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From: Jacob Sparre Andersen <sparre@nbi.dk>
Newsgroups: comp.lang.ada
Subject: Problematic type definition in Interfaces.Fortran
Date: Mon, 26 Nov 2001 16:15:14 +0100
Organization: Centre for Chaos and Turbulence Studies, Niels Bohr Institute
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Date: 2001-11-26T16:15:14+01:00
List-Id: <comp.lang.ada>

I have noticed what I consider a rather problematic type
definition in package Interfaces.Fortran. RM B.5(9):

type Complex is new Single_Precision_Complex_Types.Complex;

Since package
Ada.Numerics.Generic_Complex_Elementary_Functions is
instantiated using an instantiation of package
Ada.Numerics.Generic_Complex_Types, it is not possible to
instantiate it for type Interfaces.Fortran.Complex.

And authors of Fortran bindings (such as "lapada") have a
habit of using type Interfaces.Fortran.Complex. :-(

Here is a code example that illustrates the problem:

----------
with Ada.Numerics.Generic_Complex_Elementary_Functions;
with Interfaces.Fortran; use Interfaces.Fortran;

procedure Hack_Virker is
   package KomplekseFunktioner is
     new Ada.Numerics.Generic_Complex_Elementary_Functions
       (Interfaces.Fortran.Single_Precision_Complex_Types);
   use KomplekseFunktioner;

   Psi :
Interfaces.Fortran.Single_Precision_Complex_Types.Complex;
   II  : constant
Interfaces.Fortran.Single_Precision_Complex_Types.Complex
           := (0.0, 1.0);
begin -- Hack_Virker
   Psi := Exp(II);
end Hack_Virker;
----------

The problem is that since "Interfaces.Fortran.Complex" is
derived from
"Interfaces.Fortran.Single_Precision_Complex_Types.Complex",
and not just a subtype of
"Interfaces.Fortran.Single_Precision_Complex_Types.Complex",
there is no package to use for instantiating package
Ada.Numerics.Generic_Complex_Elementary_Functions.

Is there a very good reason for not making
"Interfaces.Fortran.Complex" a subtype of
"Interfaces.Fortran.Single_Precision_Complex_Types.Complex"?

Jacob
-- 
Sk�ne Sj�lland Linux User Group - http://www.sslug.dk/
N�ste m�de: IT-lovgivning.
Tirsdag den 27. november 2001 i Symbion, Fruebjergvej 3.