st$lu (6) --- internal symbol table lookup               03/23/80


            _C_a_l_l_i_n_g _I_n_f_o_r_m_a_t_i_o_n

                 integer function st$lu (symbol, node, pred, table)
                 character symbol (ARB)
                 pointer node, pred, table

                 Library:  vswtlb (standard Subsystem library)


            _F_u_n_c_t_i_o_n

                 'St$lu'  attempts  to find the character-string symbol given
                 as its first argument in  the  symbol  table  given  as  its
                 fourth argument.  If the symbol is present, a pointer to its
                 node  is  returned in 'node' and 'st$lu' returns YES; other-
                 wise, 'st$lu' returns NO.  In both cases, 'pred' is  set  to
                 the  address  of  the  link field of the previous node, i.e.
                 the one that points to the desired node (if it  is  present)
                 or is at the end of the appropriate hash chain (if it is not
                 present).

                 'St$lu'  is  not  intended for general use; the symbol table
                 interface  routines  'enter',  'lookup',  and  'delete'  are
                 provided for that purpose.


            _I_m_p_l_e_m_e_n_t_a_t_i_o_n

                 'St$lu'  hashes the character string by summing the internal
                 representations of its characters  and  then  reducing  this
                 number  modulo  the  hash table size (a prime number).  This
                 hash is used as an index into a hash table containing  heads
                 of linked lists of symbol table nodes.  The appropriate list
                 is  then searched linearly for a node containing the desired
                 symbol text.  The utility routine 'equal' is used  for  per-
                 forming string comparisons.

                 If the symbol is found, then its index and its predecessor's
                 link field index are returned, along with the function value
                 YES.   Otherwise,  the address of the last link field in the
                 appropriate chain is returned, along with the function value
                 NO.  The combination of node address/predecessor address  is
                 designed to make insertion, deletion, and updating of symbol
                 table nodes relatively easy.


            _A_r_g_u_m_e_n_t_s _M_o_d_i_f_i_e_d

                 pred, node


            _C_a_l_l_s

                 equal




            st$lu (6)                     - 1 -                     st$lu (6)




            st$lu (6) --- internal symbol table lookup               03/23/80


            _S_e_e _A_l_s_o

                 enter  (2),  lookup (2), delete (2), mktabl (2), rmtabl (2),
                 dsget (2), dsfree (2), dsinit (2), sctabl (2)






















































            st$lu (6)                     - 2 -                     st$lu (6)