[C++-sig] Exposing a generic template system in Boost.Python

[Francesco Biscani]

Hello Stefan and Nikolay,

thanks for the replies. I have been using as well approaches similar to
those you outlined. My main concern is the automation of the whole
procedure. I have a fairly complicated hierarchy of template classes that I
am exposing, and I need to be able to add new exposed instances in a kind
of programmatic way (e.g., I am using a global counter n that gets
increased each time a new instance is exposed, and I am calling the exposed
classes "__vecor_type_0", "__vecor_type_1", ..., "__vecor_type_n"). Then I
need to re-establish the connection between these names and the "template
system" implemented on the Python side.

I think it would be nice to have a Boost.Python mechanism to handle this
type of usage, but for now I will try to get something working for my
specific case (and then maybe reply here if I manage and if there is
interest). Thanks for the help and kind regards,

  Francesco.


On 19 March 2014 20:27, Nikolay Mladenov <nikolay.mladenov at gmail.com> wrote:

> To add to Stefan's answer:
>
> I do the the same and also use visitors to add the same sets of members to
> classes, with possible customizations via trait classes.
>
> HTH
>
>
> On Wed, Mar 19, 2014 at 1:36 PM, Stefan Seefeld <stefan at seefeld.name>wrote:
>
>> Francesco,
>>
>> I have done something like what you are suggesting. It essentially boils
>> down to defining a function template like
>>
>> template <typename T>
>> void define_vector(char const *name)
>> {
>>    class_<...> vector(name);
>>   ...
>> }
>>
>>
>> and then calling that multiple times:
>>
>>   define_vector<int>("IVector");
>>   define_vector<long>("LVector");
>>   ...
>>
>> Providing a factory function that instantiates one of those based on a
>> value-type selector as you want can be easily done on the Python side.
>>
>> I don't think this can be automated any further. In particular, it is
>> clear that any type you may want to instantiate in Python has to be
>> compiled explicitly into the extension module. I.e., you need to
>> explicitly instantiate the templates above, by explicitly calling the
>> functions for the types you want to see supported at runtime. There is
>> no JIT compilation for this.
>>
>>     Stefan
>>
>> --
>>
>>       ...ich hab' noch einen Koffer in Berlin...
>>
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>
>
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