From: Robert Dober <robert.dober@...>
Date: 2009-08-10T04:08:26+09:00
Subject: Re: Generate binary sequences of length n?

On Sun, Aug 9, 2009 at 8:32 PM, David A. Black<dblack@rubypal.com> wrote:
> Hi --
>
> On Mon, 10 Aug 2009, Tom Best wrote:
>
>> I'm rather new to Ruby.  I feel this should be very simple, but I'm
>> having trouble:
>>
>> I'd like to write a script to work through all possible binary sequences
>> of length n.
>>
>>
>>
>> The script would work as follows:
>>
>> mylength = 4
>> resultz = binary_seq_generator(mylength)
>> puts "#{resultz}"
>>
>> #resultz, not necessarily in this order:
>>
>> ["0000","0001","0010","0011","0100","0101","0110","0111","1000","1001","1010","1011","1100","1101","1110","1111"]
>
> Try this:
>
> def binary_seq_generator(n)
>  (0...(1 << n)).map {|e| "%0#{n}d" % e.to_s(2) }
> end
>
> Doesn't necessarily roll off the fingers as readily as some Ruby
> idioms do :-) But I think all or most of what you need is there, and
> there are some interesting bits to it.
Well 1.9 has to offer some elegance here

(1<<n).times.map{ | d | "%0{n}b" % d }

HTH
Robert

-- 
module Kernel
  alias_method :λ, :lambda
end