[Gm2] CAST Woes

[john o goyo]

Itzok:

Thank you for your comment. I shall first report my findings and
then explain what I was trying to do.

Izo wrote:
> john o goyo wrote:
>
> > ------------------------------------------------------------
> > 2. CASTing woes:
> >
> > Is the following not valid?
> >
> > ===[cast.mod]===
> > MODULE cast;
> >
> > FROM (*ISO*) SYSTEM IMPORT CAST, LOC;
> >
> > VAR
> >     x :LOC;
> >     n :CARDINAL;
> >
> > BEGIN (*cast*)
> >     n := 2;
> >     x := CAST(LOC, n)  (* Reported as error by GM2 of 2005-06-03 *)
> > END cast.
> > ===[cast.mod ends]===
> >
> > ------------------------------------------------------------
>
> John, have you checked the LOC with the ISO M2 standard ? I think that I 
> remember (still, I might be badly wrong ...) that the LOC has some 
> restrictions at being used as container. I think that the LOC was meant 
> to be special and used only as the input (especcially as the open array) 
> parameter in procedure definitions since it could be interpreted 
> afterwards in the procedure implementation as any given type. If I am 
> correct, already the "x : LOC" line is incorrect and not only "x := 
> CAST(LOC, n);"
>
> I think that you (and Gaius) should really check this with the standard.

================================================================
1. ISO/IEC 10514-1:1996(E)

I could find not find any such restriction (but I cannot claim to know
the entire standard #6-).  However, type FilePos in RndFile.def is
defined as an array of LOC and all the *Pos() procedures act on or
return something of this type.  I would say that restricting the use
of LOC would make it very difficult to use these procedures.


================================================================
2. Why LOC?

I was trying to compile some code that marshalled CARDINAL values
into bytes for storage and transport.  I cannot use CHAR to hold
them because the standard makes no assertion on the size of CHARs.
Other compilers accept BYTE and some even allowed something such
as "byte := cardinal MOD 256".


================================================================

> Regards, Iztok

Sincerely,
john