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From: west@widgit.enet.dec.com (Jim West (Stealth Contractor))
Newsgroups: comp.lang.ada
Subject: Re: Question with setting sign bit
Message-ID: <2106@shodha.enet.dec.com>
Date: 6 Dec 90 13:12:40 GMT
Sender: news@shodha.enet.dec.com
Distribution: usa
Organization: Digital Equipment Corporation
Lines: 43


In article <18172@hydra.gatech.EDU>, 
ms33@prism.gatech.EDU (Mike Sullivan,  a.k.a. Sully) writes...

> 
>  I have a problem setting the sign-bit in an integer while trying to
>  explicitly set particular bits (as opposed to storing a negative
>  value.)  The problem seems to caused by the strong typing of Ada in
>  conjunction with a limitation of the compilor.  Ada wants me to use
>  unsigned integers.  The compilor I use does not have unsigned integers
>  because the processor does not support unsigned arithmetic.  I have
>  words that are coming off of a 1553 bus, and a general-purpose package
>  passing the information on to me.  I want to see if some bits are set,
>  or not set as the case may be.  There is different situation where I
> 

  Have you considered using a bit array ?  I've done this many times.  I
find it far easier to do bit twiddling this way.  An example would look
something like :

    array_size	: constant := 15

    type bit is range 0 .. 1;
    for bit'size use 1;

    type data_type is array (0 .. array_size) of bit;
    pragma pack (data_type);

    data	: data_type;

  You could then use this in conjunction with a for-use-at clause and lay
the array on top of a record, or any other data type for manipulation.

					-=> Jim <=-

----------------------------------------------------------------------
 Jim West                      |  The Schainker Converse
 west@widgit.enet.dec.com      |  to Hoare's Law :
                               |
 These are my opinions.        |   Inside every small problem
 Digital has no idea           |     is a larger problem struggling
 what I'm  saying.             |       to get out.
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