Bitset 
A fast Bitset implementation for Ruby. Available as the 'bitset' gem. This is a fork of tyler/bitset which adds the following functionality:
- Switch to Bundler's Gemspec defaults
- Bug fix for a 64 bit cardinality bug
- Adds a to_a method which returns on positions
- Adds a to_binary_array which returns fixnum 1s and 0s
- Other fixes and features are merged upstream
Installation
Usually you want to do this:
gem install bitset
But if you want the latest patches or want to work on it yourself, you may want to do this:
git clone git://github.com/brendon9x/bitset.git
cd bitset
rake build
gem install pkg/bitset-<version>.gem
Usage
You create a bitset like this:
>> Bitset.new(8)
=> 00000000
Here we created an 8-bit bitset. All bits are initialized to 0.
We can also create a bitset based on a string of ones and zeros.
>> Bitset.from_s('00010001')
=> 00010001
Obviously you can also set and clear bits...
>> bitset = Bitset.new(8)
=> 00000000
>> bitset[3] = true
=> 00010000
>> bitset[3] = false
=> 00000000
>> bitset.set(1, 3, 5, 7)
=> 01010101
>> bitset.clear(1, 5)
=> 00010001
The point of a bitset is to be, effectively, an array of single bits. It should support basic set and bitwise operations. So, let's look at a few of those.
>> a = Bitset.from_s('00001111')
=> 00001111
>> b = Bitset.from_s('01010101')
=> 01010101
>> a & b
=> 00000101
>> a | b
=> 01011111
>> b - a
=> 01010000
>> a ^ b
=> 01011010
>> ~a
=> 11110000
>> a.hamming(b)
=> 4
>> a.cardinality
=> 4
Contributing
The best way to contribute is to fork the project on GitHub, make your changes, and send a pull request. This is always much appreciated. If you want to mess around with the version numbers, gemspec, or anything like that feel free... But do it in separate commits so I can easily ignore them.
License
See LICENSE.txt.