Visit.h

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//=========================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//=========================================================================
#ifndef smtk_common_Visit_h
#define smtk_common_Visit_h
 
#include <type_traits>
#include <utility>
 
namespace smtk
{
namespace common
{
 
enum class Visit
{
  Continue, 
  Halt      
};
 
enum class Visited
{
  All,  
  Some, 
  Empty 
};
 
template<typename Functor>
struct VisitorFunctor
{
  VisitorFunctor(Functor f)
    : m_functor(f)
  {
  }
 
  template<class... Types>
  auto invokeVisitor(Types&&... args) const -> typename std::
    enable_if<std::is_same<decltype(std::declval<Functor>()(args...)), Visit>::value, Visit>::type
  {
    return m_functor(std::forward<Types>(args)...);
  }
 
  template<class... Types>
  auto invokeVisitor(Types&&... args) const -> typename std::
    enable_if<!std::is_same<decltype(std::declval<Functor>()(args...)), Visit>::value, Visit>::type
  {
    m_functor(std::forward<Types>(args)...);
    return Visit::Continue;
  }
 
  template<class... Types>
  Visit operator()(Types&&... args) const
  {
    return this->invokeVisitor(std::forward<Types>(args)...);
  }
 
  Functor m_functor;
};
 
} // namespace common
} // namespace smtk
 
#endif // smtk_common_Visit_h