Ch8, Ex4

A very naive version

declare
fun {SlowNet3 Obj Time}
   D = {NewDictionary}
   proc {RemoveTerminatedThreads L}
      case L of X|Xr then
         if {Thread.state X}==terminated
         then {D.remove X} end
      [] nil then skip
      end
   end
in
   proc {$ M}
      Old New T = {Thread.this} in
      {RemoveTerminatedThreads {D.keys}}
      if {Not {D.member T}} then
         {D.put T {NewCell unit}}
      end
      {Exchange {D.get T} Old New}
      thread
         {Delay Time}
         {Wait Old}
         {Obj M}
         New=unit
      end
   end
end 

Note: We can't use the oz dictionary as it doesn't allow us to put result of {Thread.this} as key into it. Instead, the dictionary implementation done for Chapter-6, Ex-13 at http://ctamcp-himanshu.blogspot.com/2009/02/ch6-ex13.html is to be used.