main.cc

/* vim: set et ft=cpp.doxygen sts=2 sw=2 ts=8 : */
/**
 * Copyright © 2014 Saleem Abdulrasool <compnerd@compnerd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 **/
 
#include "zip.hh"
 
#include <iostream>
#include <vector>
 
int main(int argc, char *argv[]) {
  char chars[] = { 'a', 'b', 'c' };
  std::vector<int> ints = { 1, 2, 3 };

  for (const auto & items : zip(chars, ints))
    std::cout << std::get<0>(items) << ", " << std::get<1>(items) << '\n';

  return EXIT_SUCCESS;
}

zip.hh

/* vim: set et ft=cpp.doxygen sts=2 sw=2 ts=8 : */
/**
 * Copyright © 2014 Saleem Abdulrasool <compnerd@compnerd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 **/

#ifndef zip_hh
#define zip_hh

#include <iterator>
#include <memory>
#include <numeric>
#include <tuple>
#include <type_traits>
#if __cplusplus >= 201400l
#include <utility>
#endif

// TODO(compnerd) make this interface more compatible with C++14
// make_integer_sequence
#if __cplusplus < 201400l
template <size_t ...>
struct sequence { };

template <size_t position_, size_t ... subsequence_>
struct generate : generate<position_ - 1u, position_ - 1u, subsequence_...> { };

template <size_t ... sequence_>
struct generate<0u, sequence_...> {
  typedef sequence<sequence_...> sequence;
};
#endif

namespace details {
template <typename>
struct iterable;

template <template <typename T_, typename Allocator_ = std::allocator<T_>>
          class container_, typename type_>
struct iterable<container_<type_>> {
  typedef container_<type_> type;
  typedef typename container_<type_>::const_iterator iterator;
  typedef typename std::remove_reference<type_>::type value_type;
};

template <typename type_, size_t bound_>
struct iterable<type_[bound_]> {
  typedef type_ type[bound_];
  typedef const type_ * iterator;
  typedef typename std::remove_reference<type_>::type value_type;
};

template <typename ... iterable_>
class zipped {
  const std::tuple<const typename iterable<iterable_>::type & ...> iterables_;

public:
  class const_iterator
    : public std::iterator<std::forward_iterator_tag,
                           const std::tuple<const typename iterable<iterable_>::value_type & ...>> {
    friend class zipped;

    std::tuple<typename iterable<iterable_>::iterator ...> iterators_;

    const_iterator(typename iterable<iterable_>::iterator ... iterators)
      : iterators_(iterators...) { }

    const_iterator(std::tuple<typename iterable<iterable_>::type & ...> &) = delete;
    const_iterator() = delete;

    template <size_t ... sequence_>
    const std::tuple<const typename iterable<iterable_>::value_type & ...>
    operator *(sequence<sequence_...>) const {
      return std::make_tuple(std::cref(*std::get<sequence_>(iterators_))...);
    }

    template <size_t ... sequence_>
    void advance(sequence<sequence_...>) {
      static_cast<void>(std::initializer_list<int>{
        [&]{ ++std::get<sequence_>(iterators_); return 0; }()...
      });
    }

    template <size_t ... sequence_>
    bool equals(const const_iterator & rhs, sequence<sequence_...>) const {
      auto il = std::initializer_list<int>{
        [&]{ return std::get<sequence_>(iterators_) == std::get<sequence_>(rhs.iterators_); }()...
      };
      return std::accumulate(std::begin(il), std::end(il), 0) == sizeof...(sequence_);
    }

  public:
    bool operator == (const const_iterator & rhs) const {
      return equals(rhs, typename generate<sizeof...(iterable_)>::sequence());
    }
    bool operator != (const const_iterator & rhs) const {
      return not operator == (rhs);
    }

    const_iterator & operator ++ () {
      advance(typename generate<sizeof...(iterable_)>::sequence());
      return *this;
    }
    const_iterator operator ++ (int) {
      const_iterator tmp = *this;
      operator ++ ();
      return tmp;
    }

    const std::tuple<const typename iterable<iterable_>::value_type & ...>
    operator * () const {
      return operator *(typename generate<sizeof...(iterable_)>::sequence());
    }
  };

private:
  template <size_t ... sequence_>
  const_iterator begin(sequence<sequence_...>) const {
    return const_iterator(std::begin(std::get<sequence_>(iterables_))...);
  }

  template <size_t ... sequence_>
  const_iterator end(sequence<sequence_...>) const {
    return const_iterator(std::end(std::get<sequence_>(iterables_))...);
  }

public:
  zipped(const typename iterable<iterable_>::type & ... iterables)
    : iterables_(iterables...) { }
  zipped(const typename iterable<iterable_>::type && ... iterables)
    : iterables_(iterables...) { }
  ~zipped() noexcept = default;

  zipped & operator = (const zipped &) = delete;

  const_iterator begin() const {
    return begin(typename generate<sizeof...(iterable_)>::sequence());
  }
  const_iterator end() const {
    // TODO(compnerd) truncate the iterators to the minimal width of the
    // iterables
    return end(typename generate<sizeof...(iterable_)>::sequence());
  }
};
}

template <typename ... iterable_>
details::zipped<iterable_...> zip(iterable_ && ... iterables) {
  return details::zipped<iterable_...>{ std::forward<iterable_>(iterables)... };
}

template <typename ... iterable_>
details::zipped<iterable_...> zip(iterable_ & ... iterables) {
  return details::zipped<iterable_...>{ iterables... };
}

#endif