[isection][empty] provide free function to query if isection is empty

frackit/entitynetwork/constraints.hh

@@ -31,6 +31,7 @@
 #include <frackit/distance/distance.hh>
 #include <frackit/magnitude/magnitude.hh>
 #include <frackit/intersection/intersect.hh>
+#include <frackit/intersection/emptyintersection.hh>
 #include <frackit/intersection/intersectionpredicates.hh>
 
 #include "impl_admissibledimension.hh"
@@ -176,7 +177,7 @@ public:
         const auto isection = !useIntersectionEps_ ? intersect(geo1, geo2)
                                                    : intersect(geo1, geo2, intersectionEps_);
 
-        if ( !IntersectionPredicates::isEmpty(isection) )
+        if ( !isEmptyIntersection(isection) )
         {
             // check  if dimensionality constraint is violated
             if (!allowEquiDimIS_ && !ConstraintImpl::isAdmissibleDimension(isection, dim-1))

frackit/intersection/emptyintersection.hh

@@ -24,6 +24,7 @@
 #define FRACKIT_EMPTY_INTERSECTION_HH
 
 #include <string>
+#include <variant>
 
 namespace Frackit {
 
@@ -61,6 +62,33 @@ template<int wd>
 struct IsEmptyIntersection<EmptyIntersection<wd>>
 { static constexpr bool value = true; };
 
+/*!
+ * \brief Returns true if a geometry describes an empty intersection.
+ * \tparam IsGeometry the geometry of an intersection
+ */
+template<class IsGeometry>
+constexpr bool isEmptyIntersection(const IsGeometry& is)
+{ return IsEmptyIntersection<IsGeometry>::value; }
+
+/*!
+ * \brief Overload for intersection variant
+ */
+template<class... T>
+bool isEmptyIntersection(const std::variant<T...>& intersection)
+{ return std::visit([&] (auto&& is) { return isEmptyIntersection(is); }, intersection); }
+
+/*!
+ * \brief Overload for general intersections possibly
+ *        containing possibly various types.
+ */
+template<class Geo>
+bool isEmptyIntersection(const std::vector<Geo>& intersections)
+{
+    return std::all_of(intersections.begin(),
+                       intersections.end(),
+                       [&] (const auto& is) { return isEmptyIntersection(is); } );
+}
+
 } // end namespace Frackit
 
 #endif // FRACKIT_EMPTY_INTERSECTION_HH