[PPL-devel] To represent z->Empty and w->Universe.

[Zell]

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".
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