class.h

// Description: Class wrapping

#ifndef PASTELSYS_CLASS_H
#define PASTELSYS_CLASS_H

#include <type_traits>

namespace Pastel
{

    //! A tagged class-wrapper using membership.
    /*!
   Preconditions:
   !std::is_class<Type>::value

   Type != void:
   The wrapper class contains a member of the given 
   Type, and is implicitly convertible to a (const/non-const)
   reference to that member. In addition, the 
   wrapper has a constructor which accepts an
   initializer of type Type. This way the wrapper
   acts as transparently as possible to make it
   possible to inherit from a native type.

   Type == void:
   The result is an empty class, with trivial comparison 
   operators, and a trivial hash function. This is useful 
   for empty base-class optimization.
   */
    template <
        typename Type, 
        typename Tag = void>
    class Member_Class;

    //! A tagged class-wrapper using inheritance.
    /*!
   Preconditions:
   std::is_class<Type>::value

   The Type is made a base-class of the Inherited_Class.
   Constructors are perfectly forwarded to Type.
   */
    template <
        typename Type, 
        typename Tag = void>
    class Inherited_Class;

    //! Wraps class -> Inherited_Class, non-class -> Member_Class.
    template <
        typename Type,
        typename Tag = void>
    struct Class_F
    : std::conditional<
        std::is_class<Type>::value,
        Inherited_Class<Type, Tag>,
        Member_Class<Type, Tag>
    >
    {};

    template <
        typename Type,
        typename Tag = void>
    using Class = 
        typename Class_F<Type, Tag>::type;

}

#include "pastel/sys/generic/class.hpp"

#endif