whole_func_string: function HalfEdge(vertex, face) {
      this.vertex = vertex;
      this.prev = null;
      this.next = null;
      this.twin = null;
      this.face = face;
    }
func_code_string: function HalfEdge(vertex, face) {
      this.vertex = vertex;
      this.prev = null;
      this.next = null;
      this.twin = null;
      this.face = face;
    }
func_documentation_string: Entity for a Doubly-Connected Edge List (DCEL).