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From: Preben Randhol <randhol+abuse@pvv.org>
Newsgroups: comp.lang.ada
Subject: Re: Side-Effects in Functions [Rosen Trick]
Date: Mon, 5 Nov 2001 18:11:47 +0000 (UTC)
Organization: Norwegian university of science and technology
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On Mon, 05 Nov 2001 17:42:14 GMT, Warren W. Gay VE3WWG wrote:
> 
> I think one of the issues at stake here is that Ada was meant to be
> 
> easy to read. If you allow procedures to return values, then it is
> no longer a valid assumption that what looks like a function call,
> does not produce side effects (ie. you cannot assume that the arguments
> are not modified, without looking at the declaration).

Not only that. If one allow return values in procedures one cannot know
that the procedure won't return a value unless one look at the
definition. It would make things a mess and I think it clearly would
break down readability. 

>     R := My_Function(Arg);	-- Assumed that Arg is not modified
>     R := My_Proc_Function[Arg];	-- A procedure returning.. identified by []
> 
> 
> I am not suggesting the [] make a good syntax here, but you'd have
> to do something like this to maintain the distinction that Functions
> already enjoy within Ada.

Ouch! Very bad (I think) as you then will introduce:

1. Very confusing syntax for beginners
2. Harder to "read" the difference => Lower readability
3. More easy to write wrong code. You may type [] and mean (). 
4. How should one solve dispatching?

I don't understand the need for neither function with in out nor
procedure with return values.

Preben Randhol
-- 
Please, stop bombing civilians in Afghanistan. One cannot write off
killing innocent children and other civilians as "collateral damage".
A civilian is a civilian whether he or she is American or from another
country in the world.           http://web.amnesty.org/11september.htm