A gem for solving arbitrary constraint satisfaction problems (CSPs). If the constraints are hard (as opposed to flexible/soft) and can be specified in the Ruby programming language, then this library can find a solution.


Add this line to your application's Gemfile:

gem 'csp-solver'

And then execute:

$ bundle

Or install it yourself as:

$ gem install csp-solver


# first we need to set up a Problem
problem = CSP::Solver::Problem.new
# then we need to set up some variables and their domain
weekdays = %i(monday tuesday wednesday thursday friday saturday sunday)
meals = %w(bread cheese potatoes)
problem.vars weekdays, meals
# then we set up constraints as predicate blocks
problem.all_pairs(weekdays) { |a, b| a != b}
# (or you can use the convenience method `all_different`)
# problem.all_different(weekdays)
# then it's as simple as calling #solve
# which returns to us a hash of variables as keys, and
# domain entries as values
# => { weekday: meal }

See also: Official documentation and API


This project makes uses git-flow conventions: the master branch is intended for the current stable release. Active development commits should be made on the develop branch or, better yet, on feature/ branches that will merge back into develop.

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 (CSP::Solver::VERSION) in lib/csp/solver/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.


Bug reports and pull requests are welcome on GitHub at https://github.com/komputerwhiz/csp-solver. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


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