anchor.diff:           merge/1,
            get_counter/2,
            get_timestamp/2,
  +         get_entry/2,
            increment/2,
            increment/3,
            all_nodes/1,
  
positive.code:     case lists:keyfind(Node, 1, VClock) of
  	{_, {_Ctr, TS}} -> TS;
  	false           -> undefined
      end.
  
  % @doc Increment VClock at Node.
  
negative.code: -include_lib("eunit/include/eunit.hrl").
  -endif.
  
  -export_type([vclock/0, timestamp/0, vclock_node/0, dot/0]).
  
  -opaque vclock() :: [vc_entry()].
  -opaque dot() :: vc_entry().
  
  % The timestamp is present but not used, in case a client wishes to inspect it.
  -type vc_entry() :: {vclock_node(), {counter(), timestamp()}}.
  
  