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From: "Mark A. Biggar" <mark@biggar.org>
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Newsgroups: comp.lang.ada
Subject: Re: Ideas for Ada 200X
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Date: 2003-05-30T02:38:35+00:00
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Robert A Duff wrote:
> Wesley Groleau <wesgroleau@despammed.com> writes:
> 
> 
>>>Well, I like the idea of an increment operation, and my reasoning has
>>>nothing to do with typing.  The problem is code duplication: you have to
>>>write "I" twice in "I := I + 1;".  No big deal if it's just "I", but it
>>>could be a complicated name, so the reader has to careful compare the
>>>text, and also worry about whether the name has side effects.
>>
>>What kind of entity is able to have side-effects AND to be incremented?
> 
> 
> I'm thinking of something like:
> 
> Some_Array[Get_Next_Position] := Some_Array[Get_Next_Position] + 1;
> 
> where Get_Next_Position is a function that increments the current
> position and returns it.  You can say "so don't do that", but it's
> allowed in Ada, and when I read the code, I have to think about whether
> this sort of thing is going on.

Even that case isn't too bad, but if you have a really long expression
you can always use (using your example):

declare
	x: same_as_Some_Array_element_type
		renames Some_Array[Get_Next_Position];
begin
	x := x + 1;
end;

This of course doesn't work if your expression has side-effects or
contains the exaluation of a non-pure function (like your example).
But note that even the += assignment operator in C++ doesn't work
correctly in that case either.