DECLARE FUNCTION FUNC! (X!)
DECLARE FUNCTION DF! (X!)
DECLARE SUB MNBRAK (AX!, BX!, CX!, FA!, FB!, FC!, DUM!)
DECLARE FUNCTION BESSJ0! (X!)
DECLARE FUNCTION BESSJ1! (X!)
DECLARE FUNCTION DBRENT! (AX!, BX!, CX!, DUM!, DUM!, TOL!, XIMIN!)

'PROGRAM D10R4
'Driver for routine DBRENT
CLS
TOL = .000001
EQL = .0001
DIM AMIN(20)
NMIN = 0
PRINT "Minima of the function BESSJ0"
PRINT
PRINT "    Min. #       X       BESSJ0(X)   BESSJ1(X)     DBRENT"
PRINT
FOR I = 1 TO 100
  AX = I
  BX = I + 1!
  CALL MNBRAK(AX, BX, CX, FA, FB, FC, DUM)
  DBR = DBRENT(AX, BX, CX, DUM, DERIV, TOL, XMIN)
  IF NMIN = 0 THEN
    AMIN(1) = XMIN
    NMIN = 1
    PRINT USING "#######"; NMIN;
    PRINT "   ";
    PRINT USING "#####.######"; XMIN; BESSJ0(XMIN); DF(XMIN); DBR
  ELSE
    IFLAG = 0
    FOR J = 1 TO NMIN
      IF ABS(XMIN - AMIN(J)) <= EQL * XMIN THEN IFLAG = 1
    NEXT J
    IF IFLAG = 0 THEN
      NMIN = NMIN + 1
      AMIN(NMIN) = XMIN
      PRINT USING "#######"; NMIN;
      PRINT "   ";
      PRINT USING "#####.######"; XMIN; BESSJ0(XMIN); DF(XMIN); DBR
    END IF
  END IF
NEXT I
END

FUNCTION DF (X)
DF = -BESSJ1(X)
END FUNCTION

FUNCTION FUNC (X)
FUNC = BESSJ0(X)
END FUNCTION