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From: "Martin Dowie" <martin.dowie@nospam.baesystems.com>
Newsgroups: comp.lang.ada
References: <mailman.1005833842.603.comp.lang.ada@ada.eu.org>
Subject: Re: How to get a compilation error
Date: Thu, 15 Nov 2001 15:06:41 -0000
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Date: 2001-11-15T15:06:41+00:00
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"Wilhelm Spickermann" <wilhelm.spickermann@t-online.de> wrote in message
news:mailman.1005833842.603.comp.lang.ada@ada.eu.org...
Hi,

I would like to get a compilation *error*, if some compile time
constant is not suitable for the algorithm in use. Example:

Chunk_Bits : constant :=
  Integer'Min (32, System.Max_Binary_Modulus / 2);
type Check is (Checkitem1, Checkitem2);
for Check'SIZE use 1 - Integer'MIN (96 mod Chunk_Bits, 1);

The last two lines result in a compilation error, if and (I
hope) only if 96 is not a multiple of Chunk_Bits. That�s what I
want -- but it�s really ugly. Does anyone have something better?


Could try:

   type A_Valid_Range is range 0 .. 0;

   My_Check : constant A_Valid_Range :=
      A_Valid_Range (96 mod (Integer'Min (32, System.Max_Binary_Modulus /
2)));

This will probably raise a warning rather than an error though.
Some compilers will let you specify that warning are to be
treated as errors.