content: /* 
   * 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;
      }
  }
  