退出值Undef Erlang Spawn

我在運行Solus的機器上運行正常的Ubuntu Server計算機上運行以下Erlang代碼時出錯。我是Erlang的新手，不確定如何閱讀錯誤，因爲所有其他示例在錯誤代碼中只有一個函數和模塊。我有兩個文件傳感器：退出值Undef Erlang Spawn

-module(sensor). 
-export([start/2, senseAndReport/3]). 

start(WatcherPid, SensorId) -> 
    Ref = make_ref(), 
    senseAndReport(WatcherPid, SensorId, Ref). 

senseAndReport(WatcherPid, SensorId, Ref) -> 
    Measurement = rand:uniform(11), 
    if 
     Measurement == 11 -> 
      WatcherPid ! {kill, {self(), SensorId}, error}, 
      exit(error); 
     true -> 
      WatcherPid ! {Measurement, {self(), SensorId}, Ref} 
    end, 
    receive 
     {ok, Ref} -> 
      Sleep_time = rand:uniform(10000), 
      timer:sleep(Sleep_time), 
      senseAndReport(WatcherPid, SensorId, Ref) 
    end.

體和監視器：

-module(watcher). 
-export([start/1, createSensor/3, restartASensor/2, watch/1]). 

start(NumOfSensor) -> 
    if 
     NumOfSensor == 0 -> 
      io:format("Please enter a number greater than 0.~n"); 
     true -> 
      createSensor(NumOfSensor, [], 0) 
    end. 

createSensor(NumOfSensor, SensorList, SensorId) -> 
    if 
     length(SensorList) == 10 -> 
      io:format("Start watching:~n"), 
      [io:format(" Id: ~p, Pid: ~p~n", [Id, Pid]) || {Id, Pid} <- SensorList], 
      if NumOfSensor /= 0 -> 
       spawn(watcher, createSensor, [NumOfSensor, [], SensorId]), 
       watch(SensorList); 
      true -> 
       watch(SensorList) 
      end; 
     NumOfSensor == 0 -> 
      io:format("Start watching~n"), 
      [io:format(" Id: ~p, Pid: ~p~n", [Id, Pid]) || {Id, Pid} <- SensorList], 
      watch(SensorList); 
     true -> 
      SensorPid = spawn_monitor(sensor, start, [self(), SensorId]), 
      createSensor(NumOfSensor - 1, lists:merge(SensorList, [{SensorId, SensorPid}]), SensorId + 1) 
    end. 

restartASensor(SensorList, SensorId) -> 
    {SensorPid, _} = spawn_monitor(sensor, start, [self(), SensorId]), 
    io:format(" Restarted sensor: ~p, new Pid: ~p~n", [SensorId, SensorPid]), 
    NewList = lists:merge(SensorList, [{SensorId, SensorPid}]), 
    watch(NewList). 

watch(SensorList) -> 
    receive 
     {kill, {From, FromId}, error} -> 
      io:format(" Sensor ~p died~n", [FromId]), 
      restartASensor(lists:delete({FromId, From}, SensorList), FromId); 
     {Measurement, {From, FromId}, Ref} -> 
      io:format("MSG: ~2p, From sensor ~4p~n", [Measurement, FromId]), 
      From ! {ok, Ref}, 
      watch(SensorList) 
    end.

這給我下面的輸出：

Eshell V5.8.5 (abort with ^G) 
1> c(watcher). 
{ok,watcher} 
2> watcher:start(1). 
Start watching 
    Id: 0, Pid: <0.39.0> 

=ERROR REPORT==== 18-Nov-2016::19:32:35 === 
Error in process <0.39.0> with exit value: {undef,[{rand,uniform,[11]},{sensor,senseAndReport,3}]}

來源

2016-11-19 spicelord

最近添加了'rand'模塊。你是否在Ubuntu機器上運行比Solus更早版本的Erlang？ – Dogbert

@Dogbert就是這樣！相反需要隨機。非常感謝。 – spicelord

Dogbert的評論是正確的答案。我使用的Erlang版本在Ubuntu機器上較舊，需要用隨機模塊替換rand模塊。

來源

2016-11-19 03:12:52 spicelord

退出值Undef Erlang Spawn

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