Subject test fails in Iterator library: "F:\boost\boost/iterator/iterator_facade.hpp", line 534: error #265-D: function "boost::unit_test::input_iterator_facade<Derived, ValueType, Reference, Traversal>::equal [with Derived=boost::unit_test::basic_string_token_iterator<char, boost::unit_test::ut_detail::default_char_compare<char>>, ValueType=boost::unit_test::basic_cstring<const char>, Reference=boost::unit_test::basic_cstring<const char>, Traversal=boost::forward_traversal_tag]" is inaccessible return f1.equal(f2); class input_iterator_adaptor define like this: class input_iterator_facade : public iterator_facade<...> { ... private: friend class iterator_core_access; ... // iterator facade interface implementation bool equal( input_iterator_facade const& rhs ) const { ... } }; Any recommendations? Gennadiy.