From: Paul Lutus <nospam@...>
Date: 2006-11-30T06:55:07+09:00
Subject: Re: One field maintaining (boolean) state of multiple items

El Gato wrote:

> I have a friend who posed a question to me about how to maintain the
> state of a few boolean values (radio buttons to be specific) in one
> (integer) database column.  It really is more of a curious question than
> anything else, as he could simply add more columns to the table to avoid
> even thinking about it, but for the sake of fun he didn't.  So, let's
> say you have three boolean values that you need to store in one field,
> and you must be able to determine what the state is (true/false) of any
> of the 3 values at any time.  How would you do this?  My immediate
> thought went to bit shifting or some other bit operations, but I've
> never really used anything like that before, so I'm a little stuck on
> this.  Thoughts?

Given an integer that you want to disassemble into binary bits:

v = 15

Let's create an array that will contain the values of the bits:

array = []

Now let's scan the integer's bits:

1.upto(8) do
  array << (v & 1 == 1)
  v >>= 1
end

Now the array contains 8 boolean (true/false) values corresponding to the
low 8 bits in the original integer.

-- 
Paul Lutus
http://www.arachnoid.com