MODULE midpnt

    SHARE it, s                   ! STATIC, must be preserved between calls

    SUB midpnt (dum, a, b, s, n)

        DECLARE FUNCTION func     ! Supplied by the user

        IF n = 1 then
           LET s = (b - a) * func(.5 * (a + b))
           LET it = 1
        ELSE
           LET tnm = it
           LET del = (b - a) / (3 * tnm)
           LET ddel = del + del
           LET x = a + .5 * del
           LET sum = 0
           FOR j = 1 to it
               LET sum = sum + func(x)
               LET x = x + ddel
               LET sum = sum + func(x)
               LET x = x + del
           NEXT j
           LET s = (s + (b - a) * sum / tnm) / 3
           LET it = 3 * it
        END IF

    END SUB

END MODULE