From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!news.swapon.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: hreba <f_hreba@yahoo.com.br>
Newsgroups: comp.lang.ada
Subject: Interfaces.C questions
Date: Fri, 17 Mar 2017 22:12:25 +0100
Message-ID: <ej31ppF6c01U1@mid.individual.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Trace: individual.net tAegl25AJjCTTL6b87QdkgnbNw+AsE9uHjsvvfQEW2qaTu6khB
Cancel-Lock: sha1:h3VtqwxYbws2/L5hTqprJCatkOQ=
X-Mozilla-News-Host: news://News.Individual.DE:119
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Thunderbird/45.5.1
Xref: news.eternal-september.org comp.lang.ada:46413
Date: 2017-03-17T22:12:25+01:00
List-Id: <comp.lang.ada>

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