Re: [Gm2] ISO SYSTEM clarification

[Iztok]

Gaius Mulley wrote:

> Hi,
>
> I'm currently implementing the ISO SYSTEM module and was wondering
> whether other compilers support SHIFT and ROTATE on non SYSTEM
> types. Ie is it permissible to:
>  

Gardens Point M2: SHIFT,ROTATE (VAR b : BITSET; n : INTEGER);

StonyBrook: SHIFT, ROTATE (set : PackedSetType; shift : INTEGER) : 
PackedSetType;

StonyBrook M2 considers sets as having a boolean membership flag for 
each value in the base type. The difference between the SET and the 
PACKEDSET (which is SBM2 extension) is that the PACKEDSET has booleans 
represented as bits while the SET elements can be realized at 
compiletime (by compiler itself) as any possible representation of the 
boolean. PACKEDSET has also determined positions of the bits inside the 
processor word regarding their basetype value.

So, the answer for your question would be - SBM2 would compile your 
example while the GPM would not. I would say that the operations would 
work for long sets also for SBM2 while I am not so sure for GPM. I would 
have to test it which I (currently) do not have time for.

Sorry for late answer - I was changing my appartement and was very very 
busy last days.

Iztok Kobal

> FROM SYSTEM IMPORT SHIFT ;
>
> VAR
>   foo: SET OF CHAR ;
>
> BEGIN
>   foo := {'a', 'b'} ;
>   foo := SHIFT(foo, 1)
> END
>
> Thanks Gaius
>
> The 4th Interim version working draft seems to restrict the type to a
> system type, whereas the iso definition modules have a more relaxed view..
>
> Gaius
>
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>  

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