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From: dennison@telepath.com
Subject: Re: scope and/or parameters (beginner)
Date: 1999/04/15
Message-ID: <7f59oi$tse$1@nnrp1.dejanews.com>#1/1
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Date: 1999-04-15T00:00:00+00:00
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In article <7f52vj$n90$1@nnrp1.dejanews.com>,
  Robert Dewar <robert_dewar@my-dejanews.com> wrote:
> In article <37155f01.1945002895@news.dsuper.net>,
>   fluffy_dong@dsuper.net wrote:
> > What I'm surprised about is not about a passage through a
> > single sub-program, but through two (2) of them in line,
> > two levels down.
>
> What I am surprised about is that you could think this :-)
>
> (and I read what you said ...)
>
> constant in Ada means constant, it does not mean
> "constant, except that if you call a second level procedure
> you are allowed to modify it"

I suspect he was thinking something along the lines of:
My parameters are being passed via a copy method: "in out" is copy-in-copy-out
and "in" is just copy-in. Therefore there's no harm in allowing the *copy*
inside the ourter routine to be modified, since the modification will not be
copied out.

Of course the fallacy in that is that the Ada compiler (in most cases) is
perfectly free to choose to pass those parameters by reference instead of
copy. So if you rely on the copy mechanisim in order for your algorithm to
work, you will have to do the copying youself!


--
T.E.D.

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