Re: Question about programming techniques

[Andreas Kostyrka <andreas ag or at>]

On Fri, 26 Jun 1998, Andrew V. Shuvalov wrote:

> Hi!
> 
> > STL forbids mixed-type containers. That, IMHO, disqualifies it from
> > consideration for serious projects.
> 
>    How you believe it may be possible to store mixed-type containers?
> STL store objects from templates. When you store, say, a vector of < T >, all
> objects are stored in memory in sequence, not by pointers. So all objects
> must be of the same type and size.
That's an basic problem with C++.
C++ allows clients to use the size of an object, which is basically
broken, as the size of an object depends upon it private
implemantation.

Consider this one:
ObjectArray a = [ObjectArray with ("A String:", 
                                   [ObjectArray with ("1","2")])];
[[[stdio err] print a] nl];

Works like a charm in TOM ;)
(Ok the default output way is rather debug oriented, and outputs
 it a bit lispish in my eyes. But then in TOM I may reimplement
 all write methods even from the standard library even the application
 without touching the library source ;) )

> But ok, in general, when you need polymorphism, say, to store some objects
> that are similar by all operations, that means that you may use base class
> and virtual functions.
What if the class hierarchy is in an library without source, so I cannot
change it's hierarchy to include a ``do-something-method''?
(And the without source somehow applies to GPL stuff to: The
 do-something-method may be completly application specific: So
 what do you do: change the general library? bad idea.
 copy the library, patch it, and track all new versions? bad idea.
 kludge around it? probably the most often used solution.)

> Example: if you use GTK--, you may create the vector of < Gtk_Widget * > (
> vector of pointers ) and store there avery kind of widgets. Sure, you can't
> store Widgets in vector by value. If you mean this when you speak about
> restrictions, ok, i agree.
It's not really an restriction: It basically makes no sense
to copy GtkWidgets. (How does it look at the screen? two buttons for
some time?)

Andreas