hatex-guide-1.3.1.2: src/class.htxg

#The LaTeXC class#

\hatex has two different interfaces. One uses blocks as \{Monoid\} elements and the other
as \{Monad\} actions. If we want to keep both interfaces we have two choices: to duplicate
function definitions\f
This was the approach taken in \hatex 3 until the version 3.3, where the \{LaTeXC\} class was included.
\f
or to have a typeclass which unifies both interfaces. Since having duplicate definitions is hard work
and can raise many problems\f
In fact, we had a problem with \hatex-meta, the program that automatically generated the duplicated functions.
The problem was described in the following blog post: <http://deltadiaz.blogspot.com.es/2012/04/hatex-trees-and-problems.html>.
\f, we took the second alternative and defined the \{LaTeXC\} typeclass. Both \{LaTeX\} and \{LaTeXT m a\} are
instances of \{LaTeXC\} (the second one is a little tricky), so every function in \hatex is defined using this
typeclass. This way, we can have both interfaces with a single import, without being worried about maintaining
duplicated code. The cost for this is that we must have class constraints in our type signatures. However, these constraints are only
required in the package. At the user level, you choose your interface and write type signatures correspondingly.