$CPU 8086          ' make compatible with XT systems
$LIB ALL OFF       ' turn off all PowerBASIC libraries
$ERROR ALL OFF     ' turn off all PowerBASIC error checking
$OPTIMIZE SIZE     ' optimize for smaller code
$COMPILE UNIT      ' compile to a UNIT (.PBU)
'$COMPILE EXE       ' compile to a UNIT (.PBU)

DEFINT A-Z         ' Required for all numeric functions, forces PB to not
                   ' include floating point in UNIT (makes it smaller)
'/*------------------------------------------------------------------*/
$CODE SEG "MLIB5"
'/*------------------------------------------------------------------*/
'  INDEX(NEEDLE,HAYSTACK,START)
'     Returns the position of NEELDE within HAYSTACK.  If NEEDLE is
'     not found or is a null string, 0 is returned.  If START = 0 then
'     START is set to 1.  If START > length of HAYSTACK, 0 is returned.
'     Search of HAYSTACK starts at START.
'     EXAMPLE: INDEX("day","saturday",1)   =  6
'              INDEX("x","abc def ghi",1)  =  0
'              INDEX(" ","abc def ghi",1)  =  4
'              INDEX(" ","abc def ghi",5)  =  8
'              INDEX(" ","abc def ghi",20) =  0
'/*------------------------------------------------------------------*/
    FUNCTION INDEX(BYVAL NEEDLE AS STRING, BYVAL HAYSTACK AS STRING, BYVAL S AS INTEGER) PUBLIC AS INTEGER
      IF S = 0 THEN S = 1
      XRET = 0
      IF LEN(NEEDLE) > 0 AND LEN(HAYSTACK) > 0 AND S < LEN(HAYSTACK) THEN
        XRET = INSTR(S,HAYSTACK,NEEDLE)
      END IF
      INDEX = XRET
    END FUNCTION
'/*------------------------------------------------------------------*/
'    CLS
'    PRINT INDEX("day","saturday",1);"     6                    "
'    PRINT INDEX("x","abc def ghi",1);"    0                    "
'    PRINT INDEX(" ","abc def ghi",1);"    4                    "
'    PRINT INDEX(" ","abc def ghi",5);"    8                    "
'    INPUT Z