Dear Raphael,
So, this leaves the question: would it not be a good idea to have
build-in easy-to-use module linking facilities that (i) would indeed
remember the functors it linked before, and (ii) would be as easy to
use as Module.link. In other words, should we not add something like
the definitions below to the Module functor of Mozart itself. Would
an addition as minor as this need an MEP?
Thank you!
local
ModMan = {New Module.manager init}
in
/** %% ModuleLink is like Module.link except that multiple calls
of ModuleLink share the same module manager (and don't create new
managers as Module.link does). For instance, when ModuleLink links
multiple functors which refer to a stateful datum in some functor,
then all refer to the same datum instance. By constrast, linking
with Module.link results into multiple stateful datum instances.
%% */
fun {Link2 UrlVs}
{Map UrlVs fun {$ Url}
{ModMan link(url:Url $)}
end}
end
/** %% ModuleApply is like Moduel.apply expect that it always
uses the same module manager (cf. ModuleLink).
%% */
fun {Apply2 UFs}
{Map UFs fun {$ UF}
case UF of U#F then
{ModMan apply(url:U F $)}
else
{ModMan apply(UF $)}
end
end}
end
end
Best
Torsten
On 29 Jun 2009, Raphael Collet wrote:
You are completely right. I was confused by the definition, too.
The point
of Module.link is to handle properly modules that have coreferences or
cycles in their imports.
If you want to link every functor at most once, you should create a
module
manager, and always link with that module manager.
On Mon, Jun 29, 2009 at 6:42 PM, Torsten Anders <torsten.anders at
plymouth.ac.uk> wrote:
> On 29 Jun 2009, at 14:08, Raphael Collet wrote:
>
> Module.link takes a URL as an argument, and guarantees that
several calls
> to it with the same URL will only apply the corresponding functor
once. So,
> provided that you don't refer to a given functor with distinct
URLs, it will
> never be applied more than once with Module.link.
>
>
> It appears there is some misunderstanding here. The behaviour you
describe
> only happens if the same functor is linked multiple times in a
single call
> of Module.link -- which would indeed be a strange thing to do.
Module.link
> always creates a new module manager (
> http://www.mozart-oz.org/documentation/system/
node7.html#chapter.module),
> and a new module manager has no idea what functors have been
linked by other
> module managers.
>
> As a result, linking the same functor multiple times with
*multiple calls
> of Module.link* will result in quasi multiple instances of its
stateful
> data. That this is indeed the case is exemplified by the tutorial
example I
> mentioned in my previous mail. This behaviour is also useful if the
> definition of the functor changed. However, if this behaviour is not
> intended then it results in bugs that are *very* hard to find.
>
> What I was suggesting is a definition of Module.link/
Module.apply, where
> multiple calls of these procedures always use the same module
manager (see
> my previous mail for its definition). This approach would indeed
result in
> the behaviour you described. I suggest to have both versions as
part of
> Mozart itself.
>
> Best
> Torsten
--
Torsten Anders
Interdisciplinary Centre for Computer Music Research
University of Plymouth
Office: +44-1752-586219
Private: +44-1752-558917
http://strasheela.sourceforge.net
http://www.torsten-anders.de
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