Re: [boost] Re: [C++-sig] Using Boost Pyhton as a C++ Reflection Library

From: Lin Xu (risingdragon3_at_[hidden])
Date: 2003-05-10 03:32:28

>     template <class T, T v, char const*> struct member {};
>     template <class T> struct members;
>
>     template <>
>     struct members<X>
>       : mpl::vector<
>             member<int(X::*)(double), &X::f, "f">
>           , member<char*(X::*), &X::x, "x">
>           , member<int&, X::y, "y">
>         >
>     {
>     };
I realize that you were quickly drafting this code, but wouldn't you need to 
define the names as const char*, and that the member tempalte should take a 
member pointer?

The problem is that string constants have to be defined *outside* the 
definition of the template, as I remember from discussion from a compile 
time string class. But you can't really do much compile time manipulation of 
strings, anyway. For starters, comparision (is_same) of template classes 
with string constants (predictably) fail when you define two different const 
char*'s that contain the same thing.
I think that the string name should be relegated to the runtime aspect of 
reflection - unless, the only thing being supported is runtime reflection 
(perhaps in conjunction with dynamic_any).
At compile time, the only way to give a member a unique identity is with 
some sort of tag class, which later on can be used to get the value:

struct prop_x {};
...
struct y { int x };
//define the reflection
y test;
reflect<y>::get<prop_x>(test) = 10.4;

At runtime, of course, things are different. Something like this may be 
possible:
template <> struct reflect<y> : public reflect_base<y> {
   MEMBER(x);
};

reflect<y>::bind_to(test)["x"] = 10;

Comments?

_________________________________________________________________
MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*.  
http://join.msn.com/?page=features/virus