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/** \file enumerator_transform.h */ // -*-c++-*-
// Copyright (C) 2010 Daniel Burrows
//
// This program 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 2 of the
// License, or (at your option) any later version.
//
// This program 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 this program; see the file COPYING. If not, write to
// the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
// Boston, MA 02111-1307, USA.
#ifndef ENUMERATOR_TRANSFORM_H
#define ENUMERATOR_TRANSFORM_H
#include "enumerator.h"
#include <boost/function.hpp>
#include <boost/make_shared.hpp>
namespace aptitude
{
namespace util
{
/** \brief An enumerator that applies a function argument to each
* element returned by another enumerator.
*
* \tparam From The original type stored in the enumeration.
* \tparam To The type of value returned by this enumeration.
*/
template<typename From, typename To>
class enumerator_transform : public enumerator<To>
{
const boost::shared_ptr<enumerator<From> > sub_enumerator;
const boost::function<To (From)> f;
public:
/** \warning Should only be used by create(). */
enumerator_transform(const boost::shared_ptr<enumerator<From> > &
_sub_enumerator,
const boost::function<To (From)> &_f);
/** \brief Create an enumerator_transform.
*
* \param sub_enumerator The enumerator that is to be transformed.
* \param f The function to apply to each element of
* _sub_enumerator. Normally this should
* not have side-effects.
*/
static boost::shared_ptr<enumerator_transform>
create(const boost::shared_ptr<enumerator<From> > &sub_enumerator,
const boost::function<To (From)> &f);
bool advance();
To get_current();
};
template<typename From, typename To>
enumerator_transform<From, To>::enumerator_transform(const boost::shared_ptr<enumerator<From> > &_sub_enumerator,
const boost::function<To (From)> &_f)
: sub_enumerator(_sub_enumerator),
f(_f)
{
}
template<typename From, typename To>
boost::shared_ptr<enumerator_transform<From, To> >
enumerator_transform<From, To>::create(const boost::shared_ptr<enumerator<From> > &sub_enumerator,
const boost::function<To (From)> &f)
{
return boost::make_shared<enumerator_transform<From, To> >(sub_enumerator, f);
}
template<typename From, typename To>
bool enumerator_transform<From, To>::advance()
{
return sub_enumerator->advance();
}
template<typename From, typename To>
To enumerator_transform<From, To>::get_current()
{
return f(sub_enumerator->get_current());
}
}
}
#endif // ENUMERATOR_TRANSFORM_H
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