Lalka

Lalka is a ruby implementation of a Task monad (aka Continuation monad) - usefull abstraction for managing parallel and concurrent code.

Usage

Create:

  task = Lalka::Task.new do |t| # block is not executed untill fork or fork_wait is called
    t.resolve(value) # resolve task to a value
    # or
    t.reject(error) # reject task with an error
    # or
    t.try { 100 } # will resolve
    # or
    t.try { raise 'error' } # will reject
  end

Create with predefined state:

  resolved_task = Lalka::Task.resolve(value) # task which resolves to a value
  rejected_task = Lalka::Task.reject(error) # task which rejects to a value
  task = Lalka::Task.try { 100 } # will resolve
  task = Lalka::Task.try { raise 'error' } # will reject

fork:

  # executes computation, fork is nonblocking, returns nil
  task.fork do |t|
    t.on_success do |value|
      # do something with a value
    end

    t.on_error do |error|
      # handle error
    end
  end

fork_wait:

  # executes computation, fork_wait blocks and returns Either from "dry-monads" gem
  task = Lalka::Task.resolve(100)

  result = task.fork_wait

  result # Right(100)

  task = Lalka::Task.reject('error')

  result = task.fork_wait

  result # Left("error")

map:

  task = Lalka::Task.resolve(99).map { |v| v + 1 }.map { |v| v.to_s + "!" }

  result = task.fork_wait
  result # Right("100!")

  task = Lalka::Task.reject('error').map { |v| v + 1 }.map { |v| v.to_s + "!" }

  result = task.fork_wait
  result # Left("error")

bind:

  task = Lalka::Task.resolve(99).bind { |v| Lalka::Task.resolve(v + 1) }

  result = task.fork_wait
  result # Right(100)

ap:

  task = Lalka::Task.resolve(-> (v) { v + 1 }).ap(Lalka::Task.resolve(99))

  result = task.fork_wait
  result # Right(100)

  task1 = Lalka::Task.resolve(99)
  task2 = Lalka::Task.resolve(1)

  result = task1.map { |x| -> (y) { x + y } }.ap(task2).fork_wait
  result # Right(100)

  result = Lalka::Task.resolve(-> (x) { -> (y) { x + y } }).ap(task1).ap(task2).fork_wait
  result # Right(100)

  result = Lalka::Task.resolve(-> (x, y) { x + y }.curry).ap(task1).ap(task2).fork_wait
  result # Right(100)

Installation

Add this line to your application's Gemfile:

gem 'lalka'

And then execute:

$ bundle

Or install it yourself as:

$ gem install lalka

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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/v-shmyhlo/lalka. 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.

License

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