exercise 6.5 - ack

"""==========================

exercise 6.5

=========================="""

def ack(m,n):

    if (m < 0) or (n < 0):

        print ("positive integers only please")

        return

    elif not (isinstance(m, int) and isinstance(n, int)): 

        print ("positive integers only please")

        return

    elif m == 0:

        return n+1

    elif (m > 0) and (n == 0):

        result = ack(m-1, 1)

        return result

    elif (m > 0) and (n >0): 

        result = ack(m-1, ack(m,n-1))

        return result

print (ack(3,4))