[erlang-questions] variable unbound

Gamoto <>
Thu Apr 2 15:38:22 CEST 2009


Are you sure this code is correct ?
lines 1 and 16: log_message(FileD) 
line 4: open(File, ...)

But I am newbie ... then correct me if I am wrong ...

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



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