Michael Marcin wrote:
Michael Marcin wrote:
Jody Hagins wrote:
Does that make any sense at all? Maybe.
IIUC what that forward declared partial specialization is doing is akin to saying: - I know the default implementation of tag_of can't be correct for boost::array<T,N> - There should be an implementation of tag_of that will make it work for boost::array<T,N> - I don't know what that implementation is, you or someone else better provide it
Is it then true that when proper definition of the partial specialization is provided this partial specialization of the declaration has no effect whatsoever?
If that is true and this is a compiler bug then perpahs we can use a configuration macro like BOOST_NO_DECLARTION_PARTIAL_SPECIALIZATION to simply omit these these forward declarations on compilers that choke on them (like CW 9.4 apparerently does).
Or maybe I still don't understand. Are these forward declaration partial specializations strictly necessary?
Yes. It's a means to prevent unwanted ODR violation. Fusion is modular. The support for boost::array comes when you include a header. Imagine a case where a TU does not include the header and another that does. Without the forward declaration, the second TU will pick up the default (non-specialized) implementation, which might or might not compile, but will certainly be a violation of ODR. Regards, -- Joel de Guzman http://www.boost-consulting.com http://spirit.sf.net