Re: [boost] Library Proposal: Reflection for C++

From: Edward Diener (eddielee_at_[hidden])
Date: 2006-02-03 17:30:20

Stefan Roiser wrote:

> 
> Reflex does provide reflection information for template instances  
> (classes, functions) and template families. An instantiated template  
> class is a Reflex::Type, an instantiated template function is a  
> Reflex::Member. There are two additional classes in the API  
> (TypeTemplate, MemberTemplate) which will allow the user to  
> introspect/interact with a template family (e.g. std::vector<T>), but  
> this information only get's filled once the first template instance  
> in the dictionary source code comes along.
> 
> The TypeTemplate/MemberTemplate currently allow to loop over template  
> parameters, look at parameter defaults (if any, this also needs some  
> extra handling - gxxml won't give us this info) and loop over the  
> instances of this template currently available in the system.

I think it is a commendable goal in Reflex to be able to reflect the 
parameter types for any given template instantiation, since this 
information may be valuable and usable at run-time. After all, at 
run-time, information about a template type should be just as accesible 
regarding finding type information than any other type. One of the 
pieces of information about a template type is the parameter types which 
are used to instantiate the template, so run-time reflection should 
include such information. But I feel that information about the template 
declaration/definition itself belongs in the realm of a compile-time 
reflection system, not a run-time reflection system, and can serve no 
purpose in a run-time reflection system.