Hello,
I still have a superficial question.
Consider the domain D:= Var-> Interval, where "Interval" contains two special intervals, " Empty " and " Universe " . I am now using Int_64 from PPL to model this domain. However I feel confused when I need to represent elements that " mixes the 'Empty' and 'Universe' " . One such element is, { x->[3,5], y->[4,7], z->empty, w->universe}.
I find that, whenever a constraint like "z->empty" is added to a constraints_system, the constraints_system becomes "false". This seems reasonable because the constraint_system in PPL models a conjunction of constraints and thus one constraint is false make the whole constraint system unsatisfiable. However, I do not see how to represent elements like the one given above that mixes 'z->Empty' and 'w->Universe' . ( I would like to use 'z->empty' to mean 'z is not yet initialized', and 'w->universe' to mean that 'w is unknown' .)
I probably misunderstand something basic here. What do you think?
Thanks. Zell.
p.s Due to the help of Enea and Roberto, I am not able to use PPL in my analysis. I really appreciate your help!!! By the way, I have been using the pseudo name "Zell" because I used to write my name as "Zell". For information, my passport name is "Zhoulai", which can be more or less pronounced as "zell".