Previously, I had implemented a nice complex_to_real iterator adapter. It used the older real(z) and imag(z) that return value, not ref. Now it seems it gcc-4.0.1, at least, there are .imag() and .real() that return ref. So I thought I'd update c_to_r adaptor to use them. But, I can't seem to get this to work. Any hints? Here's what I get: g++ -c -I src test2.cc /usr/include/boost/iterator/iterator_facade.hpp: In static member function ‘static typename Facade::reference boost::iterator_core_access::dereference(const Facade&) [with Facade = boost::c_to_r_adapt<__gnu_cxx::__normal_iterator<main()::Complex*, std::vector<main()::Complex, std::allocator<main()::Complex> > > >]’: /usr/include/boost/iterator/iterator_facade.hpp:635: instantiated from ‘Reference boost::iterator_facade<I, V, TC, R, D>::operator*() const [with Derived = boost::c_to_r_adapt<__gnu_cxx::__normal_iterator<main()::Complex*, std::vector<main()::Complex, std::allocator<main()::Complex> > > >, Value = double, CategoryOrTraversal = boost::random_access_traversal_tag, Reference = double&, Difference = ptrdiff_t]’ /usr/lib/gcc/x86_64-redhat-linux/4.0.1/../../../../include/c++/4.0.1/bits/stl_algobase.h:285: instantiated from ‘static _OI std::__copy<_BoolType, std::random_access_iterator_tag>::copy(_II, _II, _OI) [with _II = double*, _OI = boost::c_to_r_adapt<__gnu_cxx::__normal_iterator<main()::Complex*, std::vector<main()::Complex, std::allocator<main()::Complex> > > >, bool _BoolType = false]’ /usr/lib/gcc/x86_64-redhat-linux/4.0.1/../../../../include/c++/4.0.1/bits/stl_algobase.h:317: instantiated from ‘_OI std::__copy_aux(_II, _II, _OI) [with _II = double*, _OI = boost::c_to_r_adapt<__gnu_cxx::__normal_iterator<main()::Complex*, std::vector<main()::Complex, std::allocator<main()::Complex> > > >]’ /usr/lib/gcc/x86_64-redhat-linux/4.0.1/../../../../include/c++/4.0.1/bits/stl_algobase.h:335: instantiated from ‘static _OI std::__copy_normal<true, false>::copy_n(_II, _II, _OI) [with _II = __gnu_cxx::__normal_iterator<double*, std::vector<double, std::allocator<double> > >, _OI = boost::c_to_r_adapt<__gnu_cxx::__normal_iterator<main()::Complex*, std::vector<main()::Complex, std::allocator<main()::Complex> > > >]’ /usr/lib/gcc/x86_64-redhat-linux/4.0.1/../../../../include/c++/4.0.1/bits/stl_algobase.h:387: instantiated from ‘_OutputIterator std::copy(_InputIterator, _InputIterator, _OutputIterator) [with _InputIterator = __gnu_cxx::__normal_iterator<double*, std::vector<double, std::allocator<double> > >, _OutputIterator = boost::c_to_r_adapt<__gnu_cxx::__normal_iterator<main()::Complex*, std::vector<main()::Complex, std::allocator<main()::Complex> > > >]’ test2.cc:12: instantiated from here /usr/include/boost/iterator/iterator_facade.hpp:517: error: invalid initialization of reference of type ‘double&’ from expression of type ‘const double’