From: Patrick Hurley <phurley@...>
Date: 2006-07-14T23:24:14+09:00
Subject: Re: Recursion and Ruby

> On 7/14/06, Glenn Cadman <glenn.cadman@gmail.com> wrote:
> > The problem for
> > me is that I find it difficult to understand what is happening in this
> > code.

When I am confused (which happens all too often), I like to "see" what
is happening. Below is the same algorithm with a slightly different
implementation (I used class variables rather than a global). I also
provided a simple accessor to the class variable.

Good Luck
pth

class Integer
  @@fib = Hash.new do |h,k|
    puts "Calculate fib[#{k}]"
    h[k] = h[k-2] + h[k-1]
  end

  @@fib[0] = 0
  @@fib[1] = 1

  def fib
    @@fib[self]
  end

  def self.fibs
    @@fib
  end
end

puts 10.fib
puts 7.fib.fib
p Integer.fibs

----- Output ------
Calculate fib[10]
Calculate fib[8]
Calculate fib[6]
Calculate fib[4]
Calculate fib[2]
Calculate fib[3]
Calculate fib[5]
Calculate fib[7]
Calculate fib[9]
55
Calculate fib[13]
Calculate fib[11]
Calculate fib[12]
233
{5=>5, 11=>89, 0=>0, 6=>8, 12=>144, 1=>1, 7=>13, 13=>233, 2=>1, 8=>21,
3=>2, 9=>34, 4=>3, 10=>55}