[erlang-questions] What is the fastest way to check if a function is defined in a module?

[Metin Akat]

Thanks all. I went with the solution Richard proposed. And after testing of
the full implementation, this check is certainly not the bottleneck of the
system, as Jesper suggested.

On Tue, Mar 6, 2018 at 10:35 PM, Tristan Sloughter <t@REDACTED> wrote:

> Ooh, that looks similar, but better, to what we did in Erleans:
>
>     erlang:function_exported(Module, module_info, 0) orelse
> code:ensure_loaded(Module),
>     case erlang:function_exported(Module, FunctionName, Arity) of
>         true ->
>             erlang:apply(Module, FunctionName, Args);
>         false ->
>             Default
>     end.
>
> I guess we should likely switch to `erlang:module_loaded(M)` instead of
> checking if `module_info` is exported. Thanks!
>
> Would be nice to have it patched though :)
>
> --
>   Tristan Sloughter
>   "I am not a crackpot" - Abe Simpson
>   t@REDACTED
>
>
> On Tue, Mar 6, 2018, at 12:23 PM, Richard Carlsson wrote:
>
> I was actually considering submitting such a patch a while back, but one
> argument against making that short-cut could be that operations against the
> code server should be serialized. On the other hand I haven't yet come up
> with an example where the short-cut would make a difference that couldn't
> already happen due to processor scheduling.
>
>
>         /Richard
>
> 2018-03-06 16:40 GMT+01:00 Michał Muskała <michal@REDACTED>:
>
>
> On 6 Mar 2018, 16:36 +0100, Richard Carlsson <carlsson.richard@REDACTED>,
> wrote:
>
>
>
> is_exported(M, F, A) ->
>   case erlang:module_loaded(M) of
>     false -> code:ensure_loaded(M);
>     true -> ok
>   end,
>   erlang:function_exported(M, F, A).
>
> (code:ensure_loaded() is slow compared to the fast call to
> erlang:module_loaded(), even if the module is already in memory).
>
>
>
> I was recently wondering about this. Is there a reason
> code:ensure_loaded() does not short circuit using erlang:module_loaded()?
> It could probably even skip the request to the code server entirely in case
> the module is already loaded.
>
>
> Michał.
>
>
> *_______________________________________________*
> erlang-questions mailing list
> erlang-questions@REDACTED
> http://erlang.org/mailman/listinfo/erlang-questions
>
>
>
> _______________________________________________
> erlang-questions mailing list
> erlang-questions@REDACTED
> http://erlang.org/mailman/listinfo/erlang-questions
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20180307/3d4db318/attachment.htm>