On Sun, Mar 28, 2010 at 10:44 AM, Steven Watanabe <watanabesj@gmail.com> wrote:
Okay. You might look at how https://svn.boost.org/trac/boost/ticket/861 solves the problem.
Indeed BOOST_MPL_HAS_TEMPLATE_XXX_TRAIT_DEF() does what I need but I still get the same "default parameter not yet parsed" error if I use this macro at *class* scope -- see below. The Boost.MPL doc indicates this macro should be used at namespace scope (and that works just fine). However, I need to use it to declare the metafunction at class scope -- is there a way to do that? For simplicity, here I am using BOOST_MPL_HAS_XXX_TRAIT_DEF() and I have remove the `Z` template parameter of `contract_f_`. If the macro was to work at class scope than I would use `BOOST_MPL_HAS_TEMPLATE_XXX_TRAIT_DEF()` from the Boost.MPL path indicated by Steven in order to support the `Z` template parameter. $ g++ -Wall -Werror test/noinherit/07.cpp test/noinherit/07.cpp: In instantiation of ‘const bool z::has_contract_f_<x, mpl_::bool_<false> >::value’: test/noinherit/07.cpp:17: instantiated from ‘z::has_contract_f_<x, mpl_::bool_<false> >’ test/noinherit/07.cpp:22: instantiated from here test/noinherit/07.cpp:17: error: the default argument for parameter 1 of ‘static char (& z::has_contract_f_<T, fallback_>::gcc_3_2_wknd::test(const volatile boost::mpl::aux::type_wrapper<U>*, boost::mpl::aux::type_wrapper<typename U::contract_f_>*))[2] [with U = x, T = x, fallback_ = mpl_::bool_<false>]’ has not yet been parsed // File test/noinherit/07.cpp #include <boost/mpl/has_xxx.hpp> #include <iostream> struct x { virtual void f() {} struct contract_f_ {}; }; struct y { void g() {} struct contract_g_ {}; }; struct z: x, y { BOOST_MPL_HAS_XXX_TRAIT_DEF(contract_f_) void f() {} struct contract_f_ {}; static const bool bx = has_contract_f_<x>::value; static const bool by = has_contract_f_<y>::value; }; int main() { std::cout << z::bx << std::endl; std::cout << z::by << std::endl; return 0; } Thanks, Lorenzo