' Case-sensitive binary search for a value in a SORTED array.
'
' @param  a$()    the array.
' @param  s$      the value to search for.
' @param  flags$  "i" to search case-insensitively,
' @param  lb%     the lower bound to search from,
'                 if 0/unset then search from the first element.
' @param  ub%     the upper bound to search from,
'                 if 0/unset then search from the last element.
' @return         the index of the element containing the value,
'                 or -1 if not present.
Function array.bsearch%(a$(), s$, flags$, lb%, ub%)
 Local lb_% = Max(Mm.Info(Option Base), lb%)
 Local ub_% = ub%
 If ub_% = 0 Then ub_% = Bound(a$(), 1)
 Local i%

 If InStr(UCase$(flags$), "I") Then
   Local us$ = UCase$(s$)
   Local ua$
   Do While ub_% >= lb_%
     i% = (lb_% + ub_%) \ 2
     ua$ = UCase$(a$(i%))
     If us$ > ua$ Then
       lb_% = i% + 1
     ElseIf us$ < ua$ Then
       ub_% = i% - 1
     Else
       Exit Do
     EndIf
   Loop
 Else
   Do While ub_% >= lb_%
     i% = (lb_% + ub_%) \ 2
     If s$ > a$(i%) Then
       lb_% = i% + 1
     ElseIf s$ < a$(i%) Then
       ub_% = i% - 1
     Else
       Exit Do
     EndIf
   Loop
 EndIf

 If ub_% >= lb_% Then array.bsearch% = i% Else array.bsearch% = -1
End Function