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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Ideas for Ada 200X
Date: 31 May 2003 19:51:22 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2003-05-31T19:51:22-04:00
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"John R. Strohm" <strohm@airmail.net> writes:

> Should we allow, or not allow,
> 
>   J := idem;
> 
> Why or why not?  What are the semantics?

Should we allow:

    J := J;

?  The correct answer is "Who cares?".  ;-)

In any case there doesn't seem to be any big semantic difficulty here.

> In particular, consider:
> 
> DEVICE_DATA_REGISTER : BYTE;
> for DEVICE_DATA_REGISTER use at 16#4000_00F0#;
>    ...
> DEVICE_DATA_REGISTER := 16#40#;
> DEVICE_DATA_REGISTER := idem;
> DEVICE_DATA_REGISTER := idem + 1;
> 
> How many times should DEVICE_DATA_REGISTER be *read* by the above code
> fragment?  Why?

Well, there's no pragma Atomic or Volatile, so...

If there were, I would say "twice".

- Bob