Maybe in ruby

maybe.rb

def Maybe(obj)
  return Maybe.new(Nothing.new) if obj.nil?
  return Maybe.new(obj)
end

class Nothing
  def method_missing(*args, &block)
    self
  end

  def ==(other)
    other.is_a? Nothing
  end

end

class Maybe
	def initialize(value)
		@value = value
  end

  def nothing?
    @value.is_a? Nothing
  end
  alias :empty? :nothing?

  def value(default)
    return default if nothing?
    return @value
  end

  def else(default)
    return default if nothing?
    return self
  end
  
  def method_missing(m, *args)
    Maybe(@value.__send__(m, *args))
  end

  def ==(other)
    @value == other.instance_variable_get(:@value)
  end
end

test.rb

require 'minitest/autorun'
require_relative 'maybe'

class MaybeTest < MiniTest::Unit::TestCase
  def test_nil
    assert_equal Maybe(nil).a.b.c, Maybe(Nothing.new)
  end

  def test_some
    assert_equal Maybe("Some").downcase, Maybe("some")
  end

  def test_value_with_nil
    assert_equal Maybe(nil).a.value("foo"), "foo"
  end

  def test_value_with_some
    assert_equal Maybe("Some").downcase.value("nothing"), "some"
  end

  def test_else_with_nil
    assert_equal Maybe(nil).else("foo"), "foo"
  end

  def test_else_with_some
    assert_equal Maybe("Foo").else("bar"), Maybe("Foo")
  end
end

Please see https://github.com/pzol/monadic for a more complete implementation