require 'rubygems'
require 'bud'

class AtomicRegister
  include Bud

  state do
    table :write, [:wid] => [:name, :val]
    table :write_log, [:wid] => [:name, :val, :prev_wid]
    table :dom, [:wid]
    scratch :write_event, write.schema
    scratch :live, write_log.schema
  end

  bloom do
    write_event <= write.notin(write_log, :wid => :wid)
    write_log <+ (write_event * live).outer(:name => :name) do |e,l|
      e + [l.wid.nil? ? 0 : l.wid]
    end
    dom <= write_log {|l| [l.prev_wid]}
    live <= write_log.notin(dom, :wid => :wid)
  end
end