pygccxml-development

[pygccxml-development] pygccxml.declarations.templates.split, how to get the class declarations?

[Gustavo C. <gjc...@gm...>]

Hi, I have a problem here that I do not know where to begin to solve.  I use
pygccxml.declarations.templates.split(), but it returns a list of template
parameters as strings, while I need to declarations of the classes listed as
template arguments (long story, but I really do).  Is there a simple API in
pygccxml that would allow me to go from a string like
"ns3::dot11s::IeBeaconTimingUnit" to the actual declaration of the class?
Or any other method rather than templates.split() that would give me the
template args already as declarations?

Thanks in advance.

Regards,

-- 
Gustavo J. A. M. Carneiro
INESC Porto, Telecommunications and Multimedia Unit
"The universe is always one step beyond logic." -- Frank Herbert

Re: [pygccxml-development] pygccxml.declarations.templates.split, how to get the class declarations?

[Roman Y. <rom...@gm...>]

On Sun, Nov 15, 2009 at 6:22 PM, Gustavo Carneiro <gjc...@gm...> wrote:
> Hi, I have a problem here that I do not know where to begin to solve.  I use
> pygccxml.declarations.templates.split(), but it returns a list of template
> parameters as strings, while I need to declarations of the classes listed as
> template arguments (long story, but I really do).

Been there, done it :-)

>  Is there a simple API in
> pygccxml that would allow me to go from a string like
> "ns3::dot11s::IeBeaconTimingUnit" to the actual declaration of the class?
> Or any other method rather than templates.split() that would give me the
> template args already as declarations?

May be, lets see.

In general I found 2 different ways to solve this problem.

The first one is deterministic - if you have template instantiated
class in your hands and it has typedef for its template parameters,
then you can use this fact:

template< class T>
struct Wrapper{
    typedef T value_type;
...
};

pygccxml provides "internal_type_traits.get_by_name" method to get
reference to "type_t"

The second way: start parsing and searching :-).

I suggest you to take a look on container_traits.py module. It tries
to extract [value|element] type from std::[container]. It treats 2 use
cases:
* the input is class definition - so using typedef's defined in the
container class, it finds the actual template parameter type
* the input is class declaration ( in case in code was written forward
declaration ) - in this case the parsing of arguments is done and then
global namespace is searched. Take a look on
type_traits.impl_details.find_value_type method.

The second way works most of the time, when it doesn't you have few choices:
* create dummy type (dummy_type_t), which will return parameter string
as-is. In some of my cases, I use meta-programming to select the
desired functionality
* raise an exception and ask user to specify the type explicitly -
good error message will solve you headache and simplify a few things
for the user :-)

HTH

-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/

Re: [pygccxml-development] pygccxml.declarations.templates.split, how to get the class declarations?

[Gustavo C. <gjc...@gm...>]

2009/11/15 Roman Yakovenko <rom...@gm...>

> On Sun, Nov 15, 2009 at 6:22 PM, Gustavo Carneiro <gjc...@gm...>
> wrote:
> > Hi, I have a problem here that I do not know where to begin to solve.  I
> use
> > pygccxml.declarations.templates.split(), but it returns a list of
> template
> > parameters as strings, while I need to declarations of the classes listed
> as
> > template arguments (long story, but I really do).
>
> Been there, done it :-)
>
> >  Is there a simple API in
> > pygccxml that would allow me to go from a string like
> > "ns3::dot11s::IeBeaconTimingUnit" to the actual declaration of the class?
> > Or any other method rather than templates.split() that would give me the
> > template args already as declarations?
>
> May be, lets see.
>
> In general I found 2 different ways to solve this problem.
>
> The first one is deterministic - if you have template instantiated
> class in your hands and it has typedef for its template parameters,
> then you can use this fact:
>
> template< class T>
> struct Wrapper{
>    typedef T value_type;
> ...
> };
>
> pygccxml provides "internal_type_traits.get_by_name" method to get
> reference to "type_t"
>
> The second way: start parsing and searching :-).
>
> I suggest you to take a look on container_traits.py module. It tries
> to extract [value|element] type from std::[container]. It treats 2 use
> cases:
> * the input is class definition - so using typedef's defined in the
> container class, it finds the actual template parameter type
> * the input is class declaration ( in case in code was written forward
> declaration ) - in this case the parsing of arguments is done and then
> global namespace is searched. Take a look on
> type_traits.impl_details.find_value_type method.
>

It looks like type_traits.impl_details.find_value_type is what I need.  It
seems to work fine for my needs, i.e. template arguments are user classes.

I am only concerned about two things:

   - I'm not too fond of using "implementation details"

  - The function is relatively slow (almost half a second each query, and I
have a few dozen queries)

But other than that, I guess my problem is solved.

Thanks! :-)


> The second way works most of the time, when it doesn't you have few
> choices:
> * create dummy type (dummy_type_t), which will return parameter string
> as-is. In some of my cases, I use meta-programming to select the
> desired functionality
> * raise an exception and ask user to specify the type explicitly -
> good error message will solve you headache and simplify a few things
> for the user :-)
>
> HTH
>
> --
> Roman Yakovenko
> C++ Python language binding
> http://www.language-binding.net/
>



-- 
Gustavo J. A. M. Carneiro
INESC Porto, Telecommunications and Multimedia Unit
"The universe is always one step beyond logic." -- Frank Herbert

Re: [pygccxml-development] pygccxml.declarations.templates.split, how to get the class declarations?

[Roman Y. <rom...@gm...>]

On Tue, Nov 17, 2009 at 4:31 PM, Gustavo Carneiro <gjc...@gm...> wrote:
> It looks like type_traits.impl_details.find_value_type is what I need.  It
> seems to work fine for my needs, i.e. template arguments are user classes.
>
> I am only concerned about two things:
>
>    - I'm not too fond of using "implementation details"

:-). I don't have tests for this functionality. I checked that it
works for me ( extracting element, value types from sdt containers ).
If you submit a test for it, I will be glad to make this functionality
"public".

>   - The function is relatively slow (almost half a second each query, and I have a few dozen queries)

:-( Unfortunately I don't have a use case, which could stress this
function performance. Can you run the code under profile and send me
the data?

> But other than that, I guess my problem is solved.
>
> Thanks! :-)

You are welcome.

-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/