MODULE midsqu

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

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

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

        LET b = sqr(bb - aa)
        LET a = 0
        IF n = 1 then
           LET s = (b - a) * squ(.5 * (a + b), bb)
           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 + squ(x, bb)
               LET x = x + ddel
               LET sum = sum + squ(x, bb)
               LET x = x + del
           NEXT j
           LET s = (s + (b - a) * sum / tnm) / 3
           LET it = 3 * it
        END IF

        FUNCTION squ (x, bb)
            DECLARE FUNCTION func
            LET squ = 2 * x * func(bb - x ^ 2)
        END FUNCTION

    END SUB

END MODULE