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Think about Loose Coupling


by tlm (Prior)
on Jul 17, 2005 at 13:57 UTC ( #475560=note: print w/ replies, xml ) Need Help??

in thread Why no warnings for 1 in void context?


the lowliest monk

Re: Why no warnings for 1 in void context?
by jonadab (Parson) on Jul 18, 2005 at 11:39 UTC

    Speed was not my concern, and I certainly wouldn't quibble over a 10% speed issue. (The user generally won't even notice a speed difference until it's at least 50%.)

    The reason I am looking forward to dumping all the legacy Perl4 malarke is because of its impact on coding, especially in terms of unexpected behavior and bugginess.

    Consider, for instance, an issue we recently ran into with SVG::Metadata, as follows: this module had been using XML::Twig to parse the metadata from SVG files. (SVG is an XML format.) Bryce had set it up to use Twig's simplify method to produce a hash-reference structure, which the code in's parse routine was navigating in more or less the usual way, e.g., $metadata->{'rdf'}->{'Work'} and so forth.

    However, as we started dealing with SVG produced by different SVG editors, we found that we were running into namespace issues; some SVG might list those elements as RDF:rdf and cc:Work, for example. So we put in code, similar to the above, but with extra logic like $elt->{'rdf'} || $elt->{'rdf:RDF'} ||$elt->{'RDF'} to check for those. Oops. Do you see the problem? Neither did we, at first.

    What on earth is a pseudohash? Turns out, it's some kind of inane legacy thing from the days of yore before Perl supported references, and as a result, you aren't allowed to test for a hash key containing a colon, if it might not exist. Serious bugs result. We ended up dumping the simplify()'ed hash-reference structure entirely in favor of XML::Twig objects and their methods, like $elt->first_descendant('rdf:RDF') Granted, I'm more comfortable with the methods anyway, now that I have taken the trouble to download about half of XML::Twig's rather lengthy POD into my brain, and it does allow us to dispense with checking for optional intermediate wrapper elements, and the resulting code is probably less buggy too; nevertheless, I spent hours ironing out this issue. I seriously doubt I'm the only one ever to bang into it. Who would have thought that a hash key (which is, after all, just a string) would have issues with containing a colon? Boo, hiss.

    There are other legacy Perl4 things besides the two we've discussed in this thread. They're all going away in Perl6, and I'm glad.


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