[erlang-questions] variable unbound

Dale Harvey <>
Thu Apr 2 13:31:50 CEST 2009


log_message(File)->
  receive
    {open,File} ->
      case file:open("File", [append]) of
        {ok,FileD} ->
          log_message(FileD);
        {error,Reason} ->
          io:format( "~s~n",[Reason])
      end;
     {data,Data} ->
        case File of
          not_open ->
            exit(oops_file_not_open);
          Else ->
           io:format(File,"~s~n",[Data]),
           log_message(File)
                end
  end.

is closer to what you are wanting, variable only have scope
within a function call, this isnt a closure, to keep a variable
in scope you pass it into the next call of the function.

2009/4/2 Robert Virding <>

> 2009/4/2 Gamoto <>
>
>> What is wrong in this function ? I receive the following error: variable
>> 'S' is unbound !
>> I also receive two warnings: File is unused, S is unused.
>> This process can receive two messages: one file to open and one message to
>> write
>>
>> Pid ! {open,"filetoopen.txt"}
>>
>> Pid ! {data, Message}
>>
>> log_message()->
>>    receive
>>                {open,File} -> case file:open("File", [append]) of
>>                                                        {ok,S} ->
>>  log_message();
>>                                    {error,Reason} -> io:format(
>> "~s~n",[Reason])
>>                                    end;
>>                {data,Data} ->  io:format(S,"~s~n",[Data]),
>>                                                  log_message()
>>   end.
>
>
> - The variable File is defined in the message {file,File} you recieve but
> is never used, you open the file "File".
>
> - The variable S is defined when you receive the {open,File} message, but
> you wish to use it when you receive the {data,Data} message where it is not
> defined.
>
> Robert
>
>
> _______________________________________________
> erlang-questions mailing list
> 
> http://www.erlang.org/mailman/listinfo/erlang-questions
>
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