By the design of HQ, we also deal with, though not directly, problems of approximations. For each operator, we may have several implementations among which the approximate ones; thus we need a parameter for tuning between their precision and speed.
We have to deal with the differences among float, rational, real and integer computations; robustness, i.e. how to deal with exceptions; thread-safety, i.e. problems of when using threading; how to choose abstract domains using the common interface; or how to switch between the available abstract domains.
The proposed common interface for 
, New POLKA, PPL and Octagon
requires full support for every operator, thus operators being not
ready are expected to generate exceptions when they are
called. Furthermore, each library can implement and use its own
specific operators, but we do not encourage this behavior.