The GAP 4 package Cryst, previously known as CrystGap, is the 
successor of the CrystGap package for GAP 3. During the porting 
process to GAP 4, large parts of the code have been rewritten, and 
the functionality has been extended considerably. Cryst provides a 
rich set of methods to compute with affine crystallographic groups, 
in particular space groups. In constrast to the GAP 3 version, 
affine crystallographic groups are now fully supported both in the 
representation acting from the right and in the representation 
acting from the left. The latter representation is the one preferred 
by crystallographers. There are also functions to determine 
representatives of all space group types of a given dimension. 

Cryst is implemented in the GAP 4 language, and runs on any
system supporting GAP 4. It requires at least GAP version 4.4. 
It is recommended, however, to use the most recent version of GAP. 
Certain commands may need other GAP packages such as CARAT or XGAP. 
Both CARAT and XGAP are available only under Unix. CARAT may be 
required by functions that need to know normalizers or conjugators 
of finite unimodular groups in GL(n,Z) (see the section on normalizers 
of the Cryst manual). The function WyckoffGraph needs the package XGAP.

To install Cryst, just unpack the archive in the pkg subdirectory
of your GAP installation (or in the pkg subdirectory of any other
GAP root directory). Cryst is then loaded with the GAP command

gap> LoadPackage( "cryst" ); 

Cryst has been developed by

Bettina Eick,
Institut Computational Mathematics,
Fachbereich Mathematik und Informatik,
Technische Universit\"at Braunschweig,
Pockelsstr. 14, D-38106 Braunschweig, Germany
e-mail: beick@tu-bs.de

Franz G\"ahler,
Fakult\"at f\"ur Mathematik, Universit\"at Bielefeld,
Postfach 10 01 31, D-33501 Bielefeld, Germany 
e-mail: gaehler@math.uni-bielefeld.de

Werner Nickel,
Fachbereich Mathematik, AG2,
Technische Universit\"at Darmstadt,
Schlossgartenstrasse 7, D-64289 Darmstadt, Germany
e-mail: nickel@mathematik.tu-darmstadt.de

Please send bug reports, suggestions and other comments to any of these
e-mail addresses.