ModularGroup.m is a Mathematica package which has been developed in the course of the diploma thesis Computer Algebra and Analysis: Complex Variables Visualized, carried out at the Research Institute for Symbolic Computation (RISC) of the Johannes Kepler University Linz by Thomas Ponweiser under supervision of Univ.-Prof. Dr. Peter Paule.
Version 0.1 of this Mathematica package has been released here.
In this repository, extensions and improvements of ModularGroup.m may get available in the near future.