futures.rb

include Dispatch

class Future
  def initialize(&block)
    @@queue ||= Queue.new("org.macruby.futures")
    @group = Group.new
    @@queue.async(@group) { @value = block[] }
  end
  
  def value
    @group.wait
    @value
  end
end

f = Future.new do
  sleep 2.5
  'some value'
end

p f.value