Yesterday and today I implemented a parser for the Real Life Markup Language
(RLML) invented by Paul Battley for Ruby.
RLML aims to “Make an alternative to XML that is simple to use for
both man and machine.” You can read the provisional specification at
http://po-ru.com/rlml/rlml.txt
So far, I have programmed a very low core, non validating API
CoreParser, StreamParser, a more SAX-like streaming API, and
TreeParser, a DOM-like interface. Each of these builds on the other
ones.
For example, this XML document:
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
would look like that in RLML:
rlml/iso-8859-1
note
{
to{Tove} from{Jani} heading{Reminder}
body{Don't forget me this weekend!}
}
These are the events in CoreParser:
[:encoding, "iso-8859-1"], [:start_tag, "note"],
[:start_tag, "to"], [:idata, "Tove"], [:end_tag],
[:start_tag, "from"], [:idata, "Jani"], [:end_tag],
[:start_tag, "heading"], [:idata, "Reminder"],
[:end_tag], [:start_tag, "body"], [:idata, "Don't"],
[:idata, " "], [:idata, "forget"], [:idata, " "],
[:idata, "me"], [:idata, " "], [:idata, "this"],
[:idata, " "], [:idata, "weekend!"], [:end_tag], [:end_tag]
And this is emitted in StreamParser:
[:encoding, "iso-8859-1"], [:start_tag, "note"],
[:start_tag, "to"], [:data, "Tove"], [:end_tag, "to"],
[:start_tag, "from"], [:data, "Jani"], [:end_tag, "from"],
[:start_tag, "heading"], [:data, "Reminder"],
[:end_tag, "heading"], [:start_tag, "body"],
[:data, "Don't forget me this weekend!"],
[:end_tag, "body"], [:end_tag, "note"]
Finally, TreeParser returns this:
#<Tree: [#<Tree:note [#<Tree:to ["Tove"]>,
#<Tree:from ["Jani"]>,
#<Tree:heading ["Reminder"]>,
#<Tree:body ["Don't forget me this weekend!"]>]>]>
Building the API this way was a lot of fun, as each layer only does
its job. And yes, you can pipeline the streaming APIs. :-)
RLML is definitely a niche markup language, but it’s very easy to
implement (~280 LoC so far) and has a simple, nice, userfriendly
syntax. (It’s also possible to be converted from/to XML, with the loss
respective conversion of attribute data.)
Now, on with unit tests…
Gottseidank bin ich Atheist.
Tanz’ den Indepen-dance!
Aus Ferstls Heft: telegrap
, pone
, wich
, tings
.
NP: Pearl Jam—Bushleaguer
