Interfaces.C questions

[hreba <f_hreba@yahoo.com.br>]

These are my first steps with Interfaces.C:

----------------------------------------------------------------------
with Interfaces.C;

package GSL is

    package C renames Interfaces.C;

    type size_t is new C.int;
    type Real_Function is access function (x: C.double) return C.double;

    function Bessel_J0 (x: C.double) return C.double;

    function Integration_QNG
      (f: Real_Function;
       a, b, epsabs, epsrel: C.double;
       result, abserr: out C.double;
       neval: out size_t)
      return C.int;

private

    pragma Import (C, Bessel_J0,		"gsl_sf_bessel_J0");
    pragma Import (C, Integration_QNG,	"gsl_integration_qng");

end GSL;
------------------------------------------------------------------------

No problem with function Bessel_J0. But Integration_QNG gets me:

gsl.ads:19:07: functions can only have "in" parameters.

The C prototype of this function is:

int gsl_integration_qng (const gsl function * f , double a , double b ,
double epsabs , double epsrel , double * result , double * abserr , size 
t * neval )

So my questions are:

1. How do I translate C functions which return non-void and which 
additionally use pointers for out parameters? Do I have to use pointers 
in my Ada program?

2. On my platform size_t is C.int. How can I define size_t in a 
platform-independent way?

3. The C function above needs a pointer to a function as parameter. Is 
my translation to Ada correct?

-- 
Frank Hrebabetzky		+49 / 6355 / 989 5070