/* 
 * Kodkod -- Copyright (c) 2005-present, Emina Torlak
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package kodkod.ast;


import kodkod.ast.visitor.ReturnVisitor;
import kodkod.ast.visitor.VoidVisitor;


/**
 * Negation of a {@link kodkod.ast.Formula formula}.
 * 
 * @specfield formula: Formula
 * @invariant children = 0->formula
 * @author Emina Torlak
 */
public final class NotFormula extends Formula {
    private final Formula formula;
    
    /**
     * Constructs a new formula: !formula 
     * 
     * @ensures this.formula' = formula
     * @throws NullPointerException  formula = null
     */
    NotFormula(Formula child) {
        if (child == null) throw new NullPointerException("formula");
        this.formula = child;
    }
 
    /**
     * Returns this.formula.
     * @return this.formula
     */
    public Formula formula() { return formula; }
    
    /**
     * {@inheritDoc}
     * @see kodkod.ast.Formula#accept(kodkod.ast.visitor.ReturnVisitor)
     */
     public <E, F, D, I> F accept(ReturnVisitor<E, F, D, I> visitor) {
         return visitor.visit(this);
     }
     
     /**
      * {@inheritDoc}
      * @see kodkod.ast.Node#accept(kodkod.ast.visitor.VoidVisitor)
      */
     public void accept(VoidVisitor visitor) {
         visitor.visit(this);
     }
     
     /**
      * {@inheritDoc}
      * @see kodkod.ast.Node#toString()
      */
    public String toString() {
        return "!" + formula;
    }
}