Challenge: Binary Search.

[Moneo]

I guess it's time I posted my old code for doing a binary search.

Code:

REM "BINSER" BINARY SEARCH SUBROUTINE. Edward F. Moneo 02-Jun-89.
REM
REM  CALLING SEQUENCE:
REM         BSTAB() = Name of the table to be searched.
REM               Z = Number of entries in table.
REM           BSARG = Search argument.
REM
REM  ON OUTPUT:   Z = Found table index, (Z=0=Not found)

BINSER:
  IF Z=0 THEN RETURN
  ZTOP=0                      'Pointer to the top -1
  ZBOT=Z+1                  'Pointer to the bottom+1
  IF Z=1 THEN               'Set increment (table offset)
     ZINC=1                    
  ELSE
     ZINC=Z/2
  END IF

  DO
      Z=ZTOP+ZINC
      IF BSTAB(Z)=BSARG THEN RETURN
      IF BSTAB(Z) < BSARG THEN
         ZTOP=ZTOP+ZINC
      ELSE
         ZBOT=ZTOP+ZINC
      END IF
      ZINC=ZINC/2
      IF ZINC=0 THEN ZINC=1
  LOOP WHILE ZTOP+ZINC < ZBOT

  Z=0
RETURN

*****