Added first working ack.py

meshmote · meshmote · commit f66d2aab476a · 2014-10-08T19:48:47.000-07:00
diff --git a/Students/RPerkins/session02/ack.py b/Students/RPerkins/session02/ack.py
@@ -1 +1,44 @@
-def Ack(m,n):
+__author__ = 'Robert W. Perkins'
+
+
+def ack(m, n):
+    """Return the result of the Ackerman function on m and n"""
+    if m < 0 or n < 0:
+        return None
+    elif m == 0:
+        return n+1
+    elif m > 0 and n == 0:
+        return ack(m-1, 1)
+    elif m > 0 and n > 0:
+        return ack(m-1, ack(m, n-1))
+
+if __name__ == "__main__":
+    assert ack(-1, 2) == None
+    assert ack(2, -1) == None
+    assert ack(-1, -1) == None
+    assert ack(0, 0) == 1
+    assert ack(0, 1) == 2
+    assert ack(0, 2) == 3
+    assert ack(0, 3) == 4
+    assert ack(0, 4) == 5
+    assert ack(1, 0) == 2
+    assert ack(1, 1) == 3
+    assert ack(1, 2) == 4
+    assert ack(1, 3) == 5
+    assert ack(1, 4) == 6
+    assert ack(2, 0) == 3
+    assert ack(2, 1) == 5
+    assert ack(2, 2) == 7
+    assert ack(2, 3) == 9
+    assert ack(2, 4) == 11
+    assert ack(3, 0) == 5
+    assert ack(3, 1) == 13
+    assert ack(3, 2) == 29
+    assert ack(3, 3) == 61
+    assert ack(3, 4) == 125
+    #  max recursion depth exceeded after this point
+    #assert ack(4, 0) == 2**2**2-3
+    #assert ack(4, 1) == 2**2**2**2-3
+    #assert ack(4, 2) == (2**65536)-3
+    #assert ack(4, 3) == (2**2**65536)-3
+    #assert ack(4, 4) == (2**2**2**65536)-3
