cpp-lazy-stream/include/stream/join.hpp

#pragma once

#include <iterator>

#include <iterator/join_iterator.hpp>
#include <stream/iterator.hpp>

namespace stream::detail {
template <typename C> class join_stream {
public:
  using iter_type = ::iterator::joining_iterator<iterator<C>>;

  using T = typename C::value_type;
  explicit join_stream(stream_base<C> const & sb) : source_(sb) {}

  iterator<T> begin() { return iter_type(source_); }
  iterator<T> end() { return iter_type(); }

private:
  stream_base<C> source_;
};

template <typename C>
stream_base<typename C::value_type> make_join(stream_base<C> const & sb) {
  return std::make_shared<join_stream<C>>(sb);
}

template <typename T>
template <typename F>
stream_base<traits::fmapped_t<T, F>> stream_base<T>::flatmap(F && func) && {
  return make_join(std::move(*this).map(func));
}

template <typename T>
template <typename F>
stream_base<traits::fmapped_t<T, F>>
stream_base<T>::flatmap(F && func) const & {
  return make_join(map(func));
}
}