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 variable declaration, such as 'x : lone X'.  Declarations
   * are used with quantified formulas and comprehension expressions.
   * 
   * @specfield variable: Variable
   * @specfield expression: Expression
   * @specfield multiplicity: LONE + ONE + SOME + SET
   * @invariant variable.arity = expression.arity
   * @invariant children = 0->variable + 1->expression
   * @author Emina Torlak 
   */
  public final class Decl extends Decls {
  	
      private final Variable variable;
      private final Multiplicity mult;
      private final Expression expression;
      
      /**  
       * Constructs a new declaration from the specified variable and
       * expression, with the specified order.
       * 
       * @ensures this.variable' = variable && this.expression' = expression && this.multiplicity' = mult
       * @throws NullPointerException  variable = null || expression = null || mult = null
       * @throws IllegalArgumentException  variable.arity != expression.arity 
       */
      Decl(Variable variable, Multiplicity mult, Expression expression) {
     		if (mult==Multiplicity.NO)
      			throw new IllegalArgumentException("NO is not a valid multiplicity in a declaration.");
          if (variable.arity() != expression.arity())
              throw new IllegalArgumentException("Unmatched arities in a declaration: " + variable + " and " + expression);
          if (mult != Multiplicity.SET && expression.arity()>1) 
          		throw new IllegalArgumentException("Cannot use multiplicity " + mult + " with an expression of arity > 1.");
          this.variable = variable;
          this.mult = mult;
          this.expression = expression;
      }
      
      /**
       * Returns the variable in this declaration.
       * @return this.variable
       */
      public Variable variable() { return variable; }
      
      /**
       * Returns the multiplicity in this declaration.
       * @return this.multiplicity
       */
      public Multiplicity multiplicity() { return mult; }
      
      /**
       * Returns the expression in this declaration.
       * @return this.exresssion
       */
      public Expression expression() { return expression;  }
      
      /**
       * {@inheritDoc}
       * @see kodkod.ast.Node#accept(kodkod.ast.visitor.ReturnVisitor)
       */
      public <E, F, D, I> D 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 variable + ": " + mult + " " + expression; }
     
  }
  