Re: [Caml-list] xpath or alternatives

[Richard Jones <rich@annexia.org>]

On Wed, Sep 30, 2009 at 01:00:15AM +0200, Mikkel Fahnøe Jørgensen wrote:
> In line with what Yaron suggests, you can use a combinator parser.
> 
> I do this to parse json, and this parser could be adapted to xml by
> focusing on basic syntax and ignoring the details, or you could
> prefilter xml and use the json parser directly.
> 
> See the Fleece parser embedded here:
> 
> There is also the object abstraction that dives into an object
> hierarchy after parsing, see the Objects module. The combination of
> these two makes it quite easy to work on structured data, but 3 lines
> only come after some xml adaptation work - but you can see many
> one-liner json access in the last part of the file.
> 
> http://git.dvide.com/pub/symbiosis/tree/myocamlbuild_config.ml
> 
> Otherwise there is xmlm which is self-contained in single xml file,
> and as I recall, has some sort of zipper navigator. (I initially
> intended to use it before deciding on the json format):
> 
> http://erratique.ch/software/xmlm

It's interesting you mention xmlm, because I couldn't write
the code using xmlm at all.

The discussion here has got quite theoretical, but it's not helping
me to write the original 3 lines of Perl in OCaml.

    my $p = XML::XPath->new (xml => $xml);
    my @disks = $p->findnodes ('//devices/disk/source/@dev');
    push (@disks, $p->findnodes ('//devices/disk/source/@file'));

My best effort, using xml-light, is around 40 lines:

http://git.et.redhat.com/?p=libguestfs.git;a=blob;f=ocaml/examples/viewer.ml;h=ef6627b1b92a4fff7d4fa1fa4aca63eeffc05ece;hb=HEAD#l322

Rich.

-- 
Richard Jones
Red Hat