[Boost-users] Re: units library

I'm guessing that template parameters are a no-go. OTOH can I register

"Andy Little" wrote the

following:

template < typename A, template <typename> class Op, typename B, typename Enable = void > struct binary_operation;

(Basically I am not able to compile and wonder if this may be the issue) .

Yes, unfortunately we only support type and integral template parameters, but not template template parameters :-( Supporting template template parameters just looks impossible to me, since templates can't be returned from metafunctions (you can't typedef them). OTOH, if you are willing to change your interface just a little, and just use a wrapper over your operation, something like this: struct plus_identity { template struct apply : plus{}: }; (pass plus_identity, and use Op::template apply instead of Op) then your template would accept a simple type parameter rather than a template template parameter, and would be fully compatible with the BOOST_TYPEOF system. The drawback -- the code need to be changed to cooperate with the BOOST_TYPEOF system; The benefit -- you have a portable typeof right now, long time before it is in the standard, and even longer time before it's implemented by most major vendors. Also we use native typeof when possible, so on those compilers that do implement it there is no compile-time performance penalty. Regards, Arkadiy