[Tutor] A small (but long) introduction to recursion

[Danny Yoo]

On Wed, 25 Jul 2001, Danny Yoo wrote:

> > def addUpToNRecursive(n):
> >     if n == 0: return 0
> >     print n
> >     return addUpToNRecursive(n-1) + n
> > 
> > x = addUpToNRecursive(10)
> > print x

If it helps, try this version of the program:

###
def addUpToN(n):
    if n == 0: return 0
    print (' ' * n) + "Trying to figure out addUpToN(%s)" % n
    answer = addUpToN(n-1) + n
    print (' ' * n) + "The answer of addUpToN(%s) is %s" % (n, answer)
    return answer
###

It's a little bit longer, but it does print something pretty:


###
>>> addUpToN(5)
     Trying to figure out addUpToN(5)
    Trying to figure out addUpToN(4)
   Trying to figure out addUpToN(3)
  Trying to figure out addUpToN(2)
 Trying to figure out addUpToN(1)
 The answer of addUpToN(1) is 1
  The answer of addUpToN(2) is 3
   The answer of addUpToN(3) is 6
    The answer of addUpToN(4) is 10
     The answer of addUpToN(5) is 15
15
###