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aka_visitor.hh
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/**
* @file aka_visitor.hh
*
* @author Alejandro M. Aragón <alejandro.aragon@epfl.ch>
*
* @date creation: Fri Jan 04 2013
* @date last modification: Sun Oct 19 2014
*
* @brief Objects that support the visitor design pattern
*
* @section LICENSE
*
* Copyright (©) 2014, 2015 EPFL (Ecole Polytechnique Fédérale de Lausanne)
* Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
*
* Akantu is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation, either version 3 of the License, or (at your option) any
* later version.
*
* Akantu 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 Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Akantu. If not, see <http://www.gnu.org/licenses/>.
*
*/
/* -------------------------------------------------------------------------- */
#ifndef __AKANTU_VISITOR_HH__
#define __AKANTU_VISITOR_HH__
#include "aka_typelist.hh"
namespace akantu {
///////////////////////////////////////////////////////////////////////////
// visitor class template, adapted from the Andrei Alexandrescu's
// "Modern C++ Design"
enum Visit_type { Mutable, Immutable };
template <class T, typename R = void, Visit_type = Mutable>
class StrictVisitor;
template <class T, typename R>
class StrictVisitor<T, R, Mutable>
{
public:
typedef R ReturnType;
typedef T ParamType;
virtual ~StrictVisitor() {}
virtual ReturnType Visit(ParamType&) = 0;
};
template <class T, typename R>
class StrictVisitor<T, R, Immutable>
{
public:
typedef R ReturnType;
typedef const T ParamType;
virtual ~StrictVisitor() {}
virtual ReturnType Visit(ParamType&) = 0;
};
/// class template StrictVisitor (specialization)
template <class Head, class Tail, typename R>
class StrictVisitor<Typelist<Head, Tail>, R, Mutable>
: public StrictVisitor<Head, R, Mutable>, public StrictVisitor<Tail, R, Mutable>
{
public:
typedef R ReturnType;
typedef Head ParamType;
// using StrictVisitor<Head, R>::Visit;
// using StrictVisitor<Tail, R>::Visit;
};
template <class Head, typename R>
class StrictVisitor<Typelist<Head, Null_type>, R, Mutable> : public StrictVisitor<Head, R, Mutable>
{
public:
typedef R ReturnType;
typedef Head ParamType;
using StrictVisitor<Head, R, Mutable>::Visit;
};
template <class Head, class Tail, typename R>
class StrictVisitor<Typelist<Head, Tail>, R, Immutable>
: public StrictVisitor<Head, R, Immutable>, public StrictVisitor<Tail, R, Immutable>
{
public:
typedef R ReturnType;
typedef Head ParamType;
// using StrictVisitor<Head, R>::Visit;
// using StrictVisitor<Tail, R>::Visit;
};
template <class Head, typename R>
class StrictVisitor<Typelist<Head, Null_type>, R, Immutable> : public StrictVisitor<Head, R, Immutable>
{
public:
typedef R ReturnType;
typedef Head ParamType;
using StrictVisitor<Head, R, Immutable>::Visit;
};
////////////////////////////////////////////////////////////////////////////////
// class template NonStrictVisitor
// Implements non-strict visitation (you can implement only part of the Visit
// functions)
//
template <class R>
struct DefaultFunctor {
template <class T>
R operator()(T&) { return R(); }
};
template <class T, typename R = void, Visit_type V = Mutable, class F = DefaultFunctor<R> > class BaseVisitorImpl;
template <class Head, class Tail, typename R, Visit_type V, class F>
class BaseVisitorImpl<Typelist<Head, Tail>, R, V, F>
: public StrictVisitor<Head, R, V>, public BaseVisitorImpl<Tail, R, V, F> {
public:
typedef typename StrictVisitor<Head, R, V>::ParamType ParamType;
virtual R Visit(ParamType& h)
{ return F()(h); }
};
template <class Head, typename R, Visit_type V, class F >
class BaseVisitorImpl<Typelist<Head, Null_type>, R, V, F> : public StrictVisitor<Head, R, V>
{
public:
typedef typename StrictVisitor<Head, R, V>::ParamType ParamType;
virtual R Visit(ParamType& h)
{ return F()(h); }
};
/// Visitor
template <class R>
struct Strict {};
template <typename R, class TList, Visit_type V = Mutable, template <class> class FunctorPolicy = DefaultFunctor>
class Visitor : public BaseVisitorImpl<TList, R, V, FunctorPolicy<R> > {
public:
typedef R ReturnType;
template <class Visited>
ReturnType GenericVisit(Visited& host) {
StrictVisitor<Visited, ReturnType, V>& subObj = *this;
return subObj.Visit(host);
}
};
template <typename R, class TList, Visit_type V>
class Visitor<R, TList, V, Strict> : public StrictVisitor<TList, R, V> {
public:
typedef R ReturnType;
template <class Visited>
ReturnType GenericVisit(Visited& host) {
StrictVisitor<Visited, ReturnType, V>& subObj = *this;
return subObj.Visit(host);
}
};
} // akantu
#endif /* __AKANTU_VISITOR_HH__ */

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