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From: "David C. Hoos" <david.c.hoos.sr@ada95.com>
Newsgroups: comp.lang.ada
Subject: Re: Function pointer in Ada?
Date: Tue, 14 May 2002 13:24:43 -0500
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Date: 2002-05-14T13:24:43-05:00


----- Original Message -----
From: "Kai Schuelke" <kai.schuelke@gmx.net>
Newsgroups: comp.lang.ada
To: <comp.lang.ada@ada.eu.org>
Sent: Tuesday, May 14, 2002 12:58 PM
Subject: Re: Function pointer in Ada?


> Hello,
>
> I managed to get a function pointer (left, right : FLOAT) return FLOAT but
I
> couldn't manage to get a pointer to the according Standard."+". I tried
> various ways but had to use a workaround. Is it possible to do something
> like:
>
> plus_pointer : pointer_type := access Standard."+";
>
Why you would want to do this, I can't imageine, but here's how it can be
done:

First, since you are not allowed to take the 'Access attribute of an
intrinsic
function, I "wrapped" the Standard (intrinsic) function in a user-defined
function, then took the 'Access attribute of that.

The code to demonstrate it is here:

with Ada.Text_IO;
procedure Standard_Function_Access
is
   type Dyadic_Float_Access is access
     function (Left, Right : Float) return Float;
   function "+" (Left, Right : Float) return Float
   is
   begin
      return Standard."+" (Left, Right);
   end "+";
   Float_Plus_Access : constant Dyadic_Float_Access := "+"'Access;
begin
   Ada.Text_IO.Put_Line
     ("3.1 + 7.2 =" & Float'Image
      (Float_Plus_Access (3.1, 7.2)));
end Standard_Function_Access;

I also took the liberty of using "Adaesque" names for the declarations.