[PD-dev] Re: symbol tables

[Mathieu Bouchard]

On Sat, 26 Mar 2005, Tim Blechmann wrote:

> still, there is one problem ... what happens, if a symbol is sent
> through an outlet, is used somewhere else in the patch and the parent
> canvas with the specific $0 symbol table is deleted ... the symbol
> pointer would point into nowhere :-( ... will have to think about this

Ok, I reviewed all my stuff again, and I can say that there is currently
no way to do what I want with the local symbols, because:

  1. There is no way to store an instance number inside of the a_type
     field of an atom, because externals discard the atom and keep
  just the t_symbol*.

  2. There is no way to store an instance number inside of a t_symbol*
     while keeping compatibility with the current code, because externals
  do dereference that pointer themselves instead of using an API, which
  means that the t_symbol* could not be replaced by
  (t_symbol*)(symbol_number*10000+canvas_number) for example.

  3. There is no way to reference-count the t_symbols because the
     externals don't indicate their reference usage to pd.

  4. There is no way to garbage-collect the t_symbols because the
     externals don't indicate to pd where are their t_symbol pointer
  variables located.

  5. Integrating the $ number into the symbol and resolving it upon
     use (instead of upon declaration) makes no sense, as it breaks
  the feature of sending the name of a local name to some
  abstraction instance, by replacing it by a behaviour that is
  very difficult to use ($1's from completely different abstractions
  would get confused for each other...)

Which means that instead the road to be taken should be to create a new
mechanism and slowly migrate everything to it, while keeping hackwards
compatibility with the current way.

The new way I am now proposing (for the first time) would introduce a new
atom type, a "pointer to variable", which would contain both a t_symbol*
and an instance number.

Am I missing anything now?

_____________________________________________________________________
Mathieu Bouchard -=- Montréal QC Canada -=- http://artengine.ca/matju