I'm trying to use the function traits to extract the return type of a template parameter, but it's not compiling. Any ideas what's wrong here? -------- begin simplified code ------ template<typename Proc> class CacheValue { typedef boost::function_traits<Proc>::R ReturnType; template<typename Arg1> ReturnType operator () ( Arg1 arg1 ) { /* do something */ } }; CacheValue aValue; -------- end simplified code ------ Gets the error: Error : illegal use of incomplete struct/union/class 'boost::detail::function_traits_helper' (point of instantiation: 'main()') (instantiating: 'CacheValue') (instantiating: 'boost::function_traits') function_traits.hpp line 170 public detail::function_traits_helper Error : 'R' is not a member of class 'boost::function_traits' (point of instantiation: 'main()') (instantiating: 'CacheValue') HelloWorld.cp line 57 CacheValue<TickGetter> ticks ( GetCount ); Environment: MacOS 10.2.2, CodeWarrior 8.3, boost from CVS this morning. It seems as if the "add_pointer" in function_traits_helper is messing things up. Of course, it's more likely that I am using this wrong ;-) Thanks in advance! -- -- Marshall Marshall Clow Idio Software mailto:marshall@idio.com Hey! Who messed with my anti-paranoia shot?