/**
* Report the boundary of a Set of Simplices. The boundary is a Set of facets where each facet is
* a Set of vertices <V>.
*
* @param <V> vertices (generic type V)
* @param simplexSet Set of Simplices
* @return an Iterator for the facets that make up the boundary
*/
public static <V> Set<Set<V>> boundary(final Set<? extends Simplex<V>> simplexSet) {
final Set<Set<V>> theBoundary = new HashSet<Set<V>>();
for (final Simplex<V> simplex : simplexSet) {
for (final Set<V> facet : simplex.facets()) {
if (theBoundary.contains(facet)) {
theBoundary.remove(facet);
} else {
theBoundary.add(facet);
}
}
}
return theBoundary;
}
/**
* True iff simplices are neighbors. Two simplices are neighbors if they are the same dimension
* and they share a facet.
*
* @param simplex the other Simplex
* @return true iff this Simplex is a neighbor of simplex
*/
public boolean isNeighbor(final Simplex<V> simplex) {
final HashSet<V> h = new HashSet<V>(this);
h.removeAll(simplex);
return (this.size() == simplex.size()) && (h.size() == 1);
}