set_subtract (4) --- place difference of two sets in a third  07/20/84


          | _C_a_l_l_i_n_g _I_n_f_o_r_m_a_t_i_o_n

                 subroutine set_subtract (set1, set2, destination)
                 pointer set1, set2, destination

          |      Library: vswtmath (Subsystem mathematical library)


            _F_u_n_c_t_i_o_n

                 'Set_subtract'  performs the set subtraction operation, i.e.
                 places in the set 'destination'  those  elements  of  'set1'
                 that  are  not  in  'set2'.  For proper operation, all three
                 sets should be the same size.

                 All set manipulation routines make use of  dynamic  storage,
                 which  must  be  initialized  before  use.  See 'dsinit' for
                 further information.

                 Note that all set manipulation routines have long names.  To
                 avoid unique name conflicts with other routines, any  Ratfor
                 program  using the set routines should include the following
                 statement:

          |           include "=src=/lib/math/swtmlb_link.r.i"


            _I_m_p_l_e_m_e_n_t_a_t_i_o_n

                 Since sets are represented as bit vectors,  the  subtraction
                 operation is performed by logically 'and'ing the elements of
                 the  first  set  with  the  negation  of the elements of the
                 second set.


            _B_u_g_s

                 Should work with sets of differing sizes.


            _S_e_e _A_l_s_o

                 other set routines ('set_?*') (4)















            set_subtract (4)              - 1 -              set_subtract (4)