[Tutor] recursive function example

[Mark Lawrence]

On 10/12/2013 14:48, ugajin at talktalk.net wrote:

[snipped]

As you're clearly struggling here's my attempt at showing you what is 
happening.

c:\Users\Mark\MyPython>type mytest.py
level = 0

def mult(a, b):
     global level
     level += 1
     print('level now', level, 'a =', a, 'b =', b)
     if b == 0:
         print('immediate return as b == 0')
         return 0
     print('call mult again')
     rest = mult(a, b - 1)
     print('rest =', rest)
     value = a + rest
     print('value =', value, '(a + rest ==',a, '+', rest,')')
     return value
mult(3, 2)

c:\Users\Mark\MyPython>mytest.py
level now 1 a = 3 b = 2
call mult again
level now 2 a = 3 b = 1
call mult again
level now 3 a = 3 b = 0
immediate return as b == 0
rest = 0
value = 3 (a + rest == 3 + 0 )
rest = 3
value = 6 (a + rest == 3 + 3 )

c:\Users\Mark\MyPython>

Does this help clarify things for you?

-- 
My fellow Pythonistas, ask not what our language can do for you, ask 
what you can do for our language.

Mark Lawrence