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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Interfaces.C questions
Date: Sat, 18 Mar 2017 17:27:19 +0100
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Date: 2017-03-18T17:27:19+01:00
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On 03/18/2017 04:46 PM, hreba wrote:
>
> struct gsl_function_struct
> {
>   double (* function) (double x, void * params);
>   void * params;
> };
> typedef struct gsl_function_struct gsl_function ;
>
> Can anybody please tell me how to translate this into Ada? I have no idea how to
> handle the void pointers.

Presuming that this is C's equivalent of a private type, and all allocation will 
be handled by the library, then the equivalent of void* is any convention-C 
access type. I'd probably write

type Void_Ptr is access all Integer;
pragma Convention (C, Void_Ptr);

type GSL_Function_Ptr is access
    function (X : Interfaces.C.Double; Params : Void_Ptr)
return Interfaces.C.Double;
pragma Convention (C, GSL_Function_Ptr);

type GSL_Function is record
    Func   : GSL_Function_Ptr;
    Params : Void_Ptr;
end record;
pragma Convention (C, GSL_Function);

-- 
Jeff Carter
"Pray that there's intelligent life somewhere up in
space, 'cause there's bugger all down here on earth."
Monty Python's Meaning of Life
61