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#ifndef PYTHONIC_INCLUDE_ITERTOOLS_PERMUTATIONS_HPP
#define PYTHONIC_INCLUDE_ITERTOOLS_PERMUTATIONS_HPP
#include "pythonic/include/utils/functor.hpp"
#include "pythonic/include/types/dynamic_tuple.hpp"
#include <iterator>
#include <vector>
PYTHONIC_NS_BEGIN
namespace itertools
{
/** Permutation iterator
*
* It wraps a vector && provide an iteration over every possible
* permutation of the vector. The permutations are represented as
*dynamic_tuple
* of elements.
*
* The following iterator:
*
* permutations_iterator([0, 1, 2])
*
* yields the following suite:
*
* [(0, 1, 2), (0, 2, 1), (1, 0, 2), (1, 2, 0), (2, 0, 1), (2, 1, 0)]
*
*/
template <class T>
struct permutations_iterator
: std::iterator<std::forward_iterator_tag,
types::dynamic_tuple<typename T::value_type>, ptrdiff_t,
types::dynamic_tuple<typename T::value_type> *,
types::dynamic_tuple<typename T::value_type> /* no ref*/
> {
// Vector of inputs, contains elements to permute
std::vector<typename T::value_type> pool;
// The current permutation as a dynamic_tuple of index in the pool
// Internally it always has the same size as the pool, even if the
// external view is limited
std::vector<long> curr_permut;
// Size of the "visible" permutation
size_t _size;
bool end; // sentinel marker
permutations_iterator();
permutations_iterator(std::vector<typename T::value_type> const &iter,
size_t num_elts, bool end);
/** Build the permutation visible from the "outside" */
types::dynamic_tuple<typename T::value_type> operator*() const;
/* Generate next permutation
*
* If the size of the permutation is smaller than the size of the
* pool, we may have to iterate multiple times
*/
permutations_iterator &operator++();
bool operator!=(permutations_iterator const &other) const;
bool operator==(permutations_iterator const &other) const;
bool operator<(permutations_iterator const &other) const;
};
template <class T>
// FIXME document why this inheritance???
struct _permutations : permutations_iterator<T> {
using iterator = permutations_iterator<T>;
using value_type = typename iterator::value_type;
_permutations();
_permutations(T iter, long elts);
iterator const &begin() const;
iterator begin();
iterator end() const;
};
template <typename T0>
_permutations<T0> permutations(T0 iter, long num_elts);
template <typename T0>
_permutations<T0> permutations(T0 iter);
DEFINE_FUNCTOR(pythonic::itertools, permutations);
}
PYTHONIC_NS_END
/* type inference stuff {*/
#include "pythonic/include/types/combined.hpp"
template <class E, class T>
struct __combined<E, pythonic::itertools::_permutations<T>> {
using type = typename __combined<
E, container<
typename pythonic::itertools::_permutations<T>::value_type>>::type;
};
/* } */
#endif
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