Question

what is the difference between recursive and iterative? thanks

Answer 1

recursive is when part of the program is running itself.
ex: squareroot(squareroot(squareroot(squareroot(99))))
iterative is running the same program over and over again.
ex:
squareroot(1)
squareroot(2)
squareroot(3)
squareroot(4)

Answer 2

I had a long exchange with a very helpful member of this group (carlsmith) who very patiently explained recursion to me. Here's a link to that long discussion:

http://openstudy.com/groups/mit+6.00+intro+computer+science+%28ocw%29/updates/4e88cecc0b8b543d41e25397#/groups/mit+6.00+intro+computer+science+%28ocw%29/updates/4e6a55580b8b4a2b95d4d5c7

Basically, a recursive function calls itself.
An iterative function works through a problem using a list, like x+1 = answer. To find the answer if x is between 1 and 100, the iterative function would test 1, then test 2, then test 3... until it got to 100 and it would stop.

Answer 3

Iteration uses (usually) a loop to repeatedly perform some task. Recursion uses a function that calls itself from within itself to implement the repitition. Here is how the factorial operation would be implemented in the two ways:

def iterativeFactorial(n):
if n < 2: return 1
product = 1
for i in range(1, n + 1):
product *= i
return product

def recursiveFactorial(n):
if n < 2: return 1
return n * recursiveFactorial(n - 1)