[PD] questions

[mark]

"> Hmm - you clearly have never written an undo before.
search on google: matju undo; the first result is:
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/12752
which hints that I may have written one on 17 March 2001...
I think I'll need a vital piece of information to understand what you mean
in this paragraph."

There is a big difference in undoing changes in a object network
that undoing operations on an array. 

For example say that I have a network of externals connected 
together and I decide to delete one of them

I place the object type and location on the undo stack 
and then I put its connections on the stack because they 
have also become deleted. And here comes my first 
problem - I can't use pointers to the objects my deleted 
object was connected to because those objects may be 
deleted and restored (thus changing any pointers) - so I 
need ways of representing the network that doesn't 
rely on the way it is currently stored in memory.

Secondly are you going to restore the states of externals? 
Should a sequence object be undeleted with its internal 
state intact or is it ok to throw that away (a less than perfect 
undo but probably the only realistic choice for PD)

There are many of these problems often requiring a lot 
more information to be added to your current internal 
representation. 

Its not impossible obviously however it IS a non trivial 
task 

mark