Lamport Clock in Oz

declare
proc {Loop S Clock UpdatePort P1 P2}
   NewClock Response
in
   case S of H|T then
      if H.clock > Clock then NewClock = H.clock + 1
      else NewClock = Clock + 1 end
      {Send UpdatePort NewClock#H}
      Response = msg(clock:NewClock value:H.value+1)
      {Send P1 Response} {Send P2 Response}
      {Loop T NewClock UpdatePort P1 P2}
   end
end
fun {ClockFilter L Clock DisplayPort}
   case L of H|T then
      if Clock > H.clock then
         {Send DisplayPort H.value}
         {ClockFilter T Clock DisplayPort}
      else  H|{ClockFilter T Clock DisplayPort} end
   [] nil then nil
   end
end
proc {Display Updates Stack DisplayPort}
   case Updates of (Clock#Msg)|T then
      {Display T {ClockFilter Msg|Stack Clock DisplayPort} DisplayPort}
   end
end
proc {DumbDisplay Updates Stack DisplayPort}
   for _#Msg in Updates do {Send DisplayPort Msg.value} end
end
proc {Process Name S1 S2 P1 P2}
   Msgs MsgPort = {NewPort Msgs}
   Updates UpdatePort = {NewPort Updates}
   Displayed DisplayPort = {NewPort Displayed}
in
   thread for X in S1 do {Send MsgPort X} end end
   thread for X in S2 do {Send MsgPort X} end end
   thread {Loop Msgs 0 UpdatePort P1 P2} end
   % Replacing Display by DumbDisplay breaks the garantee that causal order
   % will be respected.
   thread {Display Updates nil DisplayPort} end
   {Browse Name(Displayed)}
end
fun {DelayStream S}
   thread
      case S of H|T then {Delay {OS.rand} mod 2000 + 500} H|{DelayStream T} end
   end
end
proc {MakeDelayPort Port Stream} Tmp in
   Port = {NewPort Tmp} Stream = {DelayStream Tmp}
end
S12 P12 {MakeDelayPort P12 S12}
S13 P13 {MakeDelayPort P13 S13}
S21 P21 {MakeDelayPort P21 S21}
S23 P23 {MakeDelayPort P23 S23}
S31 P31 {MakeDelayPort P31 S31}
S32 P32 {MakeDelayPort P32 S32}
C12 = {Connection.offer S12}
C13 = {Connection.offer S13}
C21 = {Connection.offer S21}
C23 = {Connection.offer S23}
C31 = {Connection.offer S31}
C32 = {Connection.offer S32}
{Process n1 S21 S31 P12 P13}
{Process n2 S12 S32 P21 P23}
{Process n3 S13 S23 P31 P32}
{Send P21 msg(clock:0 value:0)}