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// ============================================================================
// $Id: UnaryNegate.java,v 1.14 2006/08/07 03:56:27 davidahall Exp $
// Copyright (c) 2002-2005  David A. Hall
// ============================================================================
// The contents of this file are subject to the Common Development and
// Distribution License (CDDL), Version 1.0 (the License); you may not use this 
// file except in compliance with the License.  You should have received a copy
// of the the License along with this file: if not, a copy of the License is 
// available from Sun Microsystems, Inc.
//
// http://www.sun.com/cddl/cddl.html
//
// From time to time, the license steward (initially Sun Microsystems, Inc.) may
// publish revised and/or new versions of the License.  You may not use,  
// distribute, or otherwise make this file available under subsequent versions 
// of the License.
// 
// Alternatively, the contents of this file may be used under the terms of the 
// GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
// case the provisions of the LGPL are applicable instead of those above. If you 
// wish to allow use of your version of this file only under the terms of the 
// LGPL, and not to allow others to use your version of this file under the 
// terms of the CDDL, indicate your decision by deleting the provisions above 
// and replace them with the notice and other provisions required by the LGPL. 
// If you do not delete the provisions above, a recipient may use your version 
// of this file under the terms of either the CDDL or the LGPL.
// 
// 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. 
// ============================================================================

package net.sf.jga.fn.logical;

import net.sf.jga.fn.UnaryPredicate;
import net.sf.jga.fn.UnaryFunctor;

/**
 * Unary Predicate that logically negates the result of a child predicate.
 * Returns true when child predicate <b>p</b> returns false given object
 * argument <b>x</b>.
 * <p>
 * Copyright &copy; 2002-2005  David A. Hall
 *
 * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
 **/

public class UnaryNegate<T> extends UnaryPredicate<T> {

    static final long serialVersionUID = -722445812960547108L;
    
    private UnaryFunctor<? super T, Boolean> _p;
    
    /**
     * Builds a UnaryNegate predicate wrapping the given Unary Predicate.
     * @throws IllegalArgumentException when no child predicate is given 
     */
    public UnaryNegate(UnaryFunctor<? super T, Boolean> p) {
        if (p == null) {
            throw new IllegalArgumentException("Child Predicate may not be null");
        }
        
        _p = p;
    }

    /**
     * Returns the child predicate.
     * @return the child predicate.
     */
    public UnaryFunctor<? super T,Boolean> getPredicate() { return _p; }

    // UnaryPredicate interface
    
    /**
     * Given argument <b>x</b>, returns true when child
     * predicate <b>p</b> returns false for x, otherwise returns true.
     * 
     * @return !(p.p(x))
     */
    public Boolean fn(T x) {
        return ! _p.fn(x);
    }
    
    /**
     * Calls the Visitor's <code>visit(UnaryNegate)</code> method, if it
     * implements the nested Visitor interface.
     */
    public void accept(net.sf.jga.fn.Visitor v) {
        if (v instanceof UnaryNegate.Visitor)
            ((UnaryNegate.Visitor)v).visit(this);
        else
            v.visit(this);
    }

    // Object overrides

    public String toString() {
        return "UnaryNegate";
    }
    
    // Acyclic Visitor
    
    /**
     * Interface for classes that may interpret a <b>UnaryNegate</b>
     * predicate.
     */
    public interface Visitor extends net.sf.jga.fn.Visitor {
        public void visit(UnaryNegate host);
    }
}
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