jpl.Atom Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of sigma-component Show documentation
Sigma knowledge engineering system is an system for developing, viewing and debugging theories in first order logic. It works with Knowledge Interchange Format (KIF) and is optimized for the Suggested Upper Merged Ontology (SUMO) www.ontologyportal.org.
The newest version!
/*This code is copyrighted by Teknowledge (c) 2003.
It is released underthe GNU Public License .
Users ofthis code also consent, by use of this code, to credit Teknowledge in any
writings, briefings,publications, presentations, or other representations of any
software which incorporates, builds on, or uses this code.*/ 

 
package jpl;

import java.util.Hashtable;
import jpl.fli.*;

//----------------------------------------------------------------------/
// Atom
/**
 * An Atom is a Term with a name field.  Use this class to create
 * Java representations of Prolog atoms:
 *  * Atom a = new Atom( "a" );
 * 
 * 
 * An Atom can be used (and re-used) in Compound Terms.
 * 
 * 

 * Copyright (C) 1998  Fred Dushin
 * 
 * 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.
 * 

 * @author  Fred Dushin 
 * @version $Revision: 1.1.1.1 $
 * @see jpl.Term
 * @see jpl.Compound
 */
// Implementation notes:  
// 
//----------------------------------------------------------------------/
public class Atom
extends      Term
{
	//==================================================================/
	//  Attributes
	//==================================================================/

	/**
	 * This atom's name
	 */
	protected java.lang.String name_;
	
	//------------------------------------------------------------------/
	// name
	/**
	 * @return  the name of the Atom
	 */
	// Implementation notes:  
	// 
	//------------------------------------------------------------------/
	public final java.lang.String
	name()
	{
		return name_;
	}

	//==================================================================/
	//  Contructors and Initialization
	//==================================================================/

	//------------------------------------------------------------------/
	// Atom
	/**
	 * @param   name   the Atom's name
	 */
	// Implementation notes:  
	// 
	//------------------------------------------------------------------/
	public
	Atom( java.lang.String name )
	{
		this.name_ = name;
	}

	//==================================================================/
	//  Converting Terms to term_ts
	//==================================================================/

	//------------------------------------------------------------------/
	// put
	/**
	 * To put an Atom in a term, we put an atom_t into the term_t.
	 * 
	 * @param   var_table  A Hashtable containing term_t's that are
	 * bound to (have packed in) Prolog variables as elements.  The
	 * Elements are keyed by jpl.Variable instances.  Cf. the put()
	 * implementation in the Variable class.
	 * @param   term  A (previously created) term_t which is to be
	 * packed with a Prolog term-type appropriate to the Term type
	 * (e.g., Atom, Variable, Compound, etc.) on which the method is
	 * invoked.)
	 */
	// Implementation notes: 
	// 
	//------------------------------------------------------------------/
	protected final void
	put( Hashtable var_table, term_t term )
	{
		Prolog.put_atom( term, Prolog.new_atom( name_ ) );
	}

	
	//==================================================================/
	//  Converting term_ts to Terms
	//==================================================================/
	
	//------------------------------------------------------------------/
	// from_term_t
	/**
	 * Converts a term_t to an Atom.  Assuming the term is an
	 * atom, we just create a new Atom using the term's name.
	 *
	 * We are careful to create a List.Nil object if indeed the
	 * atom is "[]".  Note that nil is an atom in Prolog and jpl.
	 * 
	 * @param   term     The term_t to convert
	 * @return           A new Atom
	 */
	// Implementation notes:  
	// 
	//------------------------------------------------------------------/
	protected static Term
	from_term_t( Hashtable vars, term_t term )
	{
		StringHolder holder = new StringHolder();
		Prolog.get_atom_chars( term, holder );

		if ( holder.value.equals( "[]" ) ){
			return new List.Nil();
		} else {
			return new Atom( holder.value );
		}
	}

	//==================================================================/
	//  Computing Substitutions
	//==================================================================/


	//------------------------------------------------------------------/
	// computeSubstitution
	/**
	 * Nothing needs to be done if the Term is an Atom.
	 * 
	 * @param   table  table holding Term substitutions, keyed on
	 *                 Variables.
	 */
	// Implementation notes:  
	// 
	//------------------------------------------------------------------/
	protected final void
	computeSubstitution( Hashtable bindings, Hashtable vars )
	{
	}

	
	
	//------------------------------------------------------------------/
	// toString
	/**
	 * Converts an Atom to its String form -- its name.
	 * 
	 * @return  String representation of an Atom
	 */
	// Implementation notes:  
	// 
	//------------------------------------------------------------------/
	public java.lang.String
	toString()
	{
		return name_;
	}
	
	public java.lang.String
	debugString()
	{
		return "(Atom " + toString() + ")";
	}
	
	//------------------------------------------------------------------/
	// equals
	/**
	 * Two Atoms are equal if their names are equal
	 * 
	 * @param   obj  The Object to compare
	 * @return  true if the Object satisfies the above condition
	 */
	// Implementation notes:
	// 
	//------------------------------------------------------------------/
	public final boolean
	equals( Object obj )
	{
		if ( this == obj ){
			return true;
		}
		
		if ( ! (obj instanceof Atom) ){
			return false;
		}
		
		return name_.equals( ((Atom)obj).name_ );
	}
}

//345678901234567890123456789012346578901234567890123456789012345678901234567890