"Piers Cawley" <[EMAIL PROTECTED]> wrote
> Threads and Progress Monitors
> Dave Whipp had some more thread questions, and wondered what would be
a
> good Perl 6ish way of implementing a threaded progress monitor. Whilst
> the discussion of all this was interesting, I'm not sure that it's
> really much to do with the language, more something that one would
> implement according to taste and the particular requirements of a
given
> project.
A quick summary of what came out of it:
On the basis that perl makes simple things simple, we drilled down on the
example of a simple progress monitor. This morphed into the question of how
to implement a timeout:
sub slow
{
TIMEOUT(60) { throw TimeoutException }
# TIMEOUT(60) { return undef but reason("timeout") }
... # slow stuff, maybe calls out to 3rd-party code
return ...;
}
The implementation of the TIMEOUT macro proposed a Timer object. It was
_assumed_ that Perl6 would provide a signaling mechanism to allow such timer
objects to be implemented. $SIG{ALRM} probably isn't sufficient -- perhaps
timers will actually be parrot-level concepts. Precisely how such a
mechanism would work is unresolved.
Second, it requires the timeout block to be able to kill off the mainline of
execution, but in a way that cleans up nicely and allows execution to resume
at the caller of the timed-out block. The more general case is that one
thread may wish to inject an exception into another -- again, this assumes
some form of inter-thread signaling machanism.
Dave.
