[eeps] Match specs and receive

[Andras Georgy Bekes]

On Friday 11 July 2008, Richard A. O'Keefe wrote:
> Fredrik Linder asked about the possibility of
>         receive MatchSpec(X) -> ...
> and
>         function(MatchSpec(X) = V) -> ...
>
> get something that compiles 
> a MatchSpec to a recogniser 'fun' (or a receiver 'run').
>
> This may well be _better_ than putting it in the syntax,
> because it lets you use compiled (with HiPE, even native-
> compiled) code rather than interpreting MatchSpecs.
I don't know what Fredrik would use these receiver fun's, but I think 
your proposal lacks something that his can do.

With his proposal I could (just for example) write a gen_server variant 
that does not have to accept each message as they arrive, but can 
effectively do selective receive.

For example, if the handle_call function in the callback module returns
{reply, Reply, NewState, MessageSpec}

then the behavior module could receive only the "interesting" messages 
and leave everything else on the message queue, while it could, --- at 
the same time --- receive system messages, etc. as well.

So the point is that if matchspecs are allowed in receives, then they 
can be combined with "normal" patterns and with other matchspecs.

	Georgy