Re: [eclipse-clp-users] ec_external definition not included if EC_EMBED is defined.

Hi Kish,

I am extending PyCLP by adding the capability to implementing predicates 
in Python.
PyCLP interfaces to Eclipse by using the provided c interface.
So for me it is easier to register a new predicate from c instead of 
posting external/2 and then execute resume.
However, in case you will find that the error is in the documentation I 
can always fall-back to the second solution.


Beside this issue I have another issue.
In Python, functions are defined at execution time (function are 
converted in bytecode at runtime) and python functions are not mapped to 
c functions that I can register to Eclipse.
So I have a c proxy function registered as call_python/2. First argument 
shall be atom matching the name of python function and the second 
argument is a list that I pass to the python function .
This is not a ideal implementation.
My preferred solution would be:
register all  predicates (to be linked to python functions) to the same 
c function. In this c function I get the functor of invoking predicate 
e.g. ec_functor() then I can search in a python hash table the right 
python function and call it using c to python interface functions.

I don't expect that my use case justifies an effort in this direction by 
if you have the opportunity.... :-).
Best Regards
Oreste Bernardi

PS.
When it is possible, let me know where is the bug so I can update my 
library.

On 30/11/2012 18:51, Kish Shen wrote:
> Hi Oreste,
>
> As I think Joachim may still be on holiday, I will try and give you 
> some answer to your question...
>
> Yes, it does look like if you include eclipse.h, this defines 
> EC_EMBED, and so ec_external() would not be available for use.
>
> It is not clear to me that the error is therefore ec_external() should 
> be moved out of the EC_EMBED ifdef, because I am not sure if 
> ec_external() was deliberately excluded (or removed, after the manual 
> was written) from the C/C++ interface, and the error (in this case) 
> would be mentioning it in the embedding and interface manual.
>
> The usual way of linking predicates defined in C/C++ is to do it in 
> the ECLiPSe code via external/2, after the creation of the module for 
> the ECLiPSe code, but before the use of the external predicate. Using 
> ec_external() is given as an alternative to doing this in C rather 
> than ECLiPSe, but it is not clear to me how useful this is, because 
> the intended usage of the C interface is for ECLiPSe code to be in its 
> own file, rather than as part of the C program file, so using 
> external/2 seems the most natural way to include external predicates.
>
> Do you have a use case for using ec_external(), where you think it 
> would be useful?
>
> Cheers,
>
> Kish
>
> On 27/11/2012 18:40, Oreste wrote:
>> Hi,
>> I am working on external predicates implemented in C.
>> I have just seen that int ec_external(dident pred, int(*fct)(), dident
>> module) definition is not included if EC_EMBED is defined.
>> See embed.h.
>>
>> I guess this is a bug because in the documentation this function is
>> declared as part of embedded interface.
>> Is this correct ?
>>
>> Best Regards
>> Oreste Bernardi
>>
>>
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