A GAP package supporting computations with Weyl modules and simple modules for a given simply-connected, semisimple, algebraic group in positive characteristic. The package computes submodule structure, simple characters, and decomposition numbers. The package also has some (limited) support for Schur algebras and symmetric groups.  Current version is Version 1.1.  

Version 1.1:  GAP-files, User-manual  (bug fix - manual did not change)
Version 1.0:  GAP-files, User-manual
Version 0.5:  GAP-files, User-manual

To try the software, download the GAP-files (a zip archive) and unpack it somewhere. It should unpack into three files (weyl.g, weylmod.gd, and weylmod.gi).  From the same folder where you unpacked those files, initiate GAP by typing:

    $ gap weyl.g

in a command shell. This will load the package into GAP's memory, and you should now be able to test the commands. Alternatively, you can start a GAP session as usual and then load the package by typing the GAP command:

    gap> Read( "weyl.g" );

if you initiated the GAP session from the same folder containing the file "weyl.g".  If not, you will need to tell GAP what path to use or specify a pathname on the Read command (and perhaps edit the file "weyl.g" to contain correct pathnames as well).

Please report any problems.