spawn without linking?

Mikael Karlsson <>
Tue Apr 27 07:26:11 CEST 2004


How do you send different messages do different processes
with "!!"? 

This is is a nice feature and this is what multi_call does,
like send Req1 to Name1 and Req2 to Name2:
multi_call([{Name1, Req1}, {Name2, Req2}], Timout)

Would this become

[Name1,Name2] !! [Req1, Req]   

with bangbang? 

Regards
Mikael

Mon 26 April 2004 14:56, Joe Armstrong:
> On Thu, 22 Apr 2004, Sean Hinde wrote:
> > On 21 Apr 2004, at 04:20, Shawn Pearce wrote:
> > > Actually, it is that hard to do...  the OTP behaviors offer lots
> > > of well tested/debugging implementations which handle the border
> > > cases extremely well.  Which a naive quick implementation using
> > > just the basic spawn_link/* and trap_exit won't get quite right on
> > > the first few tries.
> > >
> > > OTP rocks for that reason alone... but yea, gen_server isn't the
> > > most "Erlang" way to write a server, but its the Erlang/OTP way.
> >
> > How about this which I had fun writing today. It is almost Erlangish,
> > and it is something like OTP, and it is exactly Joe's selective receive
> > example. I can't decide whether it is ugly or profoundly beautiful.
>
> It is of course profoundly beautiful, but the syntax obscures the beauty.
>
> Just overload the LHS of !! so you can write
>
> 	[A,B,C] !! M
>
> This means send M to three processes (machines or whatever's) and
> gather three replies yielding [V1,V2,V3]
>
> Cheers
>
> /Joe
>
> > Sean
> >
> > %% Call a bunch of gen_servers with different requests in
> > %% parallel and return successes and failures. Any which
> > %% fail to answer within Timeout ms are included as failures.
> >
> > %% We require that the calling process will continue to ignore
> > %% late answers
> >
> > multi_call(Requests, Timeout) ->
> >      Mrefs = lists:map(
> >                fun({Name, Req}) ->
> >                        Mref = erlang:monitor(process, Name),
> >                        Name ! {'$gen_call', {self(), Mref}, Req},
> >                        {Name, Mref}
> >                end, Requests),
> >      get_results(Mrefs, [], [], Timeout, now()).
> >
> > get_results([{Name, Mref}|T], Succ, Fail, Timeout, Now_at_start) ->
> >      Timeout_val = max(Timeout - (timer:now_diff(now(), Now_at_start)
> > div 1000), 0),
> >      receive
> >          {Mref, Reply} ->
> >              erlang:demonitor(Mref),
> >              receive
> >                  {'DOWN', Mref, _, _, _} ->
> >                      get_results(T, [{Name, Reply}|Succ], Fail, Timeout,
> > Now_at_start)
> >              after 0 ->
> >                      get_results(T, [{Name, Reply}|Succ], Fail, Timeout,
> > Now_at_start)
> >              end;
> >          {'DOWN', Mref, _, _, _} ->
> >              get_results(T, Succ, [Name|Fail], Timeout, Now_at_start)
> >      after Timeout_val ->
> >              erlang:demonitor(Mref),
> >              get_results(T, Succ, [Name|Fail], Timeout, Now_at_start)
> >      end;
> > get_results([], Succ, Fail, _, _) ->
> >      {Succ, Fail}.
> >
> > max(A, B) when A >= B -> A;
> > max(A, B)             -> B.



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