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

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

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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