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From: Stefan Lucks <lucks@th.informatik.uni-mannheim.de>
Newsgroups: comp.lang.ada
Subject: Re: generic function and overloading
Date: Thu, 18 Oct 2007 13:30:05 +0200
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Date: 2007-10-18T13:30:05+02:00
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> I have a few "hardware" types, for example uint16 and uint32. And I
> want to write a functions that will set or clear bits of such types.

> [...] I can define a generic Bit_Set, but then I have to
> specialize it for uin16 and uint32 with different function names.

I don't think so, see the example below:


--begin example
with Ada.Text_IO;

procedure X is

    generic
       type Swap_Type is private;
    procedure Gen_Swap (X,Y: in out Swap_Type);

    procedure Gen_Swap (X,Y: in out Swap_Type) is
       Tmp: Swap_Type:= X;
    begin
       X := Y;
       Y := Tmp;
    end Gen_Swap;

    type U_Int_8  is mod 2**8;
    type U_Int_16 is mod 2**16;
    type U_Int_32 is mod 2**32;

    procedure Swap is new Gen_Swap(U_Int_8);
    procedure Swap is new Gen_Swap(U_Int_16);
    procedure Swap is new Gen_Swap(U_Int_32);

    I,J: U_Int_8  := 255;
    S,T: U_Int_16 := 255;

begin
      J := J + 1;
      T := T + 1;
      Swap(I,J);
      Swap(S,T);
      if I >= J then
         Ada.Text_IO.Put_Line("Error for U_Int_8.");
      elsif S <= T then
         Ada.Text_IO.Put_Line("Error for U_Int_16.");
      else
         Ada.Text_IO.Put_Line("Everything fine, as expected!");
      end if;
end X;

-- end example

Now, if you change "Gen_Swap" into "Swap", you get an error message. 
Perhaps you got a similar error message and was puzzled by this.

So long

Stefan

-- 
Stefan Lucks      (moved to Bauhaus-University Weimar, Germany)
 		       <Stefan.Lucks at medien.uni-weimar.de>
------  I  love  the  taste  of  Cryptanalysis  in  the  morning!  ------