Ruby implementation of something that looks like maybe monad.

maybe.rb

class Nothing
  def >> fn
    self
  end

  def value
    nil
  end
end

class Some
  def initialize value
    @value = value
  end

  def >> fn
    unit(fn.call(@value))
  end

  def value
    @value
  end

  protected

  def unit v
    Maybe.new(v)
  end
end

class Maybe
  def self.new value
    if value
      Some.new(value)
    else
      Nothing.new
    end
  end
end

def get_value maybe
  maybe.value
end

result0 = Maybe.new(10) >> ->(x) { x * 5 } >> ->(x) { x % 20 }
result1 = Maybe.new(nil) >> ->(x) { x * 5 } >> ->(x) { x % 20 }

puts get_value(result0) # => 10
puts get_value(result1) # => nil