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If you process xml with ConTeXt Mkiv, you have the power of the Lua language at your fingertips. All <code>\xml...</code> commands have their Lua counterparts. Unfortunately, this is not yet fully documented, so this wiki page is a place-holder until Hans finishes this section in the [http://pragma-ade.comnl/show-man-43.htm Mkiv manual].

Next, we write the environment file <tt>prices-style.tex</tt> which we will use to process our list; on the command line, you use <tt>context --environment=prices-style prices.xml</tt>. As an exercise, we will use Lua for all xml elements (though this doesn't make sense in most cases). If you have already read the [http://pragma-ade.comnl/show-man-43.htm manual], most of this will be familiar. The first line connects our environment with the Lua file where all the Lua code will go. The last lines set up a ConTeXt table, since this is how we want to display the information:

What does this do? As you can see, we mostly use the <code>context...</code> commands which are described in the [http://www.pragma-ade.comnl/general/manuals/cld-mkiv.pdf cld manual]. They are Lua functions which print to ConTeXt. With the <code>list</code> function, we start a ConTeXt table and typeset a first row with the meta information for our list. The functions for <code>item</code> and <code>model</code> do nothing more than print the argument of the connected elements as table rows and as the first table column. Things get a bit more interesting for the <code>price</code> function: this is where we use the power of Lua to do some easy calculations and convert the Euros to other currencies. First, we extract the content of the <code><price></code> element. We need to tell Lua that this content is not a string, but a number, hence the use of the <code>tonumber</code> function. Within a ConTeXt environment, we would use <code>\xmltext{#1}{./}</code>. The Lua equivalent is <code>xml.text(t, "./")</code>. Now that we have this content as a number, we can perform all kinds of arithmetic operations on it. Likewise, if it were a string, we could use Lua string manipulations on it – that's the good thing about using Lua, you have the full power of the language at your disposal. And finally, we typeset the results of our arithmetic operations in table cells.