 bound of region
               (3) lower y bound of region
               (4) upper y bound of region
               (5) lower z bound of region
               (6) upper z bound of region
         bondtype
               (1) bond type
         angletype
               (1) angle type
               (2) bond type used within that angle
         remainder
               no other parameters required

assign a group of atoms or a bond type to a particular constraint
use appropriate number of coeffs for a partic