I agree with you at the higher level. That exceptions need to be
distinguishable from non-exception errors. I am not a big fan o this
syntax though.
In this we have two levels which are passing information back. The
pmap level and the thing that is being pmapped. Both can return
values. However, I don't think the pmap level should rely on the lower
level to map its values. So we should have this return protocol at the
pmap level
{ok, _}
{error, ErrorType, _}
{exception, ExceptionType, StackInformation}
I don't think we need a special atom for the exception at all. Its
location gives it the extra specialness it needs.
Now realize that this is at the pmap level. If the lower level returns
on error, but pmap is happy could could end up with something like
{ok, {error, _}}
where error is just the return value from the pmapped function.
This is different then lists:map because lists:map run in the same
process space as the caller and in serial. An exception lists:map
behaves as expected, that is it stops all processes and does a non
local exit. There for lists:map can just directly return the value
from the called function. Our pmap can not, for the reasons described
here.
I hope this makes some sense.
On Tue, Feb 8, 2011 at 9:12 PM, Martin Logan <[email protected]> wrote:
> Guys, pmap needs to pass through exceptions. The implementation will
> be fairly straightforward, anyone against this?
>
> In the do_f function we have the line. I would change this line to
> something like
>
>
> Parent ! {self(), {error, ErrType, Error}}
>
>
> Parent ! {self(), {'$exception$', ErrType, Error}}
>
> This would be to sufficiently distinguish an exception from a passed
> back error. Right now we autoconvert exceptions into errors which does
> not look quite correct to me. There may be caveats to passing back the
> exception though and that is what I am asking you to think on. Anyhow,
> If this response above comes back into
>
> wait(Parent, Child, Timeout) ->
> receive
> {Child, Ret} ->
> Parent ! {self(), Ret}
>
> which would then be recognized there and passed back to Parent. When
> Parent receives an exception message it would rethrow it. Anyone
> wishing to collect all responses would need to catch exceptions at an
> application level. Exceptions would serve to short circuit the
> execution of any map functions in this way.
>
> Cheers,
> Martin
>
>
>
> --
> Martin Logan
> Erlang & OTP in Action (Manning) http://manning.com/logan
> http://twitter.com/martinjlogan
> http://erlware.org
>
> --
> You received this message because you are subscribed to the Google Groups
> "erlware-dev" group.
> To post to this group, send email to [email protected].
> To unsubscribe from this group, send email to
> [email protected].
> For more options, visit this group at
> http://groups.google.com/group/erlware-dev?hl=en.
>
>
--
You received this message because you are subscribed to the Google Groups
"erlware-dev" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/erlware-dev?hl=en.
