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.operator.Multiplicity;
  import kodkod.ast.visitor.ReturnVisitor;
  import kodkod.ast.visitor.VoidVisitor;
  
  
  
  /** 
   * A comprehension expression, e.g. { a: A, b: B | a.r = b }
   *  
   * @specfield decls: Declarations
   * @specfield formula: Formula
   * @invariant arity = sum(decls.declarations().arity)
   * @invariant children = 0->decls + 1->formula
   * @author Emina Torlak 
   */
  public final class Comprehension extends Expression  {
  
      private final Decls decls;
      private final Formula formula;
  
      
      /**  
       * Constructs a comprehension expression with the specified decls
       * and formula
       * 
       * @ensures this.decls' = decls && this.formula' = formula
       * @throws NullPointerException  decls = null || formula = null
       */
      Comprehension(Decls declarations, Formula formula) {
          if (formula == null) throw new NullPointerException("null formula");
          for(Decl decl : declarations) { 
          	if (decl.variable().arity()>1 || decl.multiplicity()!=Multiplicity.ONE)
          		throw new IllegalArgumentException("Cannot have a higher order declaration in a comprehension: "+decl);
          }
          this.decls = declarations;
          this.formula = formula;
      }
  
      /**
       * @return this.formula
       */
      public Formula formula() {return formula; }
      
      /**
       * @return this.decls
       */
      public Decls decls() {return decls;}
      
      /**
       * Returns the arity of this comprehension expression, which is the sum
       * of the arities of declared variables
       * 
       * @return #this.decls
       */
      public int arity() {
          return decls.size();
      }
      
     /**
      * {@inheritDoc}
      * @see kodkod.ast.Expression#accept(kodkod.ast.visitor.ReturnVisitor)
      */
      public <E, F, D, I> E 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 "{ " + decls().toString() + " | " + formula().toString() + " }";
      }
  
  }
  