code: ///////////////////////////////////////////////////////////////////////////
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  //                  / /   ____  ____ _(_)____/ | / / ____/               //
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  //                                                                       //
  //               The Next Generation Logic Library                       //
  //                                                                       //
  ///////////////////////////////////////////////////////////////////////////
  //                                                                       //
  //  Copyright 2015-20xx Christoph Zengler                                //
  //                                                                       //
  //  Licensed under the Apache License, Version 2.0 (the "License");      //
  //  you may not use this file except in compliance with the License.     //
  //  You may obtain a copy of the License at                              //
  //                                                                       //
  //  http://www.apache.org/licenses/LICENSE-2.0                           //
  //                                                                       //
  //  Unless required by applicable law or agreed to in writing, software  //
  //  distributed under the License is distributed on an "AS IS" BASIS,    //
  //  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or      //
  //  implied.  See the License for the specific language governing        //
  //  permissions and limitations under the License.                       //
  //                                                                       //
  ///////////////////////////////////////////////////////////////////////////
  
  package org.logicng.knowledgecompilation.dnnf.datastructures;
  
  import org.logicng.formulas.Formula;
  import org.logicng.formulas.Variable;
  import org.logicng.knowledgecompilation.dnnf.functions.DnnfFunction;
  
  import java.util.SortedSet;
  
  /**
   * A DNNF - Decomposable Negation Normal Form.
   * @version 2.0.0
   * @since 2.0.0
   */
  public final class Dnnf {
  
      private final SortedSet<Variable> originalVariables;
      private final Formula formula;
  
      /**
       * Constructs a new DNNF.
       * @param originalVariables the set of original variables
       * @param dnnf              the formula of the DNNF
       */
      public Dnnf(final SortedSet<Variable> originalVariables, final Formula dnnf) {
          this.originalVariables = originalVariables;
          this.formula = dnnf;
      }
  
      /**
       * Executes a given DNNF function on this DNNF.
       * @param function the function
       * @param <RESULT> the result type
       * @return the result of the function application
       */
      public <RESULT> RESULT execute(final DnnfFunction<RESULT> function) {
          return function.apply(this.originalVariables, this.formula);
      }
  
      /**
       * Returns the formula of the DNNF.
       * @return the formula
       */
      public Formula formula() {
          return this.formula;
      }
  
      /**
       * Returns the original variables of the formula
       * @return the original variables
       */
      public SortedSet<Variable> getOriginalVariables() {
          return this.originalVariables;
      }
  }
  