Re: [Boost-users] SFINAE broken in Visual C++ Express?

on Tue Oct 30 2007, "Ovanes Markarian" wrote:

Hello!

Does anybody else experience a problem using enable_if templates in Visual C++ Express 2005 SP1? I get compiler errors in this code:

template<class LookUpType_> typename boost::enable_if_c::type at(LookUpType_ const& key)const { return has_key(view_, key); }

template<class LookUpType_> typename boost::disable_if_c::type at(LookUpType_ const& key) { return has_key(view_, key); }

It blames that type is not a member of enable_if_c or disable_if_c? This is really strance, since this should not be considered by compiler as a possible template instantiation. is_const is an enum value containing either true or false.

In order for SFINAE to work, at least one argument to [dis|en]able_if has to depend on a template argument (in this case, LookUpType_ is the only one). As written, none of them do. I don't know what you're doing with is_const, but at least in the Boost world that is a template that requires a template argument in that context. For example, template<class LookUpType_> typename boost::disable_if_c, result_type>::type at(LookUpType_ const& key) { return has_key(view_, key); } HTH, -- Dave Abrahams Boost Consulting http://www.boost-consulting.com