jpl

Class Atom

java.lang.Object

jpl.Term

jpl.Atom

Direct Known Subclasses:

List.Nil

public class Atom
extends Term

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.

Version:

$Revision: 1.1.1.1 $

Author:

Fred Dushin

See Also:

Term, Compound

Field Summary

Fields

Modifier and Type	Field and Description
protected String	name_ This atom's name

Constructor Summary

Constructors

Constructor and Description
Atom(String name)

Method Summary

Modifier and Type	Method and Description
protected void	computeSubstitution(Hashtable bindings, Hashtable vars) Nothing needs to be done if the Term is an Atom.
String	debugString()
boolean	equals(Object obj) Two Atoms are equal if their names are equal
protected static Term	from_term_t(Hashtable vars, term_t term) Converts a term_t to an Atom.
String	name()
protected void	put(Hashtable var_table, term_t term) To put an Atom in a term, we put an atom_t into the term_t.
String	toString() Converts an Atom to its String form -- its name.

Methods inherited from class jpl.Term

computeSubstitutions, debugString, from_term_t, terms_equals, terms_to_term_ts, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

name_

protected String name_

This atom's name

Constructor Detail

Atom

public Atom(String name)

Parameters:

name - the Atom's name

Method Detail

name

public final String name()

Returns:

the name of the Atom

put

protected final void put(Hashtable var_table,
                         term_t term)

To put an Atom in a term, we put an atom_t into the term_t.

Specified by:

put in class Term

Parameters:

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.

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.)

from_term_t

protected static Term from_term_t(Hashtable vars,
                                  term_t term)

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.

Parameters:

term - The term_t to convert

Returns:

A new Atom

computeSubstitution

protected final void computeSubstitution(Hashtable bindings,
                                         Hashtable vars)

Nothing needs to be done if the Term is an Atom.

Specified by:

computeSubstitution in class Term

Parameters:

table - table holding Term substitutions, keyed on Variables.

toString

public String toString()

Converts an Atom to its String form -- its name.

Overrides:

toString in class Object

Returns:

String representation of an Atom

debugString

public String debugString()

Specified by:

debugString in class Term

equals

public final boolean equals(Object obj)

Two Atoms are equal if their names are equal

Overrides:

equals in class Object

Parameters:

obj - The Object to compare

Returns:

true if the Object satisfies the above condition