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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: integers of 1, 2, 4 bytes
Date: Mon, 16 Jun 2014 00:55:58 +0300
Organization: Tidorum Ltd
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Date: 2014-06-16T00:55:58+03:00
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On 14-06-16 00:31 , hreba wrote:
> On 06/15/2014 04:26 PM, Stefan.Lucks@uni-weimar.de wrote:
>> On Sun, 15 Jun 2014, hreba wrote:

   [snip]

>>> Now it seems the range specification doesn't matter any more and that
>>> I could equally write
>>>
>>>  type Int16 is range -1 .. 1;
>>>  for Int16'Size use 16;
>>>  type INT is new Int16'Base;
>>>
>>> Would you really define a 16 bit integer type this way?
>>
>> Firstly, this makes your program hard to read, so this is poor software
>> engineering. Secondly, it does not do what you want it to do -- i.e., it
>> does not omit the range checks. And finally, the Ada compiler has a
>> great deal of freedom what Int16'Base actually is. While I find it hard
>> to imagine that an Ada compiler for any target machine with 2-complement
>> arithmetic would not set Int16'Base to the range -2**15 .. +2**15-1, the
>> Ada compiler might still surprise you.

I tried this on Mac OS-X, x86_64, GNAT 4.5:

   with Ada.Text_IO; use  Ada.Text_IO;

   procedure Bases
   is
      type Int16 is range -1 .. 1;
      for Int16'Size use 16;
      type INT is new Int16'Base;
   begin
      Put_Line (INT'Image (INT'First) & " .. " & INT'Image (INT'Last));
   end Bases;

The result is:

-128 ..  127


-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
      .      @       .