Sacado_Fad_Expression.hpp

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// @HEADER
// *****************************************************************************
//                           Sacado Package
//
// Copyright 2006 NTESS and the Sacado contributors.
// SPDX-License-Identifier: LGPL-2.1-or-later
//
// ***********************************************************************
//
// The forward-mode AD classes in Sacado are a derivative work of the
// expression template classes in the Fad package by Nicolas Di Cesare.
// The following banner is included in the original Fad source code:
//
// ************ DO NOT REMOVE THIS BANNER ****************
//
//  Nicolas Di Cesare <Nicolas.Dicesare@ann.jussieu.fr>
//  http://www.ann.jussieu.fr/~dicesare
//
//            CEMRACS 98 : C++ courses,
//         templates : new C++ techniques
//            for scientific computing
//
//********************************************************
//
//  A short implementation ( not all operators and
//  functions are overloaded ) of 1st order Automatic
//  Differentiation in forward mode (FAD) using
//  EXPRESSION TEMPLATES.
//
//********************************************************
// @HEADER

#ifndef SACADO_FAD_EXPRESSION_HPP
#define SACADO_FAD_EXPRESSION_HPP

#include "Sacado_Traits.hpp"
#include "Sacado_Fad_ExpressionFwd.hpp"

namespace Sacado {

  namespace Fad {


    template <typename> struct BaseExpr {};

    struct ExprSpecDefault {};
    template <typename ExprT> struct ExprSpec {
      typedef ExprSpecDefault type;
    };


    template <typename ExprT, typename Spec>
    class Expr {
    public:
      typedef ExprT value_type;
    };

    template <typename ExprT, typename Spec>
    struct ExprSpec< Expr<ExprT,Spec> > {
      typedef Spec type;
    };


    template <typename T>
    struct ExprLevel {
      static const unsigned value = 0;
    };

    template <typename T>
    struct ExprLevel< Expr<T> > {
      static const unsigned value =
        ExprLevel< typename Expr<T>::value_type >::value + 1;
    };

    template <typename T>
    struct IsFadExpr {
      static const bool value = false;
    };

    template <typename T>
    struct IsFadExpr< Expr<T> > {
      static const bool value = true;
    };


    template <typename ConstT>
    class ConstExpr {

    public:

      typedef ConstT value_type;

      typedef typename ScalarType<value_type>::type scalar_type;

      typedef ConstT base_expr_type;

      SACADO_INLINE_FUNCTION
      ConstExpr(const ConstT& constant) : constant_(constant) {}

      SACADO_INLINE_FUNCTION
      const ConstT& val() const { return constant_; }

      SACADO_INLINE_FUNCTION
      const ConstT& val(int j) const { return constant_; }

    protected:

      const ConstT& constant_;

    }; // class ConstExpr

  } // namespace Fad

  template <typename T>
  struct IsExpr< Fad::Expr<T> > {
    static const bool value = true;
  };

  template <typename T>
  struct BaseExprType< Fad::Expr<T> > {
    typedef typename Fad::Expr<T>::base_expr_type type;
  };

  template <typename T>
  struct ValueType< Fad::ConstExpr<T> > {
    typedef typename Fad::ConstExpr<T>::value_type type;
  };

} // namespace Sacado

#include "Sacado_SFINAE_Macros.hpp"

#endif // SACADO_FAD_EXPRESSION_HPP