From: Martin DeMello <martindemello@...>
Date: 2003-02-06T07:28:44+09:00
Subject: Re: a cute way to reduce a fraction?

Chris Pine <nemo@hellotree.com> wrote:
> Hello,
> 
> I'm trying to find a pretty way to reduce a fraction.  Assuming I have two
> arrays, `num' and `den', containing the prime factors of the numerator and
> the denomenator, I'd like some nice way to remove identical numbers and thus
> reduce the fraction.  So it would look like this:
> 
>  num = [2, 2, 3]  # 12
>  den = [2, 3]     #  6
> 
>  #  ...your pretty ruby here...

# Okay, not all that pretty, but

def enc(a)
  h = Hash.new(0)
  a.map {|n| "#{n}.#{h[n]+=1}"}
end

def diff(a,b)
  (enc(a) - enc(b)).map {|i| i.to_i}
end

num, den = diff(num, den), diff(den, num)

>  num  # --> [2]
>  den  # --> []

You're right, there should be a simpler way!

martin