DECLARE FUNCTION dummy! (x!)
DECLARE FUNCTION simpson! (a!, b!)
DECLARE FUNCTION integral! (a!, b!, e!)

' Main program
PRINT integral(0, 1, .001)


FUNCTION dummy (x)
    dummy = x * SQR(x)
END FUNCTION

FUNCTION integral (a, b, e)
    c = (a + b) / 2
    old.int = simpson(a, b)
    new.int = simpson(a, c) + simpson(c, b)
    IF ABS(old.int - new.int) < e THEN
        integral = (16 * new.int - old.int) / 15
    ELSE
        integral = integral(a, c, e / 2) + integral(c, b, e / 2)
    END IF
END FUNCTION

FUNCTION simpson (a, b)
simpson = (dummy(a) + dummy(b) + 4 * dummy((a + b) / 2)) * (b - a) / 6
END FUNCTION