PK_VERTEX_type_t   


typedef int PK_VERTEX_type_t;


    PK_VERTEX_type_isolated_c       isolated vertex (has no edges)
    PK_VERTEX_type_spur_c           spur vertex (single edge, one end only)
    PK_VERTEX_type_wire_c           wire vertex (all edges are wires)
    PK_VERTEX_type_normal_c         normal vertex