jpl stuff

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

LGPL/JPL/java/jpl/Atom.java

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+//tabstop=4
+//*****************************************************************************/
+// Project: jpl
+//
+// File:    $Id: Atom.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.StringHolder;
+import jpl.fli.term_t;
+
+//----------------------------------------------------------------------/
+// Atom
+/**
+ * Atom is a specialised Compound with zero arguments, representing a Prolog atom with the same name.
+ * An Atom is constructed with a String parameter (its name, unquoted), which cannot thereafter be changed.
+ * <pre>Atom a = new Atom("hello");</pre>
+ * An Atom can be used (and re-used) as an argument of Compound Terms.
+ * Two Atom instances are equal (by equals()) iff they have equal names.
+ * 
+ * <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 Atom extends Compound {
+
+	//==================================================================/
+	//  Attributes (none)
+	//==================================================================/
+
+	//==================================================================/
+	//  Constructors
+	//==================================================================/
+
+	/**
+	 * @param   name   the Atom's name (unquoted)
+	 */
+	public Atom(String name) {
+		super(name);
+	}
+
+	//==================================================================/
+	//  Methods (common)
+	//==================================================================/
+
+	// these are all inherited from Compound
+
+	public final int type() {
+		return Prolog.ATOM;
+	}
+	
+	//==================================================================/
+	//  Methods (deprecated)
+	//==================================================================/
+
+	/**
+	 * Returns a debug-friendly String representation of an Atom.
+	 * 
+	 * @return  a debug-friendly String representation of an Atom
+	 * @deprecated
+	 */
+	public String debugString() {
+		return "(Atom " + toString() + ")";
+	}
+
+	//==================================================================/
+	//  Converting JPL Terms to Prolog terms
+	//==================================================================/
+
+	// (this is done with the put() method inherited from Compound)
+
+	//==================================================================/
+	//  Converting Prolog terms to JPL Terms
+	//==================================================================/
+
+	/**
+	 * Converts a Prolog term to a JPL Atom.  This is only called from Term.getTerm(),
+	 * and we can assume the term_t refers to a Prolog atom,
+	 * so we just create a new Atom object with the atom's name.
+	 *
+	 * @param   vars_to_Vars  A Map from Prolog variables to JPL Variables.
+	 * @param   term          The Prolog term to be converted
+	 * @return                A new Atom instance
+	 */
+	protected static Term getTerm(Map vars_to_Vars, term_t term) {
+		StringHolder holder = new StringHolder();
+		Prolog.get_atom_chars(term, holder); // ignore return val; assume success...
+
+		return new Atom(holder.value);
+	}
+
+	/**
+	 * Converts a term_t to an Atom, knowing that it refers to a SWI-Prolog string,
+	 * so we just create a new Atom object initialised with the string's value.
+	 * JPL users should avoid SWI-Prolog's non-ISO strings, but in some obscure
+	 * circumstances they are returned unavoidably, so we have to handle them
+	 * (and this is how).
+	 *
+	 * @param   vars_to_Vars  A Map from Prolog variables to JPL Variables.
+	 * @param   term          The term_t to convert
+	 * @return                A new Atom instance
+	 */
+	protected static Term getString(Map vars_to_Vars, term_t term) {
+		StringHolder holder = new StringHolder();
+		Prolog.get_string_chars(term, holder); // ignore return val; assume success...
+		// System.err.println("Warning: Prolog returns a string: \"" + holder.value + "\"");
+		return new Atom(holder.value);
+	}
+
+	//==================================================================/
+	//  Computing substitutions
+	//==================================================================/
+
+	// (done with the inherited Compound.getSubst() method)
+
+}
+
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