[erlang-questions] Efficiency of a list construction

[Paul Barry]

Interesting response.

I'm currently working my way through both Joe's book and
Francesco/Simon's.  As this is Erlang, I'm reading the two books in
parallel (of course).

Both books talk about the efficiency of tail recursion over direct
recursion with a bit of talk about how the run-time may optimize for
code that isn't tail recursive to improve its performance.  The
suggestion seems to be that in older versions of the run-time, tail
recursion won hands down, but that nowadays this may not always be the
case.  Is there an update on this?

Of course, Joe's book suggests that the only way to *really* know is
to measure (good advice).  Using "timer:tc" (as described on page 107
of the Francesco/Simon book) might be a good place to start.

Regards.

Paul.


On 20 May 2011 11:50, Vance Shipley <vances@REDACTED> wrote:
> Kannan,
>
> No, it is not tail recursive.  This is:
>
>     %% @spec() -> [term()]
>     %%
>     flush() ->
>        flush([]).
>
>     %% @hidden
>     flush(Msgs) ->
>        receive
>                Msg ->
>                        flush([Msg | Msgs]);
>        after 17 ->
>                Msgs
>        end.
>
> On Fri, May 20, 2011 at 03:45:19PM +0530, Kannan wrote:
> }  Is the following list construction an efficient one?
> }
> }  flush() ->
> }      receive
> }  Msg ->
> }      [Msg|flush()]
> }      after 17 ->
> }      []
> }      end.
>
> --
>        -Vance
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-- 
Paul Barry, w: http://paulbarry.itcarlow.ie, e: paul.barry@REDACTED
Lecturer, Computer Networking: Institute of Technology, Carlow, Ireland.