Silly Qn': Process exits at spawn

[Bengt Kleberg]

chris.danx wrote:
> Thanks folks, it runs now!
> 
> Can anyone help with another problem?  I've probably done something 
> stupid again.  The following code is supposed to query the server if a 
> neuron with the given name exists and if it does, return false.  If the 
>  neuron doesn't exist, it creates a new neuron one (a process) and 
> returns.  The problem I'm having is finding where abouts the hang 
> occurs.  Does anyone have any tips for debugging Erlang?

see the manual page for module ''dbg''.


> I think it fails to receive the {Reg, Exists} message in create neuron, 
> but I could be wrong.
> 
> 
> %% create a neuron
> %
> create_neuron (Name, State, OutputFunc) ->
>     neural_registry ! {self(), exists, Name},
>     receive
>     {Reg, Exists} -> if Exists == true ->
>                  false;
>                 true ->       
>                  {X, Pid} = neurons:create_neuron(Name, State, OutputFunc),
>                  add_neuron_to_reg ({X, Pid})
>              end
>     end.

for the sake of simplicity i think you could re-write this as:

create_neuron(Name, State, Output) ->
      neural_registry ! {self(), exists, Name},
      receive
      {_From, true} ->
                   false;
      {_From, false} ->
                   {X, Pid} = neurons:create_neuron(Name, State, Output),
                   add_neuron_to_reg({X, Pid})
               end
      end.


bengt