OOP_(re)

Thu, 29 May 1997 14:10:06 +0200 (MET DST)

According to Pierre Phaneuf:
> 
> According to myself (Peter Gerwinski):
> >
> > I don't like that solution either.  It makes units compiled with different
> > options *really* incompatible with each other.  (Programs using `ClassName'
> > will rely on the function returning the correct result.)
> 
> Ok, then make it a program level switch, that doesn't have any effect in
> units... But then, do we need it?

I suggest to forget about the switch and just store a pointer to a string
constant holding the name of the object in the VMT.  Since we don't need
to care about a 64k data segment (4GB will be enough for a while), these
few extra bytes are harmless.

> Its the explicit part I'm trying to avoid... I guess this part will be
> compiler dependent, but should be among very few (with the TObject.Init
> constructor).

Whatever we do here, it will be compiler dependent.  If we implement some
feature into GPC to select a constructor through a VmtLink, we can be sure
that no other compiler has this.

I do not worry about compiler dependence since all of this is written
especially for GPC - and other compilers which claim to be compatible to
GPC do not exist yet.  I *do* worry about portability between the various
platforms GPC runs on.

> > > [...] something like SetTypeOf(P, VMTLink)? ;-)
> > 
> > PtrToMyObj^.TypeOf:= TypeOf ( SomeObjectType );
> 
> Maybe this would be better... But I don't like this very much either...

What about

    AssignType ( MyObj, MyVmtLink );

where MyObj is an object variable (usually a pointer dereference) and
MyVmtLink points to the VMT?

> [...] In general, I'm
> against "magic" things, like the New() function, or the Write()/WriteLn()
> functions (in BP at least, they cannot be implemented using the
> language!).

So am I.  That's one beauty of C:  Everything, including `printf' and such,
is user-definable.  (Said by someone who is hacking a Pascal compiler because
he cannot stand the ugly syntax of C/C++ ... ;-)

    Peter

  Dipl.-Phys. Peter Gerwinski, Essen, Germany, free physicist and programmer
peter.gerwinski@uni-essen.de - http://home.pages.de/~peter.gerwinski/ [970201]
 maintainer GNU Pascal [970510] - http://home.pages.de/~gnu-pascal/ [970125]

Peter Gerwinski (peter@agnes.dida.physik.uni-essen.de)