Created
March 30, 2016 20:23
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Simple iterator zip implementation.
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/** | |
* Copyright 2016 Ruben De Smet | |
* | |
* 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; if not, write to the Free Software Foundation, | |
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. | |
*/ | |
#pragma once | |
#include <iterator> | |
#include <tuple> | |
#include <functional> | |
template<int ...> | |
struct seq { }; | |
template<int N, int ...S> | |
struct gens : gens<N-1, N-1, S...> { }; | |
template<int ...S> | |
struct gens<0, S...> { | |
typedef seq<S...> type; | |
}; | |
template <typename... IteratorType> | |
class zip_iterator | |
: public std::iterator<std::forward_iterator_tag, | |
std::tuple<decltype(std::bind(&IteratorType::operator*, nullptr)())...>> | |
{ | |
private: | |
std::tuple<IteratorType...> _iterators; | |
template<std::size_t I> | |
inline typename std::enable_if< I == sizeof...(IteratorType), void>::type advance() | |
{ | |
} | |
template<std::size_t I = 0> | |
inline typename std::enable_if< I < sizeof...(IteratorType), void>::type advance() | |
{ | |
++(std::get<I>(_iterators)); | |
advance<I+1>(); | |
} | |
template<int... S> | |
std::tuple<decltype(std::bind(&IteratorType::operator*, nullptr)())...> | |
deref_impl(seq<S...>) | |
{ | |
return std::make_tuple((*std::get<S>(_iterators))...); | |
} | |
template<std::size_t I> | |
inline typename std::enable_if< I == sizeof...(IteratorType), bool>::type | |
not_equals_impl(const zip_iterator& other) | |
{ | |
return true; | |
} | |
template<std::size_t I = 0> | |
inline typename std::enable_if< I < sizeof...(IteratorType), bool>::type | |
not_equals_impl(const zip_iterator& other) | |
{ | |
if(std::get<I>(_iterators) == std::get<I>(other._iterators)) | |
return false; | |
return not_equals_impl<I+1>(other); | |
} | |
public: | |
zip_iterator(const std::tuple<IteratorType...>& iterators) | |
: _iterators(iterators) | |
{ | |
} | |
std::tuple<decltype(std::bind(&IteratorType::operator*, nullptr)())...> | |
operator*() | |
{ | |
return deref_impl(typename gens<sizeof...(IteratorType)>::type()); | |
} | |
const zip_iterator& operator++() | |
{ | |
this->advance(); | |
return *this; | |
} | |
bool operator!=(const zip_iterator& other) | |
{ | |
return not_equals_impl(other); | |
} | |
}; | |
template<typename T> | |
class iterator_range | |
{ | |
T _beg; | |
T _end; | |
public: | |
iterator_range(T& beg, T& end) | |
: _beg(beg), _end(end) | |
{ | |
} | |
T begin() | |
{ | |
return _beg; | |
} | |
T end() | |
{ | |
return _end; | |
} | |
}; | |
template<typename IteratorType> | |
iterator_range<IteratorType> make_iterator_range(IteratorType begin, IteratorType end) | |
{ | |
return iterator_range<IteratorType>(begin, end); | |
} | |
template<typename... IterableType> | |
static auto zip(const IterableType&... containers) | |
-> iterator_range<zip_iterator<decltype(std::begin(containers))...>> | |
{ | |
zip_iterator<decltype(std::begin(containers))...> begin(std::make_tuple(std::begin(containers)...)); | |
zip_iterator<decltype(std::begin(containers))...> end(std::make_tuple(std::end(containers)...)); | |
return make_iterator_range(begin, end); | |
} |
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