Re: What would you like to see in XML::LibXML ?

On Mon, 30 Jan 2012 11:38:44 +0000
Tim Brody <[email protected]> wrote:

> On Sun, 2012-01-29 at 22:11 +0200, Shlomi Fish wrote:
> > Hi Aaron,
> > 
> > On Sun, 29 Jan 2012 14:49:36 +0000
> > Aaron Crane <[email protected]> wrote:
> > 
> > > Shlomi Fish <[email protected]> wrote:
> 
> > > I'd particularly value the ability to annotate a node with a Perl
> > > scalar, and retrieve that scalar later — much like the per-node
> > > `_private` data in libxml2, but accessible to Perl code.  Straw-man
> > > API:
> > > 
> [snip]
> > Yes, it would be very tricky. One option to overcome this may be to make these
> > annotations be “tokens” which are arbitrary perl strings or numbers, but not
> > arbitrary perl scalars. The XML-LibXML programmer will be able to map or
> > unpack these tokens into something more complex, but it would be their
> > responsibility to allocate unique tokens and to free their resources later.
> > 
> > We can potentially make these annotations be dictionaries mapping «strings =>
> > strings» (using perl's built-in hashes, or balanced binary trees or whatever),
> > but I guess we can stop there. 
> > 
> > I guess that would be the case of a leaky abstraction (see
> > http://en.wikipedia.org/wiki/Leaky_abstraction , http://www.joelonsoftware.com/articles/LeakyAbstractions.html )
> > or a quirky abstraction (see http://shlomif-tech.livejournal.com/49510.html ),
> > but if it makes our life easier….
> 
> What if we overloaded the node stringification to return the memory
> address of the libxml node instead of the Perl scalar?
> 
> use overload '"' =>
> 	sub { sprintf("%s(0x%x)", ref($_[0]), $_[0]->_addr) };
> 
> Where _addr returns the pointer address of the *libxml* node (not
> proxy).
> 
> Which, I think, would allow this to work:
> $SLOW_STUFF{$node} = { ... };
> 
> This would need a big health warning about the difference between
> ref($node) and "$node".
> 

I don't like this approach too much. It raises many problems, and while being
relatively easy to implement, I would prefer to give the user the option to
annotate the node either with one datum or (preferably) with several named
values (stored in a «string => string» hash). That will be, given sufficient
support from libxml2 (like a freeing-callback), more flexible, powerful and
safer.

Regards,

	Shlomi Fish

-- 
-----------------------------------------------------------------
Shlomi Fish       http://www.shlomifish.org/
Rethinking CPAN - http://shlom.in/rethinking-cpan

Larry Wall dreams in Perl.

Please reply to list if it's a mailing list post - http://shlom.in/reply .
_______________________________________________
Perl-XML mailing list
[email protected]
To unsubscribe: http://listserv.ActiveState.com/mailman/mysubs