Visitor.hpp

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/*
    Copyright (C) 2014-2016 Leosac
 
    This file is part of Leosac.
 
    Leosac is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    Leosac 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 Affero General Public License for more details.
 
    You should have received a copy of the GNU Affero General Public License
    along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
 
#pragma once
 
#include <type_traits>
 
namespace Leosac
{
namespace Tools
{
 
class IVisitable;
 
class BaseVisitor
{
  public:
    virtual ~BaseVisitor() = default;
 
    virtual void cannot_visit(const IVisitable &);
};
 
class IVisitable;
 
template <typename T>
class Visitor : public virtual BaseVisitor
{
  public:
    using VisitableT = std::remove_reference_t<std::remove_const_t<T>>;
 
    // While correct, this forces additional includes.
    // static_assert(std::is_base_of<IVisitable, VisitableT>::value,
    //             "Trying to implement a visitor for a type that doesn't implement "
    //           "IVisitable.");
 
    virtual void visit(const VisitableT &)
    {
    }
    virtual void visit(VisitableT &visitable)
    {
        visit(const_cast<const VisitableT &>(visitable));
    }
};
}
}