/usr/include/CGAL/Flattening_iterator.h is in libcgal-dev 4.2-5ubuntu1.
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// All rights reserved.
//
// This file is part of CGAL (www.cgal.org); 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.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL$
// $Id$
//
// Author(s) : Arno Eigenwillig <arno@mpi-inf.mpg.de>
#ifndef CGAL_FLATTENING_ITERATOR_H
#define CGAL_FLATTENING_ITERATOR_H 1
#include <CGAL/basic.h>
#include <CGAL/Nested_iterator.h>
#include <iterator>
#include <functional>
// LiS2CGAL check whether Nested_iterator in CGAL works in STL_extensions
namespace CGAL {
/*! Suppose you have an iterator range and suppose further that
* the values in that iterator range are containers and thus
* define iterator ranges themselves (accessible through
* some \c begin and \c end functions).
* \e Flattening the iterator range means to turn it into one
* iterator range whose values are the values of the containers
* in the original range.
* For example, a range of lists (1,2),(3),(4,5,6) can be
* flattened into a range 1,2,3,4,5,6
*
* The class templates \c Flattening_iterator and
* \c Flattening_const_iterator implement this flattening.
* So far, only the \c const version has been implemented,
* i.e. the values in the flattened range are read-only.
*
* But what about an iterator range whose values are lists of
* vectors of vectors of ... and so on?
* Yes, it is possible to flatten such nested containers, too,
* by recursive application of \c Flattening*_iterator.
* The class templates \c Recursive_flattening and
* \c Recursive_const_flattening offer the necessary
* typedefs and conversions.
* So far, only the \c const version has been implemented.
*/
template <int level_, class InputIterator>
class Recursive_const_flattening;
template <class InputIterator>
class Recursive_const_flattening<0, InputIterator> {
public:
typedef Recursive_const_flattening Self;
static const int level = 0;
typedef InputIterator Input_iterator;
typedef Input_iterator Recursive_flattening_iterator;
struct Flatten {
typedef Recursive_flattening_iterator result_type;
typedef Input_iterator argument_type;
Recursive_flattening_iterator
operator () (Input_iterator /*end*/, Input_iterator it) {
return it;
}
};
};
template <class InputIterator>
class Recursive_const_flattening<1, InputIterator> {
public:
typedef Recursive_const_flattening Self;
static const int level = 1;
typedef InputIterator Input_iterator;
private:
struct Nested_iterator_traits
{
typedef Input_iterator Base_iterator;
typedef typename std::iterator_traits<Input_iterator>::value_type::const_iterator
Iterator;
Iterator begin(Input_iterator it) const { return it->begin(); }
Iterator end (Input_iterator it) const { return it->end(); }
};
public:
typedef CGAL::Nested_iterator< Input_iterator, Nested_iterator_traits >
Recursive_flattening_iterator;
struct Flatten {
typedef Recursive_flattening_iterator result_type;
typedef Input_iterator argument_type;
Recursive_flattening_iterator
operator () (Input_iterator end, Input_iterator it) {
return Recursive_flattening_iterator(end,it);
}
};
};
/*! \ingroup LiS_Flattening_iterator
\brief Recursive application of \c Flattening_const_iterator
An instance \c Recursive_const_flattening<level,InputIterator>
of this class template contains a typedef \c Recursive_flattening_iterator.
This is a \c level -fold nested instance of
\c Flattening_const_iterator, where \c level can be any
non-negative integer. At each nesting level, begin and end
functors are supplied to \c Flattening_const_iterator
which assume that their arguments have a
\c const_iterator typedef and \c begin() and \c end()
member functions in the style of the STL.
The functor <tt>Flatten()(it)</tt> converts an \c InputIterator \c it
to a \c Recursive_flattening_iterator. Converting each endpoint
of an iterator range [first,beyond) yields an iterator range
in which \c level levels of packing into containers have been
unpacked. (In particular, the case \c level==0 is permissible
and a no-op.)
To get a \c const_iterator out of a container \c c of type \c C
which is not \c const itself, one can use syntax like
<tt>const_cast<const C&>(c).begin())</tt>. This may sometimes
be necessary in conjunction with \c Recursive_const_flattening.
*/
template< int level_, class InputIterator >
class Recursive_const_flattening {
public:
//! this instance itself
typedef Recursive_const_flattening Self;
//! this instance's first template argument
static const int level = level_;
//! this instance's second template argument
typedef InputIterator Input_iterator;
typedef Recursive_const_flattening<
level-1,
typename std::iterator_traits<Input_iterator>::value_type::const_iterator
> Nested_self;
private:
struct Nested_iterator_traits
{
typedef Input_iterator
Base_iterator;
typedef typename Nested_self::Recursive_flattening_iterator
Iterator;
Iterator begin(Input_iterator it) const { return typename Nested_self::Flatten()(it->end(),it->begin()); }
Iterator end (Input_iterator it) const { return typename Nested_self::Flatten()(it->end(),it->end()); }
};
public:
typedef CGAL::Nested_iterator< Input_iterator, Nested_iterator_traits >
Recursive_flattening_iterator;
//! conversion functor (model of STL concept \c AdaptableUnaryFunction )
struct Flatten {
//! result type
typedef Recursive_flattening_iterator result_type;
//! argument type
typedef Input_iterator argument_type;
//! conversion functor call
Recursive_flattening_iterator
operator () (Input_iterator end,Input_iterator it) {
return Recursive_flattening_iterator(end,it);
}
};
};
#ifdef DOXYGEN_RUNNING
/*! \ingroup LiS_Flattening_iterator
\brief (unimplemented)
This class template is unimplemented.
Only \c Recursive_const_flattening is available at this point.
*/
template <int level_, class InputIterator>
class Recursive_flattening { };
#endif // DOXYGEN_RUNNING
/*
* Part 2: Helper functions
*/
/*! \relates Recursive_const_flattening
* \brief map \c it to
* <tt>Recursive_const_flattening<level, InputIterator>::Flatten()(it)</tt>
*
* See \c Recursive_const_flattening for explanations.
* This function just exists to save typing via overloading resolution.
* You have to specify \c level explicitly in any case.
* For \c recursive_const_flattener<1,...>() , there is the
* shorthand \c const_flattener<...>() .
*/
template <int level, class InputIterator> inline
typename Recursive_const_flattening<level, InputIterator>
::Recursive_flattening_iterator
recursive_const_flattener(InputIterator end,InputIterator it) {
return typename Recursive_const_flattening<level, InputIterator>::Flatten()(end,it);
}
/*! \relates Flattening_const_iterator
* \brief map \c it to
* <tt>Recursive_const_flattening<1, InputIterator>::Flatten()(it)</tt>
*
* A function call <tt>fi = const_flattener(it)</tt> converts the iterator
* \c it to an instance of \c Flattening_const_iterator (see ibid.).
* The template arguments are chosen as follows:
* - \c InputIterator1 is \c InputIterator
* - \c InputIterator2 is \c InputIterator::value_type::const_iterator
* - \c UnaryFunction1/2 are set to functors that call \c begin()
* and \c end() member functions.
*
* This function helps to save typing and to avoid manual specification
* of \c UnaryFunction1/2.
*/
template <class InputIterator> inline
typename Recursive_const_flattening<1, InputIterator>
::Recursive_flattening_iterator
const_flattener(InputIterator end,InputIterator it) {
return typename Recursive_const_flattening<1, InputIterator>::Flatten()(end,it);
}
#ifdef DOXYGEN_RUNNING
/*! \relates Recursive_flattener
\brief (unimplemented)
This function template is unimplemented.
Only \c recursive_const_flattener is available at this point.
*/
template <int level, class InputIterator> inline
typename Recursive_flattening<level, InputIterator>
::Recursive_flattening_iterator
recursive_flattener(InputIterator it);
/*! \relates Flattening_iteratos
\brief (unimplemented)
This function template is unimplemented.
Only \c const_flattener is available at this point.
*/
template <class InputIterator> inline
typename Recursive_flattening<1, InputIterator>
::Recursive_flattening_iterator
flattener(InputIterator it);
#endif // DOXYGEN_RUNNING
} //namespace CGAL
#endif // LiS_FLATTENING_ITERATOR_H
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