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

From: AJD (n.outpost_at_[hidden])
Date: 2007-12-08 15:24:14

"Eric Niebler" <eric_at_[hidden]> wrote in message 
news:475AEB69.9070304_at_boost-consulting.com...
>
> 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<float[3]>, vector2<float(&)[3]>, 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.

> 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.)

> Have you tried using proto::extends<>
> (or BOOST_PROTO_EXTENDS) to extend terminal<T>::type instead of
> terminal<float[3]>::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.