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Date: Sat, 18 Mar 2017 16:24:00 -0700 (PDT)
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Subject: Re: Interfaces.C questions
From: Leo Brewin <leo.brewin@internode.on.net>
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Xref: news.eternal-september.org comp.lang.ada:46420
Date: 2017-03-18T16:24:00-07:00
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Hi Frank,

I'd be really interested to see a minimal working example once you've got it running.
I'd like to be able to use GSL in my own codes.

Cheers,
Leo

On Saturday, March 18, 2017 at 8:12:28 AM UTC+11, hreba wrote:
> 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