EXTERNAL

SUB golden (ax, bx, cx, dum, tol, golden, xmin)

    ! This routine has been repackaged as a subroutine
    ! since it returns two values: golden and xmin.

    DECLARE FUNCTION func         ! Supplied by the user

    LET r = .61803399
    LET c = 1 - r

    LET x0 = ax
    LET x3 = cx
    IF abs(cx - bx) > abs(bx - ax) then
       LET x1 = bx
       LET x2 = bx + c * (cx - bx)
    ELSE
       LET x2 = bx
       LET x1 = bx - c * (bx - ax)
    END IF

    LET f1 = func(x1)
    LET f2 = func(x2)
    DO WHILE abs(x3 - x0) > tol * (abs(x1) + abs(x2))
       IF f2 < f1 then
          LET x0 = x1
          LET x1 = x2
          LET x2 = r * x1 + c * x3
          LET f1 = f2
          LET f2 = func(x2)
       ELSE
          LET x3 = x2
          LET x2 = x1
          LET x1 = r * x2 + c * x0
          LET f2 = f1
          LET f1 = func(x1)
       END IF
    LOOP

    IF f1 < f2 then
       LET golden = f1
       LET xmin = x1
    ELSE
       LET golden = f2
       LET xmin = x2
    END IF

END SUB