be83a4a309
git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1120 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
134 lines
4.1 KiB
Java
134 lines
4.1 KiB
Java
//tabstop=4
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//*****************************************************************************/
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// Project: jpl
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//
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// File: $Id: term_t.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) 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.fli;
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//----------------------------------------------------------------------/
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// term_t
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/**
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* A term_t is a simple class which mirrors the term_t type in
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* the Prolog FLI. All it really does is hold a term reference,
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* which is an internal representation of a term in the Prolog
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* Engine.
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*
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* <hr><i>
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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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*/
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// Implementation notes:
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//
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//----------------------------------------------------------------------/
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public class term_t
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extends LongHolder
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{
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public static final long UNASSIGNED = -1L;
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public
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term_t()
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{
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value = UNASSIGNED;
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}
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//------------------------------------------------------------------/
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// toString
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/**
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* This static method converts a term_t, which is assumed to contain
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* a reference to a *consecutive* list of term_t references to a
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* String representation of a list of terms, in this case, a comma
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* separated list.
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*
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* @param n the number of consecutive term_ts
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* @param term0 a term_t whose value is the 0th term_t.
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*/
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// Implementation notes:
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//
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//------------------------------------------------------------------/
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public static String
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toString( int n, term_t term0 )
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{
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String s = "";
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int i;
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long ith_term_t;
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for ( i = 0, ith_term_t = term0.value; i < n; ++i, ++ith_term_t ){
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term_t term = new term_t();
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term.value = ith_term_t;
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s += term.toString();
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if ( i != n - 1 ){
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s += ", ";
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}
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}
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return s;
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}
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//------------------------------------------------------------------/
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// equals
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/**
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* Instances of term_ts are stored in Term objects (see jpl.Term),
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* and these term_ts are in some cases stored in Hashtables.
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* Supplying this predicate provides the right behavior in Hashtable
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* lookup (see the rules for Hashtable lookup in java.util).<p>
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*
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* Note. Two term_ts are *not* equal if their values have not
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* been assigned. (Since Prolog FLI term_ts are unsigned values and
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* the UNASSIGNED value is -1, this should work).
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*
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* @param obj the Object to comapre.
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* @return true if the supplied object is a term_t instances
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* and the long values are the same
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*/
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// Implementation notes:
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//
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//------------------------------------------------------------------/
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public boolean
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equals( Object obj )
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{
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return
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(obj instanceof term_t) &&
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this.value == ((term_t)obj).value &&
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this.value != UNASSIGNED;
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}
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}
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