"""

The idea that you can make recursive functions more efficient by making recursion the last

thing that you do.

"""

import unittest

class Solution:

def tail_recursion(self, n, result):

if n ==0:

return result

return self.tail_recursion(n-1, n*result)

class TestTailRecursion(unittest.TestCase):

def __init__(self, methodName: str = "runTest") -> None:

super().__init__(methodName)

self.sol =Solution()

def test_tail_recursion(self):

self.assertEqual(120, self.sol.tail_recursion(5,1))

self.assertEqual(24, self.sol.tail_recursion(4,1))

# if __name__=="__main__":

# unittest.main()

print("#################################")

def find_in_array(arr, target):

if not arr:

return False

elif (target ==arr[0]):

return True

else:

return (find_in_array(arr[1:], target))

print(find_in_array([1,2,4,5,8], 3))

print("################################# tail recursive implementation of factorial ################################# ")

"""

fact_tail(4) = fact_tail(4, 1)

= fact_tail(3, 4)

= fact_tail(2,12)

= fact_tail(1, 24)

= 24

"""

def fact_tail_inf(n : int, f: int):

if n <= 1:

return f

else:

return fact_tail_inf(n-1, f * n)

def fact_tail(n : int)-> int:

return fact_tail_inf(n, 1)

print("manenos:: {}".format(fact_tail(4)))

print("manenos:: {}".format(fact_tail(5)))