[Phoenix-pm] More: Coro(utine) support from the perl core

[Scott Walters]

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Date: Thu, 9 Mar 2006 15:45:12 +0100
From: Marc Lehmann <schmorp at schmorp.de>
To: perl5-porters at perl.org
Subject: Re: Coro(utine) support from the perl core
Message-ID: <20060309144512.GA22421 at schmorp.de>
References: <20060309010716.GA13267 at schmorp.de> <20060309083910.GI6272 at woobling.org>
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On Thu, Mar 09, 2006 at 10:39:10AM +0200, Yuval Kogman <nothingmuch at woobling.org> wrote:
> Please give some thought into making these serializable... I'm not

You can't, in principle, serialise those, unless you are in the same
process and keep the state, and even then, its only possible when you
ignore scoping issues.

Agni, for example, already supports continuations for use in a webserver
for a long time:

   slink "click me", {: die "You followed the link!\n" :}();

It does so by compiling all relevant code in all web server processes and
binding by md5(sourcecode). This doesn't always work (e.g. when the code
has been changed), of course, and it isn't properly scoped:

   my $var;
   slink "click me", {: $var++ :}();

Should work, but cannot, as there is no way to associate the $var inside the
{: :} with the outside $var.

This happens with simple code references already. With coroutines, it becomes
even more problematic.

The problem is simply unsolvable in _principle_, unless you throw away
some features, such as closures and the ability to load references into a
different process that saved them (which would make them rather pointless,
but would certainly be implementable in some or another form, but would
amount to simple storing of the reference for later use and serialising a
reference "ID").

The simple case can already be done using e.g. Storable.

-- 
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