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Programming in LuaTeX (view source)
Revision as of 18:28, 17 November 2009
, 18:28, 17 November 2009→Parsing input without exploding your~head
The lua functions such as <code>context.bTABLE()</code> and <code>context.bTR()</code> are just abbreviations for running <code>context ("\\bTABLE")</code>, <code>context("\\bTR")</code>, etc. See the [http://www.pragma-ade.com/general/manuals/cld-mkiv.pdf ConTeXt lua document] manual for more details about such functions. The rest of the code is a simple nested for-loop that computes the sum of two dice. We do not need to worry about macro expansion at all!
= Parsing input without exploding your~head =
In order to get around the weird rules of macro expansion, writing a parser in TeX involves a lot of macro jugglery and catcode trickery. It is a black art, one of the biggest mysteries of TeX for ordinary users.
As an example, let's consider typesetting chemical molecules in TeX. Normally, molecules should be typeset in text mode rather than math mode. For example, <context>H\low{2}SO\lohi{4}{--}</context>, can be input as <code>H\low{2</code>}SO\lohi{4}{--}}</code>. Typing so much markup can be cumbersome. Ideally, we want a macro such that we type <code>\molecule{H_2SO_4^-}</code>} and the macro translates this into <code>H\low{2</code>}SO\lohi{4}{--}}</code>. Such a macro can be written in TeX as follows.
<texcode>
\newbox\chemlowbox
