Aclib -- A Library of 3- and 4-Dimensional Almost Crystallographic Groups ========================================================================= by Karel Dekimpe and Bettina Eick Introduction ------------ The package `aclib' contains the almost crystallographic groups as classified by K. Dekimpe in the Springer Lecture Notes, Vol. 1639: "Almost Bieberbach Groups: Affine and Polynomial Structures". The groups are available as rational matrix groups. Further, all the groups in the library are polycyclic. If the `Polycyclic' package for computations with infinite polycyclic groups is installed, then also polycyclic presentations for the almost crystallographic groups are available and can be used for computations with these groups. Contents -------- With this version you should have obtained the following files and directories: doc the manual gap the GAP code init.g the file that initializes this package read.g The file that reads in the package The package is written in the GAP language and it can be used with GAP 4.2 and the GAP development version. Installation ------------ There are two ways of installing this package. See also the GAP 4 manual about the installation of share packages. First, download the archive with the package from the web-site http://www.mathematik.uni-kassel.de/~eick/so.html to your computer. Unpack the archive. This creates a directory `aclib'. Similarly, you can download and unpack the package `Polycyclic' which creates a directory `polycyclic'. If you have write access to the GAP root directory on your system, then copy `aclib' (and `polycyclic') into the subdirectory `pkg' of the GAP root directory. If you do not have write access to the GAP root directory, you can also install `aclib' (and `polycyclic') anywhere in your home directory. For this create a directory 'pkg' and move `aclib' (and `polycyclic') into this directory. Let's say the full name is '/home/itsme/compalg/pkg'. Now GAP needs to be told that is should scan that directory for share packages. This is achieved by calling gap with the option -l: gap4 -l '/home/gap/4.0/;/home/itsme/compalg/' The option -l takes a list of directory names separated by semicolons. In the example, the first directory is the directory where GAP is installed on your system and the second one is the one where your `pkg' directory is. If you do not know where GAP is installed on your system, here is a way of finding out: Start GAP and type in GAP_ROOT_PATHS; gap> GAP_ROOT_PATHS; [ "/home/gap/4.0/" ] gap> You will get a list of strings. Use these strings as argument for the -l option with your GAP directory appended to the list. Once you have successfully installed `Aclib', start GAP (possibly using the option -l) and type in gap> RequirePackage( "aclib" ); true; gap> If `Polycyclic' is installed as well, then `Aclib' will load `Polycyclic' automatically.