I've moved this question to stackoverflow
https://stackoverflow.com/questions/50573586/perl6-an-operation-first-awaited
More comments inline below.
On Tue, 29 May 2018 at 01:40, Brad Gilbert <b2gi...@gmail.com> wrote:
> .
> > An operation first awaited:
> > in sub MAIN at ./traverse-dir0.p6 line 24
> > in block <unit> at ./traverse-dir0.p6 line 5
> >
> > Died with the exception:
> > Cannot find method 'path': no method cache and no .^find_method
> > in block at ./traverse-dir0.p6 line 16
>
>
> > my $dir-read = start {
> > $dir-channel.send( $_ ) for dir $dir;
> > $dir-channel.close;
> > }
> >
> > my @workers = (^$N).map: {
> > start {
> > while my $file = $dir-channel.receive() {
> > say $file.path;
> > }
> > CATCH {
> > when X::Channel::ReceiveOnClosed { .resume }
>
> ------------------------------
>
> What did you expect to happen if you resumed?
>
> Because I expect it to try to run `say $file.path;` with invalid data.
> You can just remove the `.resume` and it works.
>
Hmm, I was expecting the resume to make $dir-channel.receive() fail and
hence the loop
while my $file = $dir-channel.receive()
to finish. That is control would not move to inside the while() loop.
It seems not :-( I'll need to get my head around what is happening.
.
> > await $dir-read, @workers;
> > }
>
> There is no need to await for $dir-read, as the workers won't finish
> until it's done anyway.
>
Yep :-)
>
> ---
>
> Anyway I would use a `react` block.
>
Nice, I'll work on this. Thanks.
My original intention was to rewrite my code with "back-pressure" on the dir()
read thread.
And then I got stuck on this error I'm posting about :-(
> my @workers = (^$N).map: {
> start react whenever $dir-channel -> $file {
> say $file.path;
> }
> }
>
> Note that `start` and `react` don't need {}, but you can use them if
> neccesary.
>
>
> my @workers = (^$N).map: {
> start {
> say 'started';
>
> react {
> say 'reacting';
>
> whenever Promise.in(½) { say '½ second has elapsed' }
>
> whenever $dir-channel -> $file {
> say $file.path;
> }
> }
> }
> }
>
