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From: naasking@gmail.com (Sandro Magi)
Newsgroups: comp.lang.ada
Subject: Re: Discriminant computation problem
Date: 15 Nov 2004 06:02:39 -0800
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Date: 2004-11-15T06:02:39-08:00
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Jim Rogers <jimmaureenrogers@att.net> wrote in message news:<yjVld.906538$Gx4.504752@bgtnsc04-news.ops.worldnet.att.net>...
> You might want to reconsider your design.
> First of all, your chosen example is a very poor way to represent
> a bit vector in Ada. This appears to be an Ada translation of a C
> or C++ programming approach. 

As I said, it was just the simplest example of what I was trying to
do. It's not what I'm actually trying to do.

> My second point deals with your desire to perform a calculation
> on a parameterized value. The more acceptable way to accomplish
> such an end is the use of a generic package rather than a
> record discriminant. The use of a generic package provides
> encapsulation and information hiding for your operations that
> prevent you from unnecessarily exposing internal data structures.

I was trying to avoid the extra step of instantiating a generic
package. Furthermore, the types from one package would not be
interoperable with the types from another package would they? ie.
using my Bit_Vector example and assuming the package defines an Append
operation:

procedure Test is
  package Bit_Vector_1024 is new Bit_Vector(1024);
  package Bit_Vector_2048 is new Bit_Vector(2048);

  b1024 : Bit_Vector_1024.Bit_Vector;
  b2048 : Bit_Vector_2048.Bit_Vector;
begin
  ...
  (initialize some data in each vector)
  ...
  --this would fail to type check wouldn't it?
  Append(Data=>b1024, To=>b2048);
end Test;

Sorry for asking something so obvious, but I can't check this myself
at the moment.