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CLD ('''ConTeXt Lua Documents''' (CLD) are way to access TeX from inside Lua scripts; they provide means to typeset documents using little to no TeX code at all.
== Basic reading ==* [http://www.pragma-ade.comnl/general/manuals/cld-mkiv.pdf The CLD manual] by Hans Hagen.* [[source:mult{{src|cldf-cldini.lua| The source code}}: the entry point for the '''cldf-*''' files that contain the CLD implementation.]]
== An Example ==
With CLDs As <em>CLD</em> this will require more verbosity because nesting -- in the present example a <code>framed</code> inside a <code>placefigure</code> -- has to be expressed through functions.
→Setting up Header Texts
This makes them especially helpful for automated content generation and scripting.
Internally, the Lua commands are mapped onto their ConTeXt and TeX counterparts.
If you ever dreamed of proper typesetting without backslashes galore, here is where to start at.
Writing CLDs is straightforward although there are some pitfalls.
Suppose we want to typeset the following minimal example:
</context>
Optional and key-value style arguments are expressed as arrays and dictionaries respectively, which is a transparent representation of their ConTeXt ancestors.
Mandatory (grouped) arguments are given either as strings or as functions.
== Nesting 1: Functions ==The following example shows two ways of rewriting the above TeX code: the first one closely resembles its structure while the second calls the function <code>test</code> from inside the <code>placefigure</code> macro -- NB: it is compulsory to call a declared function by means of another function, otherwise ConTeXt can't process it.(Works with latest ConTeXt beta as of 2010-03-10.)
<pre>
context.placefigure(
</pre>
== Nesting 2: Delayed ==
An alternative to the function encapsulation is provided by
the <tt>context.delayed.f()</tt> method.
This way execution of the <tt>\input</tt>
command is prevented until <tt>\placefigure</tt> is passed to TeX,
the obvious advantage being that the source code follows the
original TeX code and that it eliminates the need to create
a separate function.
<pre>
context.placefigure(
"none",
function()
context.framed( {
frame="on",
align="middle"
},
context.delayed.input("knuth")
)
end
)
</pre>
= Setting up Header Texts =
As already shown in the section about Nesting 1: Functions also context.setupheadertexts needs to be called with functions. On top of this we need to know, that once context.setupheadertexts is executed it is not frozen. This makes it necessary, that we need to add "return true" inside each used function() call. This makes sure that the called function stays around until the run is finished.
A complete setup of header texts in a double-sided ConTeXt Lua Document could look then like this
<pre>
context.setupheadertexts(
{function()
context.getmarking({"chapter"})
return true
end
},
{function()
context.pagenumber()
return true
end
},
{function()
context.getmarking({"section"})
return true
end
},
{function()
context.pagenumber()
return true
end
})
</pre>
[[Category:Programming and Databases]]
