From: Panagiotis Atmatzidis <atma@...>
Date: 2010-01-04T01:16:21+09:00
Subject: Few clarifications on recursion

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Hello,

I'm following C. Pine's manual for a smooth intro into ruby & =
programming. I'm just curious about this exercise which should teach =
recursion.
Here is the program sample, which as you can see is a simple factorial =
calculator:

def factorial num
  if num < 0
   return 'You can\'t take the factoria of a negative number'
  end

  if num <=3D 1
     1
  else
    num * factorial(num-1)
  end
end


Although it introduces many interesting concepts to me (i. e. I did not =
knew that after the "if" statement a single _1_ with no quotes could be =
used) I fail to see how the num changes value. The way I read the code =
here:

  num * factorial(num-1)

is 30*29 for "puts factorial(30)" not 30*29*28... which is how it works. =
I've tested the code works fine.

The book although, in my opinion is excellent (so far) for starters, =
does not explain - or it does but I did not understand it nevertheless - =
how this piece of code works.

regards

Panagiotis (atmosx) Atmatzidis

email:	atma@convalesco.org
URL:	http://www.convalesco.org
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