[GAP Forum] Public release of GAP 4.5

[Stephen Linton]

Dear GAP Forum,

After several beta-releases, we are happy to announce the public release of
GAP 4.5.

The new release of GAP, version 4.5.4, is available for download from the
GAP website:

	http://www.gap-system.org

The GAP distribution now has the form of a single archive which contains
the core GAP system and all currently redistributed GAP packages. There are
no optional archives to download. All you need is to get one of the
.tar.gz, .tar.bz2 or .zip archives for UNIX, Linux and Mac OS X, or the
-win.zip archive for Windows. The latter includes not only Windows binaries
for GAP but also for several packages, namely Browse, cvec, EDIM, Grape, IO
and orb which are now fully functional under Windows.

There are many new features introduced in this release. The best way to
learn about them is to read Chapter "Changes between GAP 4.4 and GAP 4.5" 
from the new changes manual. You may access this Chapter by entering 
'?Changes between GAP 4.4 and GAP 4.5' in GAP or browse it online here:

	http://www.gap-system.org/Manuals/doc/changes/chap2.html

The process of installing the core GAP system from the source has not
changed. You call './configure' and then 'make'. However, please note that
to obtain a fully functional GAP installation you not only need to compile
the core system, but also some of its packages. Some of the changes to GAP
have altered what is going on "inside" the installation process: by default
GAP will be using the GMP library for faster large integer arithmetic;
furthermore, if the readline library is detected on your system at compile
time, it will be used for command line editing.

To avoid the need to manage the compilation of GAP and packages yourself, 
you might want to consider one of the alternative installation methods 
below which achieve this for you automatically:

* a Linux binary distribution via remote synchronisation with a reference
 installation which includes all packages and some optimisations.

* BOB - a tool to download and build GAP and its packages from source for
 Linux and Mac OSX. You only download BOB who does all the rest for you. 
 You need a C-compiler and some libraries installed on your system but 
 BOB will tell you exactly what, if anything, is missing.

* a GAP Installer for Windows with the same content as the -win.zip 
 archive. It provides a standard installation procedure that will guide 
 you through all steps of the installation process, and will adjust all 
 paths if GAP will be installed in a non-default location.

These alternatives are individually maintained by some of the GAP
developers. They were all tested with GAP 4.5.4 as part of the release
preparation, and we expect them to be regularly updated in the future. 
They are linked at:

	http://www.gap-system.org/Download/#alternatives

Because we no longer plan to supply upgrade archives, or archives of the 
GAP core system without  packages, and because we hope to release upgrades 
of GAP 4.5 much more frequently, we now recommend all users to keep custom 
packages, i.e. packages that we do not distribute and development versions 
of packages that we do distribute, separately from their GAP installation, 
in a private GAP root directory. In GAP 4.5, one such private root is now 
searched by default (you can use command-line options to include others). 
This will enable you to upgrade your GAP installation very simply without 
losing any custom packages or personal settings. The name of this directory 
depends on your operating system and can be found in the GAP variable
GAPInfo.UserGapRoot. The .gaprc file is now replaced by two files located 
in this directory, gap.ini and gaprc (see '?The gap.ini and gaprc files' 
and also '?The former .gaprc file' if you  have used a .gaprc file with 
GAP 4.4). 

An easy way to make use of the new setup is to use the command
 WriteGapIniFile(); 
within a GAP session. It will tell you the file it has generated.
You can then edit this generated gap.ini file for user customisation 
(preferred packages, colored prompt, external pager, etc.).

Finally, please note these potentially incompatible changes:

* The zero polynomial now has degree -infinity, 
see ?DegreeOfLaurentPolynomial.

* Multiple unary + or - signs are no longer allowed, to avoid confusion 
with increment/decrement operators from other programming languages.

* Due to changes to improve the performance of records with large number of 
components, the ordering of record components in `View'ed records has 
changed.

* Due to improvements for vectors over finite fields, certain objects have 
more limitations on changing their base field. For example, one can not
create a compressed matrix over GF(2) and then assign an element of GF(4) 
to one of its entries.

We encourage all users to upgrade to GAP 4.5.  If you need any help or 
would like to report any problems, please do not hesitate to contact us 
at support at gap-system.org.

Wishing you fun and success using GAP,

The GAP Group