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Gérard Meunier wrote:
> Douglas G. Danforth a écrit :
>> Folks,
>> Subject: Stores
>>
>> I am getting an error I can not interpret.
>> I believe I have done all of this before but
>> can not remember what I did then.
>>
>> Here is a chunk of code for which I get the warning:
>> "type is not identical with that of formal VAR-, IN- or OUT -parameter"
>>
>> Notice that there is no complaint in writing the store only in
>> reading it.
>>
>> -Doug
> Hello Doug,
>
> You must get parameter compatibility between Bits and Stores.Store
> when calling r.ReadStore(bits).
>
> An actual parameter a of type Ta is parameter compatible with a formal
> parameter f of type Tf if
> 1. Tf and Ta are equal types, or
> 2. f is a value parameter and Ta is assignment compatible with Tf, or
> 3. f is an IN or VAR parameter and Tf and Ta are record types and Ta
> is an extension of Tf.
>
> In your case, you have:
> PROCEDURE (VAR rd: Reader) ReadStore (OUT x: Store)
>
> so f (or x here) is not a value parameter and not an IN or VAR
> parameter. So only case 1 applies, and is not verified by your code.
> You should define:
>
> VAR s: Stores.Store;
>
> and write:
> r.ReadStore(s); bits := s(Bits);
>
> Cheers.
>
> Gérard
Gerard,
Thank you very much. One might think that r.ReadStore(s) would
fail since the type is not specific to Bits BUT that type information
has previously been written to the file so the system knows how
to allocate the appropriate data structure for Bits. One step
removed from the obvious but very nice in its generality.
Thanks again,
-Doug
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Received on Sat Sep 02 2006 - 23:08:10 UTC