component changed; owner set

viboes — Sat, 06 Jun 2009 15:01:35 GMT

owner set to Dave Abrahams
component None → iterator

paul — Wed, 30 Dec 2009 14:53:33 GMT

Any update on this? I would like to add that this is not simply a effeciency issue, it leads to erroneous behavior if a boost iterator is used with std::advance and if nothing else there should be a strong warning in the documentation, i.e. the following test fails std::advance(some_boost_iterator.end(), -1) != some_boost_iterator.end().

Simple test,

int main()
{
        test_iter itr(0);
        itr++;
        assert(*itr == 1);
        ++itr;
        assert(*itr == 2);
        itr+=8;
        assert(*itr == 10);
        itr-=8;
        assert(*itr == 2);
        --itr;
        assert(*itr == 1);
        itr--;
        assert(*itr == 0);
        std::advance(itr, 5); // passes, but less efficient than expected
        assert(*itr == 5);
        std::advance(itr, -5); // iterator is not moved
        assert(*itr == 0); // FAILURE, *itr == 5
}
struct test_iter
  : public boost::iterator_facade<
        test_iter
      , int
      , boost::random_access_traversal_tag,
          int
    >
{
 public:
    test_iter() : m_value(0) {}
    explicit test_iter(int v) : m_value(v) {}
    test_iter(test_iter const& other) : m_value(other.m_value) {}
    bool equal(test_iter const& other) const
    {
        return this->m_value == other.m_value;
    }
    void increment() { ++m_value; }
    void decrement() { --m_value; }
    int dereference() const {
                return m_value;
        }
        void advance(difference_type offset)
        {
                m_value+=offset;
        }
        difference_type distance_to(const test_iter& rhs)
        {
                return m_value-rhs.m_value;
        }
        int m_value;
};

owner changed

Dave Abrahams — Wed, 21 Nov 2012 19:42:25 GMT

owner changed from Dave Abrahams to jeffrey.hellrung

anonymous — Mon, 22 Feb 2016 02:25:30 GMT

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Boost C++ Libraries: Ticket #2539: advance() and distance() for new iterator concepts

component changed; owner set

owner changed