From: Ryan Leavengood <leavengood@...>
Date: 2005-11-23T07:54:11+09:00
Subject: Re: How convert an integer to a bit array

On 11/22/05, Curt Hibbs <curt.hibbs@gmail.com> wrote:
> Does anyone have a clever way to convert an integer to an array of bit
> values?
>
> For example (using 8 bit integers):
>
> 0 => [0, 0, 0, 0, 0, 0, 0, 0]
> 1 => [0, 0, 0, 0, 0, 0, 0, 1]
> 2 => [0, 0, 0, 0, 0, 0, 1, 0]
> 7 => [0, 0, 0, 0, 0, 1, 1, 1]
> etc.
>
> I was looking at Array#pack and Array#unpack to do this, but haven't figured
> it out yet. It just seems like there ought to be a simple way to do this.
>
> Anybody got a clever idea?

This way is about 4 times faster than James' version:

class Integer
  def to_ba(size=8)
    a=[]
    (size-1).downto(0) do |i|
      a<<self[i]
    end
    a
  end
end

p 0.to_ba
p 1.to_ba
p 2.to_ba
p 7.to_ba
__END__

Result:

[0, 0, 0, 0, 0, 0, 0, 0]
[0, 0, 0, 0, 0, 0, 0, 1]
[0, 0, 0, 0, 0, 0, 1, 0]
[0, 0, 0, 0, 0, 1, 1, 1]

Ryan