On 2010-03-18, at 02:55 , Brett van de Sande wrote:

[...]
Yes, reuse of model data structures between sessions solving differenct 
problems would be a bad idea.

if you could say more about the model than that it is a mix of cons, array, and structure objects, it might be easier to understand what can be shared. whether between sessions solving the same problem or sessions solving different ones.