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Iterated monodromy groups in GAP

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                             The IMG package

This is the README file for the GAP package "IMG".

This package implements Functionally Recursive and Mealy automata in
GAP. These objects can be manipulated as group elements, and various
specific commands allow their manipulation as automorphisms of infinite
rooted trees. Permutation quotients can also be created and manipulated
as standard GAP groups or semigroups.

This release (1.0) is the first containing all the planned functionality,
though some rough edges will still need to be smoothed. In particular,
the TODO file describes plans for future development, including
computations of presentations for self-similar groups, interval arithmetic
for complex dynamics, etc.

The package is distributed in source form, and does not require anything
else than a running GAP 4.5 or later. For updates, check (tar.gz formats)
and (git)

To use the package, start GAP and type


The "IMG" package banner should appear on the screen.

For details on how to use the IMG package, please consult the documentation.
Though this is usually not necessary, it may be recompiled, after the command
`LoadPackage("IMG")', by invoking


at the GAP prompt. The documentation will then be available in the `doc'
subdirectory (view the file `manual.pdf' via a PDF viewer).

An optional external module (DLL) provides floating-point functions used
by the "iterated monodromy groups" part of IMG. Its presence or absence
does not affect the remainder of IMG. To compile it, first make sure that
your system has C and JAVA compilers. You will need some external libraries,
in particular levmar and libdogleg. To install them:

* on Linux, use a package-manager such as 'apt-get', 'rpm' if possible. On
  debian/ubuntu systems, you will need libsuitesparse-dev.
* on UNIX systems, install the libraries:
  The dogleg library may be found at
  The levmar library may be found at

* on Mac OSX, use 'homebrew' (, and install the formulas by invoking
  % brew install 
  % brew install

* on Windows, use an appropriate UNIX-like environment such as cygwin, and follow the UNIX

In all cases, then run

'./configure && make' in IMG's root directory.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or any
later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program, in the file COPYING.  If not, see

  Laurent Bartholdi, Göttingen, 16 November 2012
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