// $Id$ 
// $Source$ 
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// 
//                           Sacado Package
//                 Copyright (2006) Sandia Corporation
// 
// Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
// the U.S. Government retains certain rights in this software.
// 
// This library is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as
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// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
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// Questions? Contact David M. Gay (dmgay@sandia.gov) or Eric T. Phipps
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#ifndef SACADO_ELRCACHEFAD_GENERALFADEXPR_HPP
#define SACADO_ELRCACHEFAD_GENERALFADEXPR_HPP

#include "Sacado_ELRCacheFad_GeneralFad.hpp"

namespace Sacado {

  namespace ELRCacheFad {

    //! GeneralFad expression template specialization
    /*!
     * This template class represents a simple GeneralFad expression and
     * mixes-in the GeneralFad interface and the expression template
     * interface using the caching expression-level-revese-mode 
     * expression templates.
     */
    template <typename T, typename Storage> 
    class Expr< GeneralFad<T,Storage> > : public GeneralFad<T,Storage> {

    public:

      typedef typename GeneralFad<T,Storage>::value_type value_type;
      typedef typename GeneralFad<T,Storage>::scalar_type scalar_type;

      //! Typename of base-expressions
      typedef GeneralFad<T,Storage> base_expr_type;

      //! Number of arguments
      static const int num_args = 1;

      //! Is expression linear
      static const bool is_linear = true;

      //! Default constructor
      Expr() : 
	GeneralFad<T,Storage>() {}

      //! Constructor with supplied value \c x
      /*!
       * Initializes value to \c x and derivative array is empty
       */
      Expr(const T & x) : 
	GeneralFad<T,Storage>(x) {}

      //! Constructor with size \c sz and value \c x
      /*!
       * Initializes value to \c x and derivative array 0 of length \c sz
       */
      Expr(const int sz, const T & x) : 
	GeneralFad<T,Storage>(sz,x) {}

      //! Constructor with size \c sz, index \c i, and value \c x
      /*!
       * Initializes value to \c x and derivative array of length \c sz
       * as row \c i of the identity matrix, i.e., sets derivative component
       * \c i to 1 and all other's to zero.
       */
      Expr(const int sz, const int i, const T & x) : 
	GeneralFad<T,Storage>(sz,i,x) {}

      //! Copy constructor
      Expr(const Expr& x) : 
	GeneralFad<T,Storage>(static_cast<const GeneralFad<T,Storage>&>(x)) {}

      //! Copy constructor from any Expression object
      template <typename S> Expr(const Expr<S>& x) :
	GeneralFad<T,Storage>(x) {}

      //! Destructor
      ~Expr() {}

      //! Return partials w.r.t. arguments
      void computePartials(const T& bar, T partials[]) const { 
	partials[0] = bar; 
      }

      //! Return tangent component \c i of arguments
      void getTangents(int i, T dots[]) const { 
	if (i<this->size())
	  dots[0] = this->fastAccessDx(i);
	else
	  dots[0] = 0.0;
      }

      //! Return whether argument is active
      template <int Arg>
      bool isActive() const { return this->size() > 0; }

      //! Return whether expression is linear
      bool isLinear() const { return true; }

      //! Return tangent component \c i of argument \c Arg
      template <int Arg>
      T getTangent(int i) const { return this->fastAccessDx(i); }

      const base_expr_type& getArg(int j) const { return *this; }

    }; // class Expr<GeneralFad>
    
    //! Specialization of %ExprPromote to GeneralFad types
    template <typename T, typename S>
    struct ExprPromote< GeneralFad<T,S>, 
			typename GeneralFad<T,S>::value_type > {
      typedef GeneralFad<T,S> type;
    };
    
    //! Specialization of %ExprPromote to GeneralFad types
    template <typename T, typename S>
    struct ExprPromote< typename GeneralFad<T,S>::value_type, 
			GeneralFad<T,S> > {
      typedef GeneralFad<T,S> type;
    };

    //! Specialization of %ExprPromote to GeneralFad types
    template <typename T, typename S>
    struct ExprPromote< GeneralFad<T,S>, 
			typename dummy<typename GeneralFad<T,S>::value_type,
				       typename GeneralFad<T,S>::scalar_type
				       >::type > {
      typedef GeneralFad<T,S> type;
    };
    
    //! Specialization of %ExprPromote to GeneralFad types
    template <typename T, typename S>
    struct ExprPromote< typename dummy<typename GeneralFad<T,S>::value_type,
				       typename GeneralFad<T,S>::scalar_type
				       >::type, 
			GeneralFad<T,S> > {
      typedef GeneralFad<T,S> type;
    };

  } // namespace ELRCacheFad

} // namespace Sacado

#include "Sacado_ELRCacheFad_Ops.hpp"

#endif // SACADO_ELRCACHEFAD_GENERALFADEXPR_HPP
