Re: [BLACKBOX] Reading of OUT parameters: problem solved

From: [at]} <Josef>
Date: Thu, 9 Apr 2009 09:23:44 +0200

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Content-type: text/plain

Strange!
It seems that there is no difference between OUT and VAR
except that pointers are set to NIL at procedure entry.
This is kind of strange because IN params are read-only.
So, for symmetry, one would expect OUT params
to be write-only.
At first, it looks like a bug in the compiler.
But the language report is also unsymmetric and does not state
that OUT params are write-only.

I guess that in the initial CP design OUT params were supposed
to be write-only indeed, but there have been some detail problems in
the implementation that prevented this approach.

- JT


----- Original Message -----
From: "Rainer Neubauer" <rainer.neubauer{([at]})nowhere.xy
To: <BLACKBOX{([at]})nowhere.xy
Sent: Wednesday, April 08, 2009 7:42 PM
Subject: [BLACKBOX] Reading of OUT parameters: problem solved


> Alexander,
> thanks for clarification of things.
>
> I unfortunately had a very tricky problem which took plenty of time
> for debugging today.
> Right now I suceeded in tracking down the problem to its root.
>
> Thanks again for your help :-) :-)
>
> Best regards,
> Rainer
>
> Am 08.04.2009 um 19:12 schrieb Alexander Iljin:
>
>> Hello!
>>
>> RN> thanks a lot for your instant (!!) reply :-)
>>
>> RN> So I suppose, it is possible to use OUT params as local
>> variables in
>> RN> the procedure body. Right ?
>>
>> Yes, of course. By the way, the contents of the variables is not
>> strictly undefined: pointer variables are guaranteed to = NIL on
>> procedure entry.
>>
>> ---=====---
>> Alexander
>>
>
>

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Received on Thu Apr 09 2009 - 09:23:44 UTC

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