anchor.diff:              true;
           {ok, #variable{value=Value}} ->
               %% Already bound to same value.
  -            false;
  +            true;
           {ok, _} ->
               %% Bound, to different value.
               true;
  
positive.code:                 setup(),
                  fun teardown/0
             end,
          ?FORALL(Cmds, commands(?MODULE),
                  begin
                      {H, S, Res} = run_commands(?MODULE, Cmds),
                      ?WHENFAIL(
  
negative.code:                     {call, ?MODULE, bind, [Variable, Value, Ets]}
                  end) || length(Variables) > 0]).
  
  next_state(#state{store=Store0}=S, _V, {call, ?MODULE, bind, [Id, NewValue, _]}) ->
      %% Only update the record, if it's in inflation or has never been
      %% updated before.
      Store = case dict:find(Id, Store0) of
          {ok, #variable{type=undefined, value=undefined}=Variable} ->
              dict:store(Id, Variable#variable{value=NewValue}, Store0);
          {ok, #variable{type=undefined, value=_Value}} ->
              Store0;
          {ok, #variable{type=Type, value=Value}=Variable} ->
              case derflow_ets:is_inflation(Type, Value, NewValue) of
                  true ->
                      dict:store(Id, Variable#variable{value=Value}, Store0);
                  false ->
                      Store0
              end
      end,
      S#state{store=Store};
  next_state(#state{store=Store0}=S, V, {call, ?MODULE, declare, [Type, _]}) ->
      Store = dict:store(V, #variable{type=Type}, Store0),
      S#state{store=Store};
  next_state(S, _V, {call, ?MODULE, bind, _}) ->
      S;
  