compile time error in defining function with unknown return value

[mayank gupta]

I have added an external function written in C to CLIPS

its definition is

void findFromBSON(DATA_OBJECT_PTR returnValuePtr);

and added following to userfunctions.c 

66> extern void findFromBSON(DATA_OBJECT_PTR );

72> DefineFunction2( ...);

during compilation i am getting the following error

userfunctions.c: In function ‘UserFunctions’:

userfunctions.c:66: warning: parameter names (without types) in function declaration

Can you help me with what might have possibly gone wrong?

I have also added other functions, none of them which require returning unknown values using DATA_OBJECT_PTR, and those are working correctly.

[Lode Hoste]

I guess you lack the 'clipsEnv' parameter.
Try:

extern void findFromBSON(void *theEnv, DATA_OBJECT_PTR returnValuePtr);

Additional information might be helpful.

2012/4/21 mayank gupta <sharpsp...@gmail.com>:

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[mayank gupta]

Yes, I did try using

extern void findFromBSON(DATA_OBJECT_PTR returnValuePtr)

and it says error: expected ‘)’ before ‘returnValuePtr’

 
regarding Environment variable, should it be necessary for the function to be Environment specific? The other functions I have added do not require one.

Thanks

[Lode Hoste]

You forgot to #include "evaluatn.h" (which defines DATA_OBJECT_PTR).

With regard to the environment argument: yes, you need to define it
even though you won't use it.
CLIPS expects you to accept it. You should look into simple examples,
such as AbsFunction, IntegerFunction, etc.
I advice you to add it to your existing functions as well.

I have two related questions:
- How do you inspect the arguments functions without using the environment?
- And are you sure you don't know the return type of your
findFromBSON function? If it is an external pointer, you can define
(DefineFunction2) your function to return CLIPS type "a" which allows
you to easily return a void* to your data structure (without having to
manually set the DATA_OBJECT_PTR).

2012/4/22 mayank gupta <sharpsp...@gmail.com>:

[mayank gupta]

The error is during compilation of "userfunctions.c" . I will give it a try and tell you the results.

I had considered adding env argument but it wasn't on priority, and most of the examples in the Advanced programming guide do not use env argument. 

How do you inspect the arguments functions without using the environment? 

The functions mentioned in the Advanced programming guide are working. First use an RtnUnknown() call to get the argument in DATA_OBJECT then cast it to required type using DOTo...() functions.

And are you sure you don't know the return type of your findFromBSON function?

This actually is the result of a database query. So, I was trying to write a single function that would return int,string or other basic types from the result. I have added different functions to return int,strings etc but that's just too much of redundancy. A single function would reduce it. I guess I will give the other solution a try.

In the end, I'll try to write an application abstract for our use case.

Thanks