# Description

This is a proposal for a new feature I would like to see (and implement) in HaTeX for its next version.
It consists in a new type class, with tentative name `Texy` (*tex-like* or *tex-ify* shortened). Other
names are to be proposed, if any other better is found. The class would contain every type whose values
can be pretty-printed in LaTeX form. Therefore, the definition of the class would be as follows:

class Texy t where texy :: LaTeXC l => t -> l

We can also make `Texy` a subclass of `Render`, so we can have a default implementation using `rendertex`.

class Render t => Texy t where texy :: LaTeXC l => t -> l -- Default implementation texy = rendertex

But I am not sure if this is suitable. The purpose of `Texy` is to build, from Haskell values, more complex
LaTeX expressions than just rendering to `Text`, which, in the other hand, it is no more than a `Show` instance
after all. It may work with numbers but not with more complex values like fractions or matrices.

# Applications

A first application could be `Rational` pretty-printing as fractions using the `frac` function. However, we
also have a problem here: the constructor `%` for rational numbers is already in use in our library. Perhaps
we should rename the comment operator to `%:`? I have not seen an extensive use of this operator yet.

We would also be able to create LaTeX values for tuples, resizing the parenthesis in the tuple appropriately
using `autoParens`.

Another application, perhaps more sofisticated, is pretty-printing matrices. Since the elements of the matrix
would be a `Texy` instance as well, we can use `texy` to pretty-print to LaTeX matrices which may contain
fractions or any other user-supplied value. This is an interface much more flexible than the current one (using
a plain `Render` instance for the elements).

When rendering trees (see `Text.LaTeX.Packages.Trees.Qtree`), we are already using a `LaTeXC l => (a -> l)`
parameter in order to pretty-print the elements of the tree. This is a more free version of the `Texy`
class, which allow the user to supply different ways to generate LaTeX values from a single type.
However, this is not a point against the current proposal, since this functionality can be kept as it is
and added wherever is needed.

I honestly think this would be a good improvement.