Rstructural - Ruby structural types

• Rstruct
  • Struct implemented with Ruby
• Enum
  • A set of constants
• Algebraic Data Type(ADT)
  • A set of objects
  • A object is a constant or a set of objects

Applied Types

• Option
  • Some or None
• Either
  • Left or Right

Installation

Add this line to your application's Gemfile:

gem 'rstructural'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install rstructural

Usage

require

require 'rstructural'
# Imported these types
# - Rstruct 
# - Enum 
# - ADT

or, require each modules with namespace Rstructural

require 'rstructural/struct'
# - Rstructural::Struct 
require 'rstructural/enum'
# - Rstructural::Enum 
require 'rstructural/adt'
# - Rstructural::ADT

Rstruct

module RstructSample
  # define a struct type
  Value = Rstruct.new(:value)

  puts Value.name #=> 'RstructSample::Value'
  puts value = Value.new(100) #=> 'RstructSample::Value(value: 100)
  puts value == Value.new(100) #=> true
  puts value.value == 100 #=> true
  case value
    in Value[n] # pattern match (Ruby 2.7~)
    puts "here! value: #{n}" #=> 'here! value: 100'
  else
    raise
  end
end

Enum

module EnumSample
  # define enum
  module Status
    extend Enum

    # method(:enum) creates a enum value
    OK = enum 200
    NotFound = enum 404
    InternalServerError = enum 500 do
      # add block to define custom methods
      def message
        "Something wrong"
      end
    end
  end

  puts Status::OK #=> EnumSample::Status::OK(value: 200)
  puts Status::InternalServerError.message  #=> Something wrong

  # find enum by value
  case Status.of(404)
  in Status::NotFound
    puts "NotFound!!!" #=> NotFound!!!
  else
    raise
  end
end

ADT

module AdtSample
  # define ADT
  module Shape
    extend ADT

    # define a constant object
    Point = const

    # define a object with 1 attribute
    Circle = data :radius do |mod|
      def scale(i)
        Circle.new(radius * i)
      end
      def area
        3.14 * radius * radius
      end
    end
    # define a object with 2 attributes
    Rectangle = data :width, :height do |mod|
      def area
        width * height
      end
    end

    # define common interface
    interface do 
      def is_circle?
        case self
        in Circle 
          true 
        else
          false
        end
      end
    end
  end

  puts Shape::Point #=> AdtSample::Shape::Point
  puts Shape::Rectangle.new(3, 4) #=> AdtSample::Shape::Rectangle(width: 3, height: 4)
  puts Shape::Rectangle.new(3, 4).area #=> 12
  puts Shape::Circle.new(5).scale(2).area #=> 314.0
  puts Shape::Circle.is_circle? #=> true

  case Shape::Rectangle.new(1, 2)
  in Shape::Rectangle[Integer => i, Integer => j] if j % 2 == 0
    puts "here! rectangle #{i}, #{j}" #=> here! rectangle 1, 2
  else
    raise
  end
end

Rstructural::Option

puts Option.of(100).map { |v| v * 2 } #=> Option::Some(value: 200)
puts Option.of(nil).map { |v| v * 2 } #=> Option::None
puts Option.of(100).flat_map { |v| Option.of(v * 2) } #=> Option::Some(value: 200)
puts Option.of(100).flat_map { |v| v * 2 } #=> 200
puts Option.of(nil).flat_map { |v| Option.of(v * 2) } #=> Option::None
puts Option.of(100).get_or_else { 0 } #=> 100
puts Option.of(nil).get_or_else(0) #=> 0
puts Option.of(nil).get_or_else { 0 } #=> 0
puts Option.of(nil).is_a?(Option) #=> true

Rstructural::Either

puts Either.try { 100 } #=> Either::Right(value: 100)
puts Either.try { raise "this is error" } #=> Either::Left(value: this is error)
puts Either.try { raise "this is error" }.value.inspect #=> #<RuntimeError: this is error>
puts Either.right(100).map { |v| v * 2 } #=> Either::Right(value: 200)
puts Either.left(100).map { |v| v * 2 } #=> Either::Left(value: 100)
puts Either.left(100).map_left { |v| v * 2 } #=> Either::Left(value: 200)
puts Either.right(100).flat_map { |v| Either.right(v * 2) } #=> Either::Right(value: 200)
puts Either.right(100).flat_map { |v| Either.left(v * 2) } #=> Either::Left(value: 200)
puts Either.left(100).flat_map { |v| Either.right(v * 2) } #=> Either::Left(value: 100)
puts Either.left(100).flat_map_left { |v| Either.right(v * 2) } #=> Either::Right(value: 200)
puts Either.right(100).right_or_else { 0 } #=> 100
puts Either.left(100).right_or_else { 0 } #=> 0
puts Either.right(100).left_or_else { 0 } #=> 0
puts Either.left(100).left_or_else { 0 } #=> 100
puts Either.right(100).right? #=> true
puts Either.right(100).left? #=> false

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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/petitviolet/rstruct. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

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

Code of Conduct

Everyone interacting in the Rstruct project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.