MODULE midinf

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

    SUB midinf (dum, aa, bb, s, n)

        DECLARE FUNCTION inf, func     ! func is supplied by the user

        LET b = 1 / aa
        LET a = 1 / bb
        IF n = 1 then
           LET x = .5 * (a + b)
           LET s = (b - a) * inf(.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 + inf(x)
               LET x = x + ddel
               LET sum = sum + inf(x)
               LET x = x + del
           NEXT j
           LET s = (s + (b - a) * sum / tnm) / 3
           LET it = 3 * it
        END IF

        FUNCTION inf (x)
            DECLARE FUNCTION func
            LET inf = func(1 / x) / x ^ 2
        END FUNCTION

    END SUB

END MODULE