Erlang中的计数(如何递增变量？)

Tid = ets:new(my_counter, [public, named_table]).

ets:insert(Tid, {counter, 0}).

Increment = 1,
[{counter, OldValue}] = ets:lookup(Tid, counter),
NewValue = OldValue + Increment,
ets:insert(Tid, {counter, NewValue}).

-module(my_counter_server).
-behaviour(gen_server).

-export([start_link/0, increment/0]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
         terminate/2, code_change/3]).

start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

increment() ->
    gen_server:cast(?MODULE, increment).

init([]) ->
    {ok, 0}.

handle_cast(increment, State) ->
    {noreply, State + 1};
handle_cast(_Msg, State) ->
    {noreply, State}.

handle_call(_Request, _From, State) ->
    {reply, ok, State}.

handle_info(_Info, State) ->
    {noreply, State}.

terminate(_Reason, _State) ->
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

my_counter_server:start_link().
my_counter_server:increment().