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WeightedList Build Status

WeightedList attempts to improve on the very popular weighted_randomizer gem, by:

  1. Sampling without replacement, analogous to Ruby's own Array#sample

  2. Implementing a weighted shuffle

  3. Accepting an external source of randomness for easy deterministic testing

  4. Behaving like other Ruby collections with #each, #map, #sort, etc...

Installation

Add this line to your application's Gemfile:

gem 'weighted_list'

And then execute:

$ bundle

Or install it yourself as:

$ gem install weighted_list

Usage

collection = { eastern: 150, central: 92, mountain: 21, pacific: 53 }
# This works too:
# collection = [[:eastern, 150], [:central, 92], [:mountain, 21], [:pacific, 53]]
list = WeightedList[collection]

# If you are familiar with Array#sample, none of this will surprise you:
list.sample # => :pacific
list.sample(1) # => [:central]
list.sample(3) # => [:central, :eastern, :pacific]
list.sample(100) # => [:central, :eastern, :pacific, :mountain]

# It acts like a proper Ruby collection should:
list.map(&:to_s).map(&:capitalize).sort.join(', ') # => "Central, Eastern, Mountain, Pacific"

# For when you'd like to provide your own entropy (perhaps for deterministic tests):
# Just make sure the object you pass responds to `rand`
class CustomRandomizer
  def rand(n)
    1.0
  end
end
list.sample(2, random: CustomRandomizer.new) # => [:eastern, :central]

# If you want to allow repeats:
list.sample(4, with_replacement: true) # => [:eastern, :mountain, :eastern, :eastern]

# Shuffle the list while still respecting the weights:
list.shuffle # => [:central, :eastern, :mountain, :pacific]
list.shuffle # => [:pacific, :eastern, :central, :mountain]
list.shuffle # => [:pacific, :central, :eastern, :mountain]

# If you want to mutate the original list:
list.shuffle!

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/jaysonvirissimo/weighted_list.

License

The gem is available as open source under the terms of the MIT License.

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Sample (without replacement) from and shuffle an (enumerable) weighted list

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