text: //=================================================================================================
  /*!
  //  \file blaze/math/traits/DeclSymExprTrait.h
  //  \brief Header file for the DeclSymExprTrait class template
  //
  //  Copyright (C) 2013 Klaus Iglberger - All Rights Reserved
  //
  //  This file is part of the Blaze library. You can redistribute it and/or modify it under
  //  the terms of the New (Revised) BSD License. Redistribution and use in source and binary
  //  forms, with or without modification, are permitted provided that the following conditions
  //  are met:
  //
  //  1. Redistributions of source code must retain the above copyright notice, this list of
  //     conditions and the following disclaimer.
  //  2. Redistributions in binary form must reproduce the above copyright notice, this list
  //     of conditions and the following disclaimer in the documentation and/or other materials
  //     provided with the distribution.
  //  3. Neither the names of the Blaze development group nor the names of its contributors
  //     may be used to endorse or promote products derived from this software without specific
  //     prior written permission.
  //
  //  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
  //  EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  //  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
  //  SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  //  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
  //  TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  //  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  //  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  //  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  //  DAMAGE.
  */
  //=================================================================================================
  
  #ifndef _BLAZE_MATH_TRAITS_DECLSYMEXPRTRAIT_H_
  #define _BLAZE_MATH_TRAITS_DECLSYMEXPRTRAIT_H_
  
  
  //*************************************************************************************************
  // Includes
  //*************************************************************************************************
  
  #include <utility>
  #include <blaze/math/typetraits/IsMatrix.h>
  #include <blaze/util/InvalidType.h>
  #include <blaze/util/mpl/If.h>
  #include <blaze/util/typetraits/RemoveReference.h>
  
  
  namespace blaze {
  
  //=================================================================================================
  //
  //  CLASS DEFINITION
  //
  //=================================================================================================
  
  //*************************************************************************************************
  /*!\brief Evaluation of the return type of a symmetry declaration (declsym) expression.
  // \ingroup math_traits
  //
  // Via this type trait it is possible to evaluate the return type of a symmetry declaration
  // (declsym) expression. Given the type \a T, which must be a matrix type, the nested type
  // \a Type corresponds to the resulting return type. In case the type of \a T doesn't fit or
  // if no declsym operation exists for the type, the resulting data type \a Type is set to
  // \a INVALID_TYPE.
  */
  template< typename T >  // Type of the declsym operand
  struct DeclSymExprTrait
  {
   private:
     //**struct Failure******************************************************************************
     /*! \cond BLAZE_INTERNAL */
     struct Failure { using Type = INVALID_TYPE; };
     /*! \endcond */
     //**********************************************************************************************
  
     //**struct Result*******************************************************************************
     /*! \cond BLAZE_INTERNAL */
     struct Result { using Type = decltype( declsym( std::declval<T>() ) ); };
     /*! \endcond */
     //**********************************************************************************************
  
   public:
     //**********************************************************************************************
     /*! \cond BLAZE_INTERNAL */
     using Type = typename If_< IsMatrix< RemoveReference_<T> >
                              , Result
                              , Failure >::Type;
     /*! \endcond */
     //**********************************************************************************************
  };
  //*************************************************************************************************
  
  
  //*************************************************************************************************
  /*!\brief Auxiliary alias declaration for the DeclSymExprTrait class template.
  // \ingroup math_traits
  //
  // The DeclSymExprTrait_ alias declaration provides a convenient shortcut to access the nested
  // \a Type of the DeclSymExprTrait class template. For instance, given the type \a T the following
  // two type definitions are identical:
  
     \code
     using Type1 = typename DeclSymExprTrait<T>::Type;
     using Type2 = DeclSymExprTrait_<T>;
     \endcode
  */
  template< typename T >  // Type of the declsym operand
  using DeclSymExprTrait_ = typename DeclSymExprTrait<T>::Type;
  //*************************************************************************************************
  
  } // namespace blaze
  
  #endif
  