
The GAP 4 package CrystCat provides a catalog of crystallographic 
groups of dimensions 2, 3, and 4 which covers most of the data contained 
in the book "Crystallographic groups of four-dimensional space" by 
H. Brown, R. B\"ulow, J. Neub\"user, H. Wondratschek, and H. Zassenhaus 
(John Wiley, New York, 1978). This catalog was previously available in 
the library of GAP 3. The present version for GAP 4 has been moved into 
a separate package, because it requires the package Cryst, which is
loaded automatically. The benefit of this is that space groups 
extracted from the catalog now have the rich set of methods provided 
by Cryst at their disposal, and are no longer dumb lists of generators. 
Moreover, space groups are now fully supported in both the representation
acting from the left and the representation acting from the right.

CrystCat is distributed together with GAP, and does not require any
installation. It is loaded with the GAP command

gap> LoadPackage( "crystcat" ); 

The catalog was brought into GAP format, and ported later to GAP 4 by 

    Volkmar Felsch, Lehrstuhl D f\"ur Mathematik, RWTH Aachen,
    volkmar.felsch@math.rwth-aachen.de

The integration with Cryst is by

    Franz G\"ahler, Fakult\"at f\"ur Mathematik,
    Universit\"at Bielefeld, gaehler@math.uni-bielefeld.de

Please sent bug reports to any of these email addresses.
