From: Eric Christopherson <echristopherson@...>
Date: 2012-02-06T09:47:00+09:00
Subject: Re: Simple even and odd number loop in Ruby

2012/2/5 Bartosz Dziewoński <matma.rex@gmail.com>:
> I hope this is not homework. For example this would work:
>
> def f n # this function calculates next number in your sequence
>        if n % 2 == 0 # n is even
>                return n / 2
>        else
>                return n * 3
>        end
> end
>
> num = gets.to_i # read in a number
> while true # infinitely...
>        num = f(num) # find the next number
>        puts num # print it
>        sleep 1 # wait one second
> end

There's also Integer#even? and #odd?.
e.g.
if n.even?
  return n / 2
else
  return n * 3
end