On 14 Aug 2017, at 18:53, Enea Zaffanella <zaffanella@cs.unipr.it> wrote:

Hello.

The Pointset_Powerset domain has a difference_assign operator.
If I remember correctly, when instantiated to used NNC_Polyhedron,
the operator should be precise.

For instance:

pset1 = { A >= 0 }
pset2 = { B = 0, A = 0 }
pset1.difference_assign(pset2) = { A >= 0, B > 0 }, { A >= 0, -B > 0 }, { B = 0, A > 0 }

Examples of its use (in the C++ interface) can be seen in

   tests/Powerset/difference1.cc

where, however, it is instantiated with the C_Polyhedron class.

As for the Prolog interface, this should be the foreign predicate to call:

extern "C" Prolog_foreign_return_type
  ppl_Pointset_Powerset_NNC_Polyhedron_difference_assign
  (Prolog_term_ref t_lhs, Prolog_term_ref t_rhs);

Let us know if it works as expected.

Cheers,
Enea.

On 08/08/2017 02:39 PM, j.c.vandepol@utwente.nl wrote:

Dear developers of PPL,

Is it possible to directly compute the set-difference of two pointset powersets?

In particular, I’m interested in the precise complement; 

convex difference approximations are not sufficient for my case.

Kind regards,

Jaco van de Pol

--

Prof. Jaco van de Pol

University of Twente (NL)

Formal Methods and Tools 

http://www.cs.utwente.nl/~vdpol

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