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// Copyright (C) 2019 T. Zachary Laine
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//[ back_insert_iterator
#include <boost/stl_interfaces/iterator_interface.hpp>
#include <algorithm>
#include <vector>
#include <cassert>
// This is an output iterator that holds a reference to a container, and calls
// push_back() on that container when it is written to, just like
// std::back_insert_iterator. This is not a lot less code to write than the
// implementation of std::back_insert_iterator, but it demonstrates that
// iterator_interface is flexible enough to handle this odd kind of iterator.
template<typename Container>
struct back_insert_iterator : boost::stl_interfaces::iterator_interface<
#if !BOOST_STL_INTERFACES_USE_DEDUCED_THIS
back_insert_iterator<Container>,
#endif
std::output_iterator_tag,
typename Container::value_type,
back_insert_iterator<Container> &>
{
// For concept requirements.
back_insert_iterator() : c_(nullptr) {}
// Construct from a container.
explicit back_insert_iterator(Container & c) : c_(std::addressof(c)) {}
// When writing to *this, copy v into the container via push_back().
back_insert_iterator & operator=(typename Container::value_type const & v)
{
c_->push_back(v);
return *this;
}
// When writing to *this, move v into the container via push_back().
back_insert_iterator & operator=(typename Container::value_type && v)
{
c_->push_back(std::move(v));
return *this;
}
// Dereferencing *this just returns a reference to *this, so that the
// expression *it = value uses the operator=() overloads above.
back_insert_iterator & operator*() { return *this; }
// There is no underlying sequence over which we are iterating, so there's
// nowhere to go in next(). Do nothing.
back_insert_iterator & operator++() { return *this; }
using base_type = boost::stl_interfaces::iterator_interface<
#if !BOOST_STL_INTERFACES_USE_DEDUCED_THIS
back_insert_iterator<Container>,
#endif
std::output_iterator_tag,
typename Container::value_type,
back_insert_iterator<Container> &>;
using base_type::operator++;
private:
Container * c_;
};
// A convenience function that creates a back_insert_iterator<Container>.
template<typename Container>
back_insert_iterator<Container> back_inserter(Container & c)
{
return back_insert_iterator<Container>(c);
}
int main()
{
std::vector<int> ints = {{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}};
std::vector<int> ints_copy;
std::copy(ints.begin(), ints.end(), ::back_inserter(ints_copy));
assert(ints_copy == ints);
}
//]
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