visitable.hpp

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//This file is part of Bertini 2.
//
//visitable.hpp is free software: you can redistribute it and/or modify
//it under the terms of the GNU General Public License as published by
//the Free Software Foundation, either version 3 of the License, or
//(at your option) any later version.
//
//visitable.hpp is distributed in the hope that it will be useful,
//but WITHOUT ANY WARRANTY; without even the implied warranty of
//MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//GNU General Public License for more details.
//
//You should have received a copy of the GNU General Public License
//along with visitable.hpp.  If not, see <http://www.gnu.org/licenses/>.
//
// Copyright(C) 2015 - 2021 by Bertini2 Development Team
//
// See <http://www.gnu.org/licenses/> for a copy of the license, 
// as well as COPYING.  Bertini2 is provided with permitted 
// additional terms in the b2/licenses/ directory.
 
// individual authors of this file include:
// silviana amethyst, university of wisconsin-eau claire
//

 
#ifndef BERTINI_DETAIL_VISITABLE_HPP
#define BERTINI_DETAIL_VISITABLE_HPP
 
#include "bertini2/detail/visitor.hpp"
#include "bertini2/detail/events.hpp"
 
namespace bertini{
 
    namespace policy{

        template<class VisitedT, typename RetT>
        struct DefaultConstruct
        {
            static RetT OnUnknownVisitor(VisitedT&a, VisitorBase&) // VisitorBase is inherited from using CRTP -- it's not a template parameter to this function, so its typeid name is useless.
            {
                std::cout << "unknown visitor: " << a << " of type " << typeid(VisitedT).name() << ".  Make sure you've added it in all three places!  two in the class definition (type inheritance listing as visiting, and virtual function declaration), and one in cpp source (function definition)." << std::endl;
                return VisitedT();
            }
        };
 
        template<class VisitedT, typename RetT>
        struct RaiseExceptionWithTypeNamesInMessage
        {
            static RetT OnUnknownVisitor(VisitedT&a, VisitorBase&)
            {
                std::stringstream err_msg;
                err_msg << "unknown visitor: " << a << " of type " << typeid(VisitedT).name() << ".  Make sure you've added it in all three places!  two in the class definition (type inheritance listing as visiting, and virtual function declaration), and one in cpp source (function definition)." << std::endl;
                throw std::runtime_error(err_msg.str());
            }
        };
        template<class VisitedT, typename RetT>
        using DefaultCatchAll = RaiseExceptionWithTypeNamesInMessage<VisitedT, RetT>;
    } // namespace policy
 
    
 

    template< typename RetT = void, template<class,class> class CatchAll = policy::DefaultCatchAll>
    class VisitableBase
    {
    public:
        typedef RetT VisitReturnType;
        virtual ~VisitableBase() = default;
        virtual VisitReturnType Accept(VisitorBase&) = 0; // the implementation will either be provided by a macro, or by hand, for each class which is visitable.
 
    protected:

        template<typename T>
        static
        VisitReturnType AcceptBase(T& visited, VisitorBase& guest)
        {
            if (auto p = dynamic_cast<Visitor<T>*>(&guest))
                return p->Visit(visited);
            else
                return CatchAll<T,RetT>::OnUnknownVisitor(visited, guest);
        }
    };
 
    
    #define BERTINI_DEFAULT_VISITABLE() \
        virtual VisitReturnType Accept(VisitorBase& guest) override \
        { return AcceptBase(*this, guest); }
 
} // namespace bertini
 
 
#endif