/*
* Negation.java
*
* Copyright (C) 2008 Pei Wang
*
* This file is part of Open-NARS.
*
* Open-NARS is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* Open-NARS 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Open-NARS. If not, see <http://www.gnu.org/licenses/>.
*/
package nars.language;
import nars.io.Symbols.NativeOperator;
/**
* A negation of a statement.
*/
public class Negation extends CompoundTerm {
/** avoid using this externally, because double-negatives can be unwrapped to the
* original term using Negation.make */
protected Negation(final Term t) {
super(new Term[] { t });
init(term);
}
@Override
protected CharSequence makeName() {
return makeCompoundName(NativeOperator.NEGATION, term[0]);
}
@Override
public int getMinimumRequiredComponents() {
return 1;
}
/**
* Clone an object
*
* @return A new object
*/
@Override
public Negation clone() {
return new Negation(term[0]);
}
@Override
public Term clone(final Term[] replaced) {
if (replaced.length!=1)
return null;
return make(replaced[0]);
}
/**
* Try to make a Negation of one component. Called by the inference rules.
*
* @param t The component
* @param memory Reference to the memory
* @return A compound generated or a term it reduced to
*/
public static Term make(final Term t) {
if (t instanceof Negation) {
// (--,(--,P)) = P
return ((Negation) t).term[0];
}
return new Negation(t);
}
/**
* Try to make a new Negation. Called by StringParser.
*
* @return the Term generated from the arguments
* @param argument The list of term
* @param memory Reference to the memory
*/
public static Term make(final Term[] argument) {
if (argument.length != 1)
return null;
return make(argument[0]);
}
/**
* Get the operator of the term.
*
* @return the operator of the term
*/
@Override
public NativeOperator operator() {
return NativeOperator.NEGATION;
}
public static boolean areMutuallyInverse(Term tc, Term ptc) {
//doesnt seem necessary to check both, one seems sufficient.
//incurs cost of creating a Negation and its id
return (ptc.equals(Negation.make(tc)) /* || tc.equals(Negation.make(ptc))*/ );
}
}