jpl stuff
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LGPL/JPL/java/jpl/JRef.java
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LGPL/JPL/java/jpl/JRef.java
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//*****************************************************************************/
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// Project: jpl
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//
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// File: $Id: JRef.java,v 1.1 2004-08-27 20:27:56 vsc Exp $
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// Date: $Date: 2004-08-27 20:27:56 $
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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.Map;
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import jpl.fli.ObjectHolder;
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import jpl.fli.Prolog;
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import jpl.fli.term_t;
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//----------------------------------------------------------------------/
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// JRef
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/**
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* JRef is a specialised Term with an Object field, representing JPL's Prolog references to Java objects (or to null).
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* <pre>
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* JRef r = new JRef( non_String_object_or_null );
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* </pre>
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* A JRef can be used (and re-used) in Compound Terms.
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*
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* <hr><i>
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* Copyright (C) 2004 Paul Singleton<p>
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* Copyright (C) 1998 Fred Dushin<p>
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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.<p>
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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.<p>
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* </i><hr>
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* @author Fred Dushin <fadushin@syr.edu>
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* @version $Revision: 1.1 $
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* @see jpl.Term
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* @see jpl.Compound
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*/
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public class JRef extends Term {
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//==================================================================/
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// Attributes
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//==================================================================/
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/**
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* the JRef's value (a non-String Object or null)
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*/
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protected final Object ref;
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//==================================================================/
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// Constructors
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//==================================================================/
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/**
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* This constructor creates a JRef, initialized with the supplied
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* non-String object (or null).
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*
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* @param ref this JRef's value (a non-String object, or null)
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*/
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public JRef(Object ref) {
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if (ref instanceof String) {
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throw new JPLException("a JRef cannot have a String value (String maps to atom)");
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} else {
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this.ref = ref;
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}
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}
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//==================================================================/
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// Methods (common)
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//==================================================================/
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/**
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* Returns a Prolog source text representation of this JRef
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*
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* @return a Prolog source text representation of this JRef
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*/
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public String toString() {
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return "" + ref + ""; // WRONG
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}
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/**
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* Two JRefs are equal if their references are identical (?)
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*
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* @param obj The Object to compare
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* @return true if the Object satisfies the above condition
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*/
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public final boolean equals(Object obj) {
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return this == obj || (obj instanceof JRef && ref == ((JRef) obj).ref);
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}
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public final int type() {
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return Prolog.JREF;
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}
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public String typeName(){
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return "JRef";
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}
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//==================================================================/
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// Methods (peculiar)
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//==================================================================/
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/**
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* The non-String object (or null) which this jpl.JRef represents
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*
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* @return the non-String object (or null) which this jpl.JRef represents
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*/
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public Object ref() {
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return ref;
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}
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//==================================================================/
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// Methods (deprecated)
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//==================================================================/
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/**
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* The (nonexistent) args of this JRef
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*
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* @return the (nonexistent) args of this JRef
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* @deprecated
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*/
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public Term[] args() {
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return new Term[] {
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};
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}
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/**
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* Returns a debug-friendly representation of this JRef
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*
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* @return a debug-friendly representation of this JRef
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* @deprecated
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*/
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public String debugString() {
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return "(JRef " + toString() + ")";
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}
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//==================================================================/
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// Converting JPL Terms to Prolog terms
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//==================================================================/
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/**
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* To convert a JRef to a term, we put its Object field (.value) into the
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* term_t as a JPL ref (i.e. @/1) structure.
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*
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* @param varnames_to_vars A Map from variable names to Prolog variables.
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* @param term A (newly created) term_t which is to be
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* set to a Prolog 'ref' (i.e. @/1) structure denoting the
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* .value of this JRef instance
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*/
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protected final void put(Map varnames_to_vars, term_t term) {
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Prolog.put_jref(term, ref);
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}
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//==================================================================/
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// Converting Prolog terms to JPL Terms
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//==================================================================/
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/**
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* Converts a term_t to a JRef. Assuming the Prolog term is a
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* ref, we just create a new JRef using the term_t's value.
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* NB This conversion is only invoked if "JPL-aware" term import is specified.
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*
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* @param vars_to_Vars A Map from Prolog variables to JPL Variables.
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* @param term The term (a ref) to convert
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* @return A new JRef instance
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*/
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protected static Term getTerm(Map vars_to_Vars, term_t term) {
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ObjectHolder obj = new ObjectHolder();
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Prolog.get_jref(term, obj); // assume it succeeds...
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return new jpl.JRef(obj.value);
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}
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//==================================================================/
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// Computing Substitutions
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//==================================================================/
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/**
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* Nothing needs to be done if the Term is an Atom, Integer, Float or JRef
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*
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* @param varnames_to_Terms A Map from variable names to Terms.
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* @param vars_to_Vars A Map from Prolog variables to JPL Variables.
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*/
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protected final void getSubst(Map varnames_to_Terms, Map vars_to_Vars) {
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}
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}
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//345678901234567890123456789012346578901234567890123456789012345678901234567890
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