Re: [Boost-users] boost.proto optimization on MSVC (2005/2008)

AJD wrote:

"Eric Niebler" wrote in message news:475AEB69.9070304@boost-consulting.com...

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I'm confused. So your vector2<> type is intended as a wrapper for any kind of terminal, not arrays?

vector2<> doesn't wrap terminals, it just wraps regular types to provide uniform access to them with a vector (math vector) interface. This way vector2, vector2, and vector2<D3DXVECTOR> could all be used with expressions regardless of their underlying type, and additional types can be used just by specializing vector2<T> and providing the subscript operator as well as some traits.

OK...

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So how is your example different than any of the examples in proto's docs?

I based it off of the lazyvector example, but the code does not optimize as expected. (In fact, all I really did was swap out the vector type.)

Your code doesn't optimize because you replaced the terminal type with something that proto doesn't recognize as a terminal.

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Have you tried using proto::extends<> (or BOOST_PROTO_EXTENDS) to extend terminal<T>::type instead of terminal::type ? You'll also need to patch up your grammar to accept any kind of terminal.

I'm not sure that's the correct approach... proto should not have to know about the internal type of vector2<> at all. I could do this with a helper type where vector2 extends vector2_internal which contains all the functionality, but then I'm faced with the problem that the many specializations of vector2_internal<> could have different constructors which would no longer be accessible through the vector2 interface.

Proto builds trees. Trees have terminals and non-terminals. Any type which proto doesn't recognize is assumed to be a terminal and is automatically wrapped. Types which proto recognizes are: - proto::expr<> - Anything that inherits from proto::extends<> - Anything type that uses the BOOST_PROTO_EXTENDS macro Your vector terminals must conform to one of those. Otherwise, proto will make it conform by wrapping it, and that makes your optimizer's job harder. The code I sent has a specialization for vector2. Can't you just add additional specializations to handle the terminals you're interested in? Or define vector2 once as: template< typename T, typename U = proto::is_proto_expr > struct vector2 { BOOST_PROTO_EXTENDS( typename proto::terminal<T>::type , vector2<T> , VectorDomain ) typedef typename vector_traits<T>::value_type value_type; value_type & operator [](std::size_t i) { return vector_traits<T>::index(proto::arg(*this), i); } value_type const & operator [](std::size_t i) const { return vector_traits<T>::index(proto::arg(*this), i); } }; And then specialize vector_traits<>. -- Eric Niebler Boost Consulting www.boost-consulting.com