public class JVoid extends Term {
+	
+	//==================================================================/
+	//  Attributes (none)
+	//==================================================================/
+
+	//==================================================================/
+	//  Constructors
+	//==================================================================/
+
+	/**
+	 * This constructor creates a JVoid.
+	 * 
+	 */
+	public JVoid() {
+	}
+
+	//==================================================================/
+	//  Methods (common)
+	//==================================================================/
+
+	/**
+	 * Returns a Prolog source text representation of this JVoid
+	 * 
+	 * @return  a Prolog source text representation of this JVoid
+	 */
+	public String toString() {
+		return "@(void)";
+	}
+
+	/**
+	 * Two JVoids are equal
+	 * 
+	 * @param   obj  The Object to compare (not necessarily another JVoid)
+	 * @return  true if the Object satisfies the above condition
+	 */
+	public final boolean equals(Object obj) {
+		return this == obj || (obj instanceof JVoid);
+	}
+	
+	public final int type() {
+		return Prolog.JVOID;
+	}
+	
+	public String typeName(){
+		return "JVoid";
+	}
+	
+	//==================================================================/
+	//  Methods (deprecated)
+	//==================================================================/
+
+	/**
+	 * The (nonexistent) args of this JVoid
+	 * 
+	 * @return the (nonexistent) args of this JVoid
+	 * @deprecated
+	 */
+	public Term[] args() {
+		return new Term[] {};
+	}
+	
+	/**
+	 * Returns a debug-friendly representation of this JVoid
+	 * 
+	 * @return  a debug-friendly representation of this JVoid
+	 * @deprecated
+	 */
+	public String debugString() {
+		return "(JVoid)";
+	}
+
+	//==================================================================/
+	//  Converting JPL Terms to Prolog terms
+	//==================================================================/
+
+	/**
+	 * To convert a JVoid to a term, we unify the (freshly created, hence unbound)
+	 * term_t with @(void).
+	 * 
+	 * @param   varnames_to_vars  A Map from variable names to Prolog variables.
+	 * @param   term              A (previously created and unbound) term_t which is to be
+	 *                            assigned a Prolog @(void) structure
+	 */
+	protected final void put(Map varnames_to_vars, term_t term) {
+		Prolog.put_jvoid(term);
+	}
+
+	//==================================================================/
+	//  Converting Prolog terms to JPL Terms
+	//==================================================================/
+	
+	/**
+	 * Converts a term_t to a JVoid.  Assuming the Prolog term to be
+	 * @(void), we just create a new JVoid instance.
+	 * NB This conversion is only invoked if "JPL-aware" term import is specified.
+	 *
+	 * @param   vars_to_Vars  A Map from Prolog variables to JPL Variables.
+	 * @param   term          The term_t to convert
+	 * @return                A new JVoid instance
+	 */
+	protected static Term getTerm(Map vars_to_Vars, term_t term) {
+		return new jpl.JVoid();
+	}
+
+	//==================================================================/
+	//  Computing Substitutions
+	//==================================================================/
+
+	/**
+	 * Nothing needs to be done if the Term denotes an Atom, Integer, Float, JRef, JBoolean or JVoid
+	 * 
+	 * @param   varnames_to_Terms  A Map from variable names to Terms.
+	 * @param   vars_to_Vars       A Map from Prolog variables to JPL Variables.
+	 *                 Variables.
+	 */
+	protected final void getSubst(Map varnames_to_Terms, Map vars_to_Vars) {
+	}
+
+}
+
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