Ruby in XML.

< ^ > P N |<>|^_>< --- | ~ ...Help
I have just stuck this on..
   http://www.rubygarden.org/ruby?RubyInXML

I like XML.

There is a firm standard, there is a rich toolset to work on it.

I like HTML. It is simply the fastest way to deliver good looking 
documents to the widest audience.

No surprise. I like XHTML it _is_ HTML in XML. I can validate my XHTML 
documents and know that they conform exactly to the standard, and hence 
will render properly on a wide set of browsers.

I love ruby. It is quite the easiest way to program. It has a lovely XML 
API called REXML.

I sometimes need to do spreadsheet sort of things. Basically a document 
that describes my reasoning and findings, supported by numbers.

Long time ago, when I still did Perl, I found by actual trials that I was 
about as fast in Perl as the average guy is using a Spreadsheet. Sometimes 
faster, sometimes slower. But for the next hundred data sets, my perl 
scripts where a thousand times faster.

So I don't do spreadsheets these days, I write ruby scripts.

So I have taken to combining Ruby & HTML. Sometimes via cgi. It works for 
me.

But sometimes I have documents that are more HTML than ruby. So it makes 
sense to write them in HTML, with a bit of Ruby embedded. That's where erb 
and eruby live.

But I don't like erb and eruby's tags. I can't validate my XHTML.

So add REXML and I present a very small script I call rubyexml. Ruby 
Embedded in XML.

#!/usr/bin/ruby -w

require 'rexml/document'
require 'rexml/streamlistener'
require 'pp'

# All eval's are evaluated in the context of an instance of this class.
# Extend this, or add this method to a class of your own.
class Context

   def eval_value( value)
     value.gsub( %r{ \#\{ ( [^\}]+ ) \} }x) do | match|
       instance_eval( $1).to_s
     end
   end
end


# This does the work.
class Listener
   include REXML::StreamListener

   def initialize( context)
     @context = context
   end

   def comment( text)
     print @context.instance_eval( text)
   rescue SyntaxError => details
     pp @context
     pp text
     raise "Failed to compile '#{text}' in context : #{details}"
   end

   def tag_start(name,attrs)
     print "<",name
     attrs.each_pair do |key, value|
       print " #{key}=\"#{@context.eval_value( value)}\""
     end
     print ">"
   end

   def tag_end( name)
     print "</", name, ">"
   end

   def text( text)
     print @context.eval_value(text)
   end

   def cdata( ctext)
     text( ctext)
   end
end

# This comes for free from REXML. Stream parse an XML document.
REXML::Document::parse_stream( REXML::SourceFactory::create_from( STDIN), 
Listener::new( Context.new))


So take a chunk of XHTML...

<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"xhtml11.dtd" >
<html xmlns="HTTP://www.w3.org/TR/xhtml"
    xmlns:xlink="HTTP://www.w3.org/XML/XLink/0.9"
    xml:lang="en" >
    <head>
       <title>

     </title>
    </head>

    <body>
       <h1>
          The answer to life, the universe and everything is <!-- 44 - 2 
-->
       </h1>

       <p>
          The following image is   <!--  @file_name = "pretty_picture.jpg" 
-->

          <img src="#{@file_name}" alt = "#{@file_name.sub(/\.jpg/,'')}"/>
       </p>
    </body>
</html>

It validates as correct xml against the XHTML DTD.

Feed it through rubyexml and get...

<html xmlns:xlink="HTTP://www.w3.org/XML/XLink/0.9" xml:lang="en" 
xmlns="HTTP://www.w3.org/TR/xhtml">
    <head>
       <title>

     </title>
    </head>

    <body>
       <h1>
          The answer to life, the universe and everything is 42
       </h1>

       <p>
          The following image is   pretty_picture.jpg

          <img src="pretty_picture.jpg" alt="pretty_picture"></img>
       </p>
    </body>
</html>

Just so blooming simple.

And if you have a big hairy object that knows all the deeper secrets of 
life, just change rubyexml to...

REXML::Document::parse_stream( REXML::SourceFactory::create_from( STDIN), 
Listener::new( BigHairyObjectThatKnowsTheDeeperSecretsOfLife.new))

And you can refer to all it's instance variables and methods.

It all so blooming simple!



John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : john.carter / tait.co.nz
New Zealand

"At first I hoped that such a technically unsound project would
  collapse but I soon realized it was doomed to success. Almost
  anything in software can be implemented, sold, and even used given
  enough determination. There is nothing a mere scientist can say that
  will stand against the flood of a hundred million dollars. But there
  is one quality that cannot be purchased in this way---and that is
  reliability. The price of reliability is the pursuit of the utmost
  simplicity. It is a price which the very rich find most hard to
  pay." -- C.A.R. Hoare in The Emperor's Old Clothes,
           Turing Award Lecture (27 October 1980)