[PD-dev] local symbol tables

[Tim Blechmann]

hi all ...

there was the discussion about local symbol tables some time ago.

local symbol tables (symbol tables for each parent canvas) would have
two advantages:
- faster access to symbol pointers (gensym)
- freeing unused symbols after closing the specific parent canvas

there would be an easy way to implement local symbol tables, when we
don't take the second point into account:
when deleting a parent canvas, we can be sure, that the $0 value of this
specific canvas will not be valid any more (so no symbols starting with
this specific $0 value will be created any more), unless:
- someone stores this $0 values somewhere in his patch
- we have an overflow of $0 values (not sure, if there is anything
  concerning this implemented at the moment ...)

so i'd propose this:
- every parent canvas will have a local symbol table for symbols
  starting with $0
- when deleting a parent canvas, the symbols from the local symbol table
  will be moved to a data structure containing all cleaned symbols 
  (so we won't need to garbage collect the symbols from pd/externals)
- gensym would have to be adapted to allow three kinds of behaviours:
	- normal symbol handling, using the global hash table
	- active $0 handling, adding the symbol to the specific local hash
	  table
	- obsolete $0 handling, adding symbol to the data structure 
	  containing cleaned symbols

i consider this more elegant than the current 11bit hash table ... but 
i'd like to hear some thoughs about this proposal ...

cheers .... tim


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