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From: Kilgallen@SpamCop.net (Larry Kilgallen)
Newsgroups: comp.lang.ada
Subject: Re: What evil would happen?
Date: 12 Jul 2003 14:04:09 -0500
Organization: LJK Software
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In article <slrnbh02sj.4kj.randhol+abuse@kiuk0152.chembio.ntnu.no>, Preben Randhol <randhol+abuse@pvv.org> writes:
> Larry Kilgallen wrote:
>> Being able to return an unconstrained value along with one or more
>> constrained values from the same subprogram:
>> 
>> 	declare
>> 	    my_result : Boolean;
>> 	    my_username : constant := Parse_Username (
> 
>        my_username : constant String := ...
> 
> 
>> 		s => "SYSTEM",
>> 		result => my_result );
>> 	begin
>> 	    -- make use of that
>> 	end;
> 
> Well then functions with side effects should be more resonable than to
> make procedures into functions.
> 
> But one could also simply use a function here and return "" if the
> parsing failed and then simply check if my_username /= "".

That presumes:

	1. There is no valid meaning for returning a null username.
	2. There is no desire to return _two_ constrained values.
	3. There is no desire to return a non-Boolean constrained value.

> You have to
> do if my_result then anyway so there is really not much difference to
> the code. However I would have concidered throwing an exception in the
> case the parsing failed.

That presumes:

	4. The only use for a constrained value return is to indicate
	   failure.