HTheta is a Haskell library designed for studying the combinatorics of the
cell category Theta of Joyal. It was written as part of a research project
(joint with Georges Maltsiniotis) whose purpose was to define orientals for
the objects of Theta (similar to the orientals of Street for the simplex
category Delta). The program showed that this is impossible for objects of
Theta of dimension 4 on. As a workaround, we introduced a subcategory Xi of
Theta which is also implemented in HTheta.

HTheta can be used interactively with ghci. For instance, the following ghci
session computes the number of subojects in Theta of the object indexing the
exchange law:

ghci> :l Theta/Monos
Ok, modules loaded: Theta, Theta.Monos, ExtList, Theta.Objects, Delta.
ghci> :m + Theta
ghci> length $ subObjs $ wreath2 (delta 2) (delta 2)
169

(This number shows why a computer program might help!)

The tarball contains five short standalone programs showing how the library
can be used (all these programs where written for our own research and are
not ad hoc examples).

There is no documentation for the library and almost no comments in the
source code. If you are interested in doing some computations related to
Theta, feel free to contact me.

Dimitri Ara (d.ara@math.ru.nl)
