I had played with xml/sax before, but I'd never seen xml/sax/x2j:
http://www.jsoftware.com/jwiki/Addons/xml/sax/x2j%20Examples
For others who haven't seen it, it's a compact, declarative syntax for
addressing and transforming XML paths. Think XSLT but more concise; so it
preserves the joy of J programming while providing flexibility to work
with XML (which is not an easy interface to design; J likes rectangles,
not trees).
In combination with web/httpget (another gift from my wishlist) and
regexes, J finally has the tools to express concise, precise web data
transformation. For an example, see the "Sort most popular programming
languages" task on RC:
http://rosettacode.org/wiki/Sort_most_popular_programming_languages#J
and the linked notes on the Talk page.
In the past to accomplish this sort of task, I would go through a lengthy
process using several external tools: wget (fetch) > tidy (force HTML into
XHTML) > xsltproc (address interesting data) > J (transform data). But I
won't do that anymore. In particular I won't miss XSLT, which I never got
a hang of, and was always the longest and most laborious part of the
process [1].
-Dan
[1] Of course, XSLT still has some advantages over x2j, which is built on
SAX. In particular, XSLT has a full implementation of XPath, but SAX is
limited to static, literal paths (basically because it passes you every
node and lets you decide if you're interested in it; and the x2j is simply
a more productive syntax/interface over this mechanism, which simply
compares the path of the current node to the paths you've registered
interest in).
However, I do see one potential improvement that x2j does have control
over, to wit, the need for assignment in order to build tables
(rectangles) of interest. I understand why this is neccesary in the
general case (and why it's easy to implement, given SAX's callback
nature). But I'd be interested in discussing an extension.
I envision syntacic sugar that bypassed the need for assignment and
permitted a functional description of transforming paths and sub-paths
into tables (functional at the notational level anyway, which is all
that's important). Combined with the existing compact format this
extension would allow x2j to embody the best principles of J, seamlessly
extending its reach to XML and other tree structures.
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