Manoj Rajagopalan wrote:

Hi all

How do I check if a point is contained within a polyhedron? Firstly, how do i represent the point? in terms of X, Y, Z where these are declared to be of type Variable?

Hi.

// Supposing that you are working in a 3 dimensional space.

using namespace Parma_Polyhedra_Library;

Variable x(0); Variable y(1); Variable z(2);

// Now, create your polyhedron:

C_Polyhedron ph(3, UNIVERSE); ph.add_constraint(x + 3*y >= z) ph.add_constraint(x >= 0) ph.add_constraint(2*y +2*z <= 5)

// Then, create a point, which is a Generator, // e.g., having coordinates (1, 1, 1).

Generator g = point(x + y + z);

// Finally, compute the relation between // the polyhedron and the generator.

Poly_Gen_Relation rel = ph.relation_with(g);

// If the point is contained in the polyhedron, then // the polyhedron "subsumes" the point (i.e., adding // the point to the polyhedron won't change the polyhedron).

if (rel == Poly_Gen_Relation:subsumes()) std::cout << "The point is contained in ph" << std::endl;

Would someone have any example code snippets to illustrate related points?

thanks Manoj Rajagopalan

Have a look in ppl/tests/Polyhedron/relations1.cc, as well as the documentation for methods Polyhedron::relation_with(...).

Cheers, Enea.