Re: [boost] Reflection?

Subject: Re: [boost] Reflection?
From: Matus Chochlik (chochlik_at_[hidden])
Date: 2008-11-06 03:08:40

On Tue, Nov 4, 2008 at 9:47 PM, Jean-Louis Leroy <jl_at_[hidden]> wrote:
>
> I have renamed my library 'introspection' (to avoid clashing with Jeremy's
> work) and committed it to the sandbox.
>

FYI there already is a library named introspection in the vault
written by Joel Falcou.

> Today I wet my feet with Boost.Mirror. Using the doc (and the source code
> ;-)) I was able to make the code at the bottom of this message work. After a
> couple of hours 1/ I was very impressed 2/ I had a headache 3/ I was
> convinced that building runtime reflection on top of your work will be easy
> and 4/ I had found a bug ;-)

1/ I hope the impression was positive ;), thanks
2/ Sorry about the headache ;)
3/ I hope I will be helpful
4/ Thanks for spotting it !

>
>
> Sure, we must write the backend in such a way that it is useable stand-alone
> then write generators. My experience is that generators are fine as long as
> you have only one of them in a project but two won't coexist well, usually.
>

sounds reasonable.

> I'm running out of time, I have to work on serious things, namely preparing
> my trip to ... Slovakia !

Well, hope we can manage meet.

>
> Here's my Mirror hello-world, with the bug report:

Whee, this is the first program using mirror written by somebody
else than myself, that I've seen so far :)

>
> #include <iostream>
>
> #include <boost/mirror/meta_class.hpp>
> #include <boost/mirror/meta_inheritance.hpp>
> #include <boost/mirror/algorithm/for_each.hpp>
>
> using namespace std;
> using namespace boost;
> using namespace boost::mirror;
>
> struct animal {
>  int age;
> };
>
> struct mammal : virtual animal {
> };
>
> struct carnivore : virtual animal {
> };
>
> struct dog : mammal, carnivore {
> };
>
> namespace boost { namespace mirror {
>
> BOOST_MIRROR_REG_TYPE_GLOBAL_SCOPE(animal)
> BOOST_MIRROR_REG_CLASS_ATTRIBS_BEGIN(animal)
> BOOST_MIRROR_REG_SIMPLE_CLASS_ATTRIB(_, int, age)
> BOOST_MIRROR_REG_CLASS_ATTRIBS_END
>
> BOOST_MIRROR_REG_TYPE_GLOBAL_SCOPE(mammal)
> BOOST_MIRROR_REG_BASE_CLASSES_BEGIN(mammal)
> BOOST_MIRROR_REG_VIRTUAL_BASE_CLASS(0, public, animal)
> BOOST_MIRROR_REG_BASE_CLASSES_END
>
> // watch out: BOOST_MIRROR_REG_SINGLE_BASE_CLASS_VIRTUAL(mammal, public,
> animal)
> // doesn't work because it calls BOOST_MIRROR_REG_BASE_CLASS_VIRTUAL
> // instead of BOOST_MIRROR_REG_VIRTUAL_BASE_CLASS

Again, thanks for your bug report, I'm going to fix it ASAP.

>
> BOOST_MIRROR_REG_TYPE_GLOBAL_SCOPE(carnivore)
> BOOST_MIRROR_REG_BASE_CLASSES_BEGIN(carnivore)
> BOOST_MIRROR_REG_VIRTUAL_BASE_CLASS(0, public, animal)
> BOOST_MIRROR_REG_BASE_CLASSES_END
>
> BOOST_MIRROR_REG_TYPE_GLOBAL_SCOPE(dog)
> BOOST_MIRROR_REG_BASE_CLASSES_BEGIN(dog)
> BOOST_MIRROR_REG_BASE_CLASS(0, public, mammal)
> BOOST_MIRROR_REG_BASE_CLASS(1, public, carnivore)
> BOOST_MIRROR_REG_BASE_CLASSES_END
>
> } }
>
> struct print_attribute {
>  template<typename ATTRIBUTE> void operator()(ATTRIBUTE) {
>   cout << ATTRIBUTE::get_name(mpl::false_(), std::char_traits<char>()) <<
> endl;
>  }
> };
>
> struct print_base {
>  template<typename CLASS> void display(CLASS, virtual_base_) {
>   cout << "virtual " << CLASS::meta_base_class::get_name(mpl::false_(),
> std::char_traits<char>()) << endl;
>  }
>  template<typename CLASS> void display(CLASS, nonvirtual_base_) {
>   cout << CLASS::meta_base_class::get_name(mpl::false_(),
> std::char_traits<char>()) << endl;
>  }
>  template<typename CLASS> void operator()(CLASS c) {
>   display(c, CLASS::inheritance_specifier());
>  }
> };
>
> int main() {
>  mirror::for_each< meta_class<animal>::attributes >(print_attribute());
>  mirror::for_each< meta_class<mammal>::base_classes >(print_base());
>  mirror::for_each< meta_class<dog>::base_classes >(print_base());
>  return 0;
> }
>
>
> Cordially,
> Jean-Louis
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Best,

--matus