Ackermann Function by Schuyler

#!/usr/bin/python

print """This program performs Ackermann's Function, as defined by:

A(m,n) =

n+1 if m = 0

A(m-1) if m > 0 and n = 0

A(m-1, A(m, n-1)) if m > 0 and n > 0

"""

m = raw_input("Please provide a value for m: ")
n = raw_input("Please provide a value for n: ")

m = int(m)
n = int(n)

print "m = " + str(m)
print "n = " + str(n)

def is_negative(x):

if x < 0:

x = raw_input("Ackermann's function is not defined for values less than 0. Please enter a value that is greater than 0: ")

x = int(x)

if x < 0:
    
            print "Please start over with a positive value for m"
            exit()

print x

is_negative(m)

def ackermann(x,y):

#x = m 
    #y = n 
    while y > -1:

if x == 0:
        
            return y+1

elif x > 0 and y == 0:

return ackermann(x - 1, 1)

elif x > 0 and y > 0:
            
            return ackermann(x - 1 , ackermann(x, y - 1))
        
print ackermann(n,m)

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