On 2 Feb 2006, at 01:51, Edward Diener wrote:
David Abrahams wrote:
Edward Diener <eddielee@tropicsoft.com> writes:
David Abrahams wrote:
Stefan Roiser <stefan.roiser@cern.ch> writes:
On 31 Jan 2006, at 19:40, David Abrahams wrote:
Stefan Roiser <stefan.roiser@cern.ch> writes:
> On 30 Jan 2006, at 17:08, Stefan Seefeld wrote: > > With interaction with objects I meant e.g. through the meta- > level > instantiate a class, get/set the data member values, call a > function > on that instance, retrieve the function's return value and so > on. I > may have missed that, but I couldn't find examples on the > synopsis > page for this functionality. > > Reflex code for this would look something like > > Type t = Type::ByName("foo"); > Object instance = t.Construct(); > Object ret_obj = instance.Invoke("myFunction"); Very interesting. Where do you get the object code for foo::myFunction? Or have you implemented a full C++ interpreter? foo::myFunction will be invoked through a stub function which is part of the dictionary library for class foo. A dictionary library may be dynamically loaded in a program. Soooo.... what about templates? Do you have to do something to manually instantiate them? Or do you do some kind of on-the-fly compilation? Since templates are not types, I would leave out the instantiation of templates into types, which is a compile-time mechanism, from a run-time reflection system
That presumes that the only thing worth reflecting about are types. I of course want reflection into templates (and not just class templates, either). But -- no offense intended of course --
No offense taken.
unless you're part of this effort, I'm not really asking what you would do. I want to know what the Cern people are doing and are planning to do.
The Cern people will have to speak for themselves.
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. With Reflex our scope was, as also pointed out by Edward, mainly the runtime reflection part. We are using Reflex at the moment for persistence of objects and interactive usage of objects (with language bindings - eg. Python). If I understood correctly your point, I think the two "xxxTemplate" classes are going in the direction of template introspection you intend to do, but you probably want to have more information. But how to retrieve this additional information? Related to this topic is the generation of dictionary information for a template instance. When generating dictionary information we normally select which information we want to generate (we don't want to generate the dictionary for vector<int> n times). So in general we generate it once and provide these "common" dictionary libraries to our users. In order to do that we have devloped a selection mechanism which is passed as an xml description to the dictionary generation step. To generate the dictionary for an vector of int and double would be generated like. MyVector.h ========== #include <vector> namespace { struct _Dict { std::vector<int> m1; std::vector<double> m2; }; } This syntax is currently needed because we use a quite old version of gccxml. In the future only the declaration of the template type will be needed to trigger gccxml to output the information for a template type. selection.xml ============= <lcgdict> <class pattern="std::vector<*>"/> </lcgdict> (yes, "<" and ">" are allowed in the xml descriptions as text for convenience) the syntax for the xml selections is more powerful than this simple example. You may have a look at http://seal-reflex.web.cern.ch/seal- reflex/gendict.html#selection_syntax for details. python genreflex.py MyVector.h -s selection.xml --gccxmplath=/my/path/ to/gccxml/bin The so into a library compiled dictionary from MyVector_rflx.cpp will when loaded into Reflex produce a TypeTemplate "std::vector" which contains a list of instances for the vector<int> and the vector<double> -- Stefan Roiser CERN, PH Department CH - 1211 Geneva 23 Mob:+41 76 487 5334 Tel:+41 22 767 4838 Fax:+41 22 767 9425