Merge pull request #11598 from tjhei/cell_type_hyper_cube

add ReferenceCell::Type::is_hyper_cube

diff --cc include/deal.II/grid/reference_cell.h
index 79b614d8f02f53be755a689331e85c5c5e322d7a,858e359788610bb65969c5ae6b7b35ac33a700d7..12a6b8cd407840d1e241ebc7665eb4bf416515d2
--- 1/include/deal.II/grid/reference_cell.h
--- 2/include/deal.II/grid/reference_cell.h
+++ b/include/deal.II/grid/reference_cell.h
@@@ -69,8 -69,21 +69,21 @@@ namespace ReferenceCel
      /**
       * Constructor.
       */
 -    Type(const std::uint8_t kind);
 +    constexpr Type(const std::uint8_t kind);
  
+ 
+     /**
+      * Return true if the object is a Vertex, Line, Quad, or Hex.
+      */
+     bool
+     is_hyper_cube() const;
+ 
+     /**
+      * Return true if the object is a Vertex, Line, Tri, or Tet.
+      */
+     bool
+     is_simplex() const;
+ 
      /**
       * Return the dimension of the reference cell represented by the current
       * object.