changes45.xml

<Chapter Label="ChangesGAP44toGAP45"> 
<Heading>Changes between &GAP; 4.4 and &GAP; 4.5</Heading>

This chapter lists most important changes between &GAP; 4.4.12 and the
first public release of &GAP; 4.5. It also contains information about
subsequent update releases for &GAP; 4.5.
It is not meant to serve as a complete account on all improvements; 
instead, it should be viewed as an introduction to &GAP; 4.5,
accompanying its release announcement.

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> 
<Section Label="Changes in the core GAP45 system"> 
<Heading>Changes in the core &GAP; system introduced in &GAP; 4.5</Heading>

In this section we list most important new features and bugfixes in the core 
system introduced in &GAP; 4.5. For the list of changes in the interface 
between the core system and packages as well as for an overview of new and 
updated packages, see Section <Ref Sect="Packages in GAP45"/>.

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> 
<Subsection Label="Improved mathematical functionality"> 
<Heading>Improved functionality</Heading>
<!-- TODO: Remove anything non-mathematical to another section -->

Performance improvements:

<List>
<Item>
<Index><Package>GMP support</Package></Index>
The &GAP; kernel now uses <Package>GMP</Package> (GNU multiple precision 
arithmetic library, <URL>http://gmplib.org/</URL>) for faster large integer 
arithmetic.
</Item>
<Item>
Improved performance for records with large number of components.
</Item>
<Item>
Speedup of hash tables implementation at the &GAP; library level.
</Item>
<Item>
<Ref Oper="MemoryUsage" BookName="ref"/> is now much 
more efficient, in particular for large objects. 
</Item>
<Item>
Speedups in the computation of low index subgroups, Tietze transformations,
calculating high powers of matrices over finite fields, 
<Ref Func="Factorial" BookName="ref"/>, etc.
</Item>
</List>

New and improved kernel functionality:

<List>
<Item>
By default, the &GAP; kernel compiles with the <Package>GMP</Package> and 
<Package>readline</Package> libraries. The <Package>GMP</Package> library 
is supplied with &GAP; and we recommend that you use the version we
supply. There are some problems with some other versions.
It is also possible to compile the &GAP; kernel with the system 
<Package>GMP</Package> if your system has it. 
The <Package>readline</Package> library must be 
installed on your system in advance to be used with &GAP;.
</Item>
<Item>
<Index>Floats</Index>
Floating point literals are now supported in the &GAP; language, so that,
floating point numbers can be entered in &GAP; expressions in a natural
way. Support for floats is now properly 
documented, see <Ref Chap="Floats" BookName="ref"/>. &GAP; has an interface 
using which packages may add new floating point implementations and
integrate them with the parser. In particular, we expect that there will soon
be a package that implements arbitrary precision floating point arithmetic.
</Item>
<Item>
The Mersenne twister random number generator has been made 
independent of endianness, so that 
random seeds can now be transferred between architectures. See 
<Ref Sect="GlobalMersenneTwister" BookName="ref"/> for details.
</Item>
<Item>
Defaults for <C>-m</C> and <C>-o</C> options have been increased.
Changes have been made to the way that &GAP; obtains memory from
the Operating System, to make &GAP; more compatible with C libraries. 
A new <C>-s</C> option has been introduced to control or turn off the
new behaviour, see <Ref Sect="Command Line Options" BookName="ref"/>.
</Item>
<Item>
The filename and lines from which a function was read can now be
recovered using <Ref Func="FilenameFunc" BookName="ref"/>,
<Ref Func="StartlineFunc" BookName="ref"/> and 
<Ref Func="EndlineFunc" BookName="ref"/>. 
This allows you, for example, to implement a
function such as <Ref Func="PageSource" BookName="ref"/> to show the file 
containing the source code of a function or a method in a pager,
see <Ref Func="Pager" BookName="ref"/>.
</Item>
<Item>
<Ref Oper="CallFuncList" BookName="ref"/> was made into an operation 
so that it can be used to define behaviour of a non-function when 
called as a function.
</Item>
<Item>
Improvements to the cyclotomic number arithmetic for fields with large conductors.
</Item>
<Item>
Better and more flexible viewing of some large objects.
</Item>
<Item>
Opportunity to interrupt some long kernel computations, 
e.g. multiplication of compressed matrices, intercepting
<C>Ctrl-C</C> in designated places in the kernel code
by means of a special kernel function for that purpose.
</Item>
<Item>
<C>ELM_LIST</C> now allows you to install methods where the second argument is 
NOT a positive integer.
</Item>
<Item>
Kernel function <Ref Func="DirectoryContents" BookName="ref"/> to get 
the list of names of files and subdirectories in a directory.
</Item>
<Item>
Kernel functions for Kronecker product of compressed matrices,
see <Ref Func="KroneckerProduct" BookName="ref"/>.
</Item>
</List>

New and improved library functionality:

<Index>Data libraries</Index>
<List>
<Item>
Extensions of data libraries: 
<List>
<Item>
Functions and iterators are now available to create and enumerate 
simple groups by their order up to isomorphism: 
<Ref Func="SimpleGroup" BookName="ref"/>,
<Ref Func="SmallSimpleGroup" BookName="ref"/>,
<Ref Func="SimpleGroupsIterator" BookName="ref"/> and
<Ref Func="AllSmallNonabelianSimpleGroups" BookName="ref"/>.
</Item>
<Item>
See also packages <Package>CTblLib</Package>, 
<Package>IRREDSOL</Package> and <Package>Smallsemi</Package> listed 
in Section <Ref Sect="New and updated packages since GAP 4.4.12"/>.
</Item>
</List>
</Item>
<Item>
Many more methods are now available for the built-in floating point numbers,
see <Ref Chap="Floats" BookName="ref"/>.
</Item>
<Item>
The bound for the proper primality test in
<Ref Func="IsPrimeInt" BookName="ref"/> 
increased up to <M>10^{18}</M>.
</Item>
<Item>
Improved code for determining transversal and double coset representatives in large groups.
</Item>
<Item>
Improvements in <Ref Oper="Normalizer" BookName="ref"/> for <M>S_n</M>.
</Item>
<Item>
Smith normal form of a matrix may be computed over arbitrary euclidean rings,
see <Ref Oper="NormalFormIntMat" BookName="ref"/>.
</Item>
<Item>
Improved algorithms to determine the subgroup lattice of a group,
as well as the function <Ref Func="DotFileLatticeSubgroups" BookName="ref"/>
to save the lattice structure in <F>.dot</F> file to view it e.g. with
<Package>GraphViz</Package>.
</Item>
<Item>
Special teaching mode which simplifies some output and provides 
more basic functionality, see <Ref Sect="Teaching Mode" BookName="ref"/>.
</Item>
<Item>
Functionality specific for use in undergraduate abstract algebra
courses, e.g. checksums (<Ref Sect="Check Digits" BookName="ref"/>);
string/integer list conversion; rings of small orders; the function
<Ref Func="SetNameObject" BookName="ref"/> to set display names for
objects for more informative examples, e.g. constructing groups 
from <Q>named</Q> objects, such as, for example, <C>R90</C> for a 
90-degree rotation).
<!-- See section 3.3 of "Abstract Algebra in GAP" booklet by AH:
     http://www.math.colostate.edu/~hulpke/CGT/howtogap.pdf -->
</Item>
<Item>
Functions <Ref Func="DirectoryDesktop" BookName="ref"/> and
<Ref Func="DirectoryHome" BookName="ref"/> which provide uniform 
access to default directories under Windows, Mac OS X and Unix.
</Item>
<Item>
Improved methods for hashing when computing orbits.
</Item>
<Item>
Functionality to call external binaries under Windows.
</Item>
<Item>
Symplectic groups over residue class rings,
see <Ref Func="SymplecticGroup" BookName="ref"/>.
</Item>
<Item>
Basic version of the simplex algorithm for matrices.
</Item>
<Item>
New functions, operations and attributes: 
<Ref Attr="PrimeDivisors" BookName="ref"/>, 
<Ref Oper="Shuffle" BookName="ref"/> for lists, 
<Ref Func="IteratorOfPartitions" BookName="ref"/>,
<Ref Func="IteratorOfCombinations" BookName="ref"/>,
<Ref Func="EnumeratorOfCombinations" BookName="ref"/>
and others.
</Item>
<Item>
The behaviour of <Ref Func="Info" BookName="ref"/> statements can now be 
configured per info class, this applies to the way the arguments are 
printed and to the output stream, see <Ref Sect="Info Functions" BookName="ref"/>.
</Item>
<Item>
New function <Ref Func="Test" BookName="ref"/>  which is a more flexible and
informative substitute of <C>ReadTest</C> operation.
</Item>
<Item>
<C>ConnectGroupAndCharacterTable</C> is replaced by more robust 
function <Ref Func="CharacterTableWithStoredGroup" BookName="ref"/>.
</Item>
</List>

Many problems in &GAP; have have been fixed, among them the following:

<List>
<Item>
Polynomial factorisation over rationals could miss factors of degree 
greater than <M>deg(f)/2</M> if they have very small coefficients, while 
the cofactor has large coefficients.
</Item>
<Item>
<Ref Oper="IntermediateSubgroups" BookName="ref"/> called on a group and
a normal subgroup did not properly calculate maximal inclusion relationships.
</Item>
<Item>
<Ref Attr="CentreOfCharacter" BookName="ref"/> and 
<Ref Attr="ClassPositionsOfCentre" BookName="ref" Label="for a character"/>
called for a group character could return a perhaps too large result.
</Item>
<Item>
<Ref Attr="Trace" BookName="ref"/> called for an element of a finite field 
that was created with <Ref Oper="AlgebraicExtension" BookName="ref"/>
ran into an error.
</Item>
<Item>
<Ref Func="IrreducibleRepresentationsDixon" BookName="ref"/> did not accept 
a list with one character as a second argument.
</Item>
<Item>
Composing a homomorphism from a permutation group to a finitely presented
group with another homomorphism could give wrong results.
</Item>
<Item>
For certain arguments, the function <Ref Func="EU" BookName="ref"/> 
returned wrong results.
</Item>
<Item>
In the table of marks of cyclic groups, 
<Ref Attr="NormalizersTom" BookName="ref"/> value was wrong.
</Item>
<Item>
The function <Ref Func="PermChars" BookName="ref"/> returned a perhaps 
wrong result when the second argument was a positive integer (not a record)
and the trivial character of the character table given as the first argument
was not the first in the list of irreducibles.
</Item>
<Item>
&GAP; crashed when the intersection of ranges became empty.
</Item>
<Item>
<C>IsPSL</C>, and in turn <Ref Func="StructureDescription" BookName="ref"/>,
erroneously recognised non-PSL groups of the right order as PSL.
</Item>
<Item>
The semidirect product method for pcgs computable groups sometimes tried to use 
finite presentations which were not polycyclic. This usually happened when the
groups were not pc groups, and there was a very low risk of getting a wrong result.
</Item>
<Item>
The membership test for a group of finite field elements ran into an error 
if the zero element of the field was given as the first argument.
</Item>
<Item>
Constant polynomials were not recognised as univariate in any variable.
</Item>
<Item>
The kernel recursion depth counter was not reset properly when
running into many break loops.
</Item>
<Item>
&GAP; did not behave well when printing of a (large) object was 
interrupted with <C>Ctrl-C</C>. Now the object is no longer corrupted 
and the indentation level is reset.
</Item>
</List>

Potentially incompatible changes:

<List>
<Item>
The zero polynomial now has degree <C>-infinity</C>,
see <Ref Attr="DegreeOfLaurentPolynomial" BookName="ref"/>.
</Item>
<Item>
Multiple unary <C>+</C> or <C>-</C> signs are no longer allowed 
(to avoid confusion with increment/decrement operators from other 
programming languages).
</Item>
<Item>
Due to changes to improve the performance of records with large number of 
components, the ordering of record components in <C>View</C>'ed records 
has changed.
</Item>
<Item>
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 <M>GF(2)</M> and then assign an element 
of <M>GF(4)</M> to one of its entries.
</Item>
</List>

<Index>Completion files (withdrawn)</Index>
<Index>&GAP;&nbsp;3 compatibility mode (withdrawn)</Index>
No longer supported:
<List>
<Item>
Completion files mechanism.
</Item>
<Item>
&GAP; 3 compatibility mode.
</Item>
</List>

<Index>&GAP; compiler (no longer recommended)</Index>
In addition, we no longer recommend using the &GAP; compiler <F>gac</F> to 
compile &GAP; code to <Package>C</Package>, and may withdraw it in future 
releases. Compiling &GAP; code only ever gave a substantial speedup for 
rather specific types of calculation, and much more benefit can usually be 
achieved quite easily by writing a small number of key functions in 
<Package>C</Package> and loading them into the kernel as described in
<Ref Func="LoadDynamicModule" BookName="ref"/>. The <F>gac</F> script will 
remain available as a convenient way of compiling such kernel modules from 
<Package>C</Package>.
<P/>

Also, the following functions and operations were made obsolete:
<C>AffineOperation</C>,
<C>AffineOperationLayer</C>,
<C>FactorCosetOperation</C>,
<C>DisplayRevision</C>,
<C>ProductPol</C>,
<C>TeXObj</C>,
<C>LaTeXObj</C>.

</Subsection>


<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> 
<Subsection Label="GAP45 Distribution"> 
<Heading>Changes in distribution formats</Heading>

<Index Key="tools"><F>tools</F> archive</Index>
The &GAP; 4.5 source distribution has the form of a 
single archive containing the core system and the most recent <Q>stable</Q> 
versions of all currently redistributed packages. There are no optional
archives to download: the <Package>TomLib</Package> package now contains all 
its tables of marks in one archive; we do not provide separate versions of 
manuals for Internet Explorer, and the former <F>tools</F> archive is now
included as an archive in the <F>etc</F> directory.
To unpack and install the archive, user the script
<F>etc/install-tools.sh</F>.
<P/>

<Index>Bugfixes and packages archives (withdrawn)</Index>
We no longer distribute separate bugfix archives when the core &GAP;
system changes, or updated packages archives when a redistributed
package is updated. Instead, the single &GAP; source distribution 
archive will be labelled by the version of
the core &GAP; system and also by a timestamp. This archive contains
the core system and the 
stable versions of the relevant packages on that date. 
To upgrade, you simply
replace the whole directory containing
 the &GAP; installation, and rebuild binaries 
for the &GAP; kernel and packages. For new versions of packages, we will also
continue to redistribute individual package archives so it will be
possible to update a single package without changing the rest of the 
&GAP; installation.
<P/>

Furthermore, by default &GAP; will now automatically read a user-specific 
&GAP; root directory (unless &GAP; is called with the <C>-r</C> option). 
All user settings can be made in that directory, so there will be no risk 
of them being lost during an update (see Section 
<Ref Sect="GAP45 User interface"/> below for more details). Private
packages can also be installed in this directory for the same reason.
<P/> 

There are some changes in archive formats used for the distribution: we
continue to provide <F>.tar.gz</F>, <F>.tar.bz2</F> and <F>-win.zip</F>
archives. We have added <F>.zip</F>, and stopped providing <F>.zoo</F> archives.
We no longer provide GAP binaries for Mac OS 9 (Classic) any more. For
installations from source on Mac OS X one may follow the instructions for UNIX.
<P/>

<Index>&GAP; binary distributions</Index>
With the release of &GAP; 4.5, we also encourage more users to take
advantage of the increasingly mature binary distributions which are
now available. These include:

<List>

<Item>
The binary <F>rsync</F> distribution for &GAP; on Linux PCs with i686 
or x86_64 compatible processors provided by Frank Lübeck, see
<URL>http://www.math.rwth-aachen.de/~Frank.Luebeck/gap/rsync</URL>.
</Item>

<Item>
<Package>BOB</Package>, a tool for Linux and Mac OS X to download and build 
&GAP; and its packages from source provided by M. Neunhöffer:
<URL>http://www-groups.mcs.st-and.ac.uk/~neunhoef/Computer/Software/Gap/bob.html</URL>.
</Item>

<Item>
The &GAP; installer for Windows provided by Alexander Konovalov:
<URL>https://www.gap-system.org/ukrgap/wininst/</URL>.
</Item>

</List>
In the near future, we also hope to have a binary distribution for Mac OS X.
<!-- TODO: when ready, add installers for Windows and Mac OS X by AH -->
<P/> 

Internally, we now have infrastructure to support more robust and frequent 
releases, and an improved system to fetch and test new versions of
the increasingly large number of packages. The 
<Package>Example</Package> package documents technical requirements for
packages, many of which are checked automatically by our systems.
This will allow us to check 
the compatibility of packages with the system and with other 
packages more thoroughly before publishing them on the &GAP; website.

</Subsection>

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> 
<Subsection Label="GAP45 User interface"> 
<Heading>Improvements to the user interface</Heading>

<Index><Package>readline</Package> support</Index>
<Index>User interface customisation</Index>
By default, &GAP; now uses the <Package>readline</Package> library for 
command line editing. It provides such advantages as working with 
unicode terminals, nicer handling of long input lines, improved 
TAB-completion and flexible configuration. For further details, see
<Ref Sect="Editing using the readline library" BookName="ref"/>.
<P/>

We have extended facilities for user interface customisation. By default 
&GAP; automatically scans a user specific &GAP; root directory (unless
&GAP; is called with the <C>-r</C> option). The name of this user 
specific directory depends on the operating system and is contained
in <C>GAPInfo.UserGapRoot</C>. This directory can be used to tell &GAP; 
about personal preferences, to load some additional code, to 
install additional packages, or to overwrite some &GAP; files, 
see <Ref Sect="GAP Root Directories" BookName="ref"/>. Instead of
a single <F>.gaprc</F> file we now use more flexible setup based on
two files: <F>gap.ini</F> which is read early in the startup process,
and <F>gaprc</F> which is read after the startup process, but before the 
first input file given on the command line. These files may be located 
in the user specific &GAP; root directory <C>GAPInfo.UserGapRoot</C> 
which by default is the first &GAP; root directory, see 
<Ref Sect="The gap.ini and gaprc files" BookName="ref"/>.
For compatibility, the <F>.gaprc</F> file is still read 
if the directory <C>GAPInfo.UserGapRoot</C> does not exist.
See <Ref Sect="The former .gaprc file" BookName="ref"/> for the 
instructions how to migrate your old setup. 
<P/>

Furthermore, there are functions to deal with user preferences, for example,
to specify how &GAP;'s online help is shown or whether the coloured prompt
should be used. Calls to set user preferences may appear in the user's 
<F>gap.ini</F> file, as explained in 
<Ref Sect="Configuring User preferences" BookName="ref"/>.
<P/> 

In the Windows version, we include a new shell which uses the 
<Package>mintty</Package> terminal in addition to the two 
previously used shells (Windows command line and <Package>RXVT</Package>). 
The <Package>mintty</Package> shell is now recommended. It supports Unicode
encoding and has flexible configurations options. Also, &GAP; under Windows 
now starts in the <F>%HOMEDRIVE%%HOMEPATH%</F> directory, which is the 
user's home directory. Besides this, a larger workspace is now permitted 
without a need to modify the Windows registry.
<P/>

Other changes in the user interface include:
<List>
<Item>
the command line history is now implemented at the &GAP; level, it can be 
stored on quitting a &GAP; session and reread when starting a new session, 
see <Ref Sect="The command line history" BookName="ref"/>.
</Item>
<Item>
<C>SetPrintFormattingStatus("stdout",false);</C> may be used
to switch off the automatic line breaking in terminal output,
see <Ref Func="SetPrintFormattingStatus" BookName="ref"/>.
</Item>
<Item>
&GAP; supports terminals with up to 4096 columns (extendable at compile time).
</Item>
<Item>
Directories in <C>-l</C> command-line option 
can now be specified starting with <C>~/</C>,
see <Ref Sect="Command Line Options" BookName="ref"/>.
</Item>
<Item>
Large integers are now displayed by a short string showing the first
and last few digits, and the threshold to trigger this behaviour 
is user configurable (call <C>UserPreference("MaxBitsIntView")</C> to
see the default value).
</Item>
<Item>
The &GAP; banner has been made more compact and informative.
</Item>
<Item>
<Ref Func="SetHelpViewer" BookName="ref"/> now supports 
the Google Chrome browser.
</Item>
<Item>
Multiple matches in the &GAP; online help are displayed via a function
from the <Package>Browse</Package> package, which is loaded in the 
default configuration. This feature can be replaced by the known pager 
using the command
<Verb>
SetUserPreference( "browse", "SelectHelpMatches", false );
</Verb>
</Item>
</List>

</Subsection>



<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> 
<Subsection Label="GAP45 Documentation"> 
<Heading>Better documentation</Heading>

<Index><Package>MathJax support</Package></Index> The main &GAP;
manuals have been converted to the &GAPDoc; format provided by the
&GAPDoc; package by Frank Lübeck and Max Neunhöffer
(<URL>http://www.math.rwth-aachen.de/~Frank.Luebeck/GAPDoc</URL>).
This documentation format is already used by many packages and is now
recommended for all &GAP; documentation.

<P/>

Besides improvements to the documentation layout in all formats
(text, PDF and HTML), the new &GAP; manuals incorporate a large number
of corrections, clarifications, additions and updated examples.
<P/>

We now provide two HTML versions of the manual, one of them 
with <Package>MathJax</Package> (<URL>http://www.mathjax.org</URL>)
support for better display of mathematical symbols. Also, there are
two PDF versions of the manual - a coloured and a monochrome one.
<P/>

Several separate manuals now became parts of the &GAP; Reference
manual. Thus, now there are three main &GAP; manual books: 
<List>
<Item>
<E>&GAP; Tutorial</E> <Alt Only="HTML">(see <Ref BookName="tut" Label="Preface"/>)</Alt>
<P/>
</Item>
<Item>
<E>&GAP; Reference manual</E> <Alt Only="HTML">(see <Ref BookName="ref" Label="Preface"/>)</Alt>
</Item>
<Item>
<E>&GAP; - Changes from Earlier Versions</E> (this manual)
</Item>
</List>

Note that there is no index file combining these three manuals. Instead
of that, please use the &GAP; help system which will search all of
these and about 100 package manuals.

</Subsection>

</Section>

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> 
<Section Label="Packages in GAP45"> 
<Heading>Packages in &GAP; 4.5</Heading>

Here we list most important changes affecting packages and present new or
essentially changed packages. For the changes in the core &GAP; system, 
see Section <Ref Sect="Changes in the core GAP45 system"/>.

<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> 
<Subsection Label="Interface between the core system and packages">
<Heading>Interface between the core system and packages</Heading>
<Index>Namespaces</Index>

The package loading mechanism has been improved. 
The most important new feature is that all dependencies are evaluated in 
advance and then used to determine the order in which package files are read.
This allows &GAP; to handle cyclic dependencies as well as situations where
package A requires package B to be loaded completely before any file of 
package A is read. To avoid distortions of the order in which packages will
be loaded, package authors are strongly discouraged from calling 
<Ref Func="LoadPackage"  BookName="ref"/> and 
<Ref Func="TestPackageAvailability" BookName="ref"/> in a package code in 
order to determine whether some other package will be loaded before or 
together with the current package - instead, one should use 
<Ref Func="IsPackageMarkedForLoading" BookName="ref"/>.
In addition, there is now
a better error management if package loading fails for packages that use
the new functionality to log package loading messages 
(see <Ref Func="DisplayPackageLoadingLog" BookName="ref"/> 
and the rest of the Chapter <Ref Chap="Using GAP Packages" BookName="ref"/> 
which documents how to <E>use</E> &GAP; packages), and package authors 
are very much encouraged to use these logging facilities.
<P/>

In &GAP; 4.4 certain packages were marked as <E>autoloaded</E> and 
would be loaded, if present, when &GAP; started up. In &GAP; 4.5, this
notion is divided into three. Certain packages are recorded
as <E>needed</E> by the &GAP; system and others as <E>suggested</E>,
in the same way that packages may <E>need</E> or <E>suggest</E> other
packages. If a needed package is not loadable, &GAP; will not
start. Currently only &GAPDoc; is needed. If a suggested package is
loadable, it will be loaded. Typically these are packages which
install better methods for Operations and Objects already present in
&GAP;. Finally, the user preferences mechanism can be used to specify
additional packages that should be loaded if possible. By default this
includes most packages that were autoloaded in &GAP;&nbsp;4.4.12,
see <Ref Func="ShowUserPreferences" BookName="ref"/>.
<P/> 

&GAP; packages may now use local <E>namespaces</E> to avoid name clashes 
for global variables introduced in other packages or in the &GAP;
library, see <Ref Sect="Namespaces for GAP packages" BookName="ref"/>.
<P/>

All guidance on how to <E>develop</E> a &GAP; package has been consolidated 
in the <Package>Example</Package> package which also contains a checklist 
for upgrading a &GAP; package to &GAP;&nbsp;4.5, see 
<Ref Appendix="Guidelines for Writing a GAP Package" BookName="Example"/>.
<P/> 

</Subsection>

<Subsection Label="New and updated packages since GAP 4.4.12"> 
<Heading>New and updated packages since &GAP; 4.4.12</Heading>

At the time of the release of &GAP; 4.4.12 there were 75 packages
redistributed with &GAP; (including the <Package>TomLib</Package>
which was distributed in the core &GAP; archive). The first public release
of &GAP;&nbsp;4.5 contains precisely 99 packages. 
<P/>

The new packages that have been added to the redistribution 
since the release of &GAP; 4.4.12 are: 
<List>
<Item>
<Package>Citrus</Package> package by J.D. Mitchell for computations with 
transformation semigroups and monoids (this package is a replacement of 
the <Package>Monoid</Package> package).
</Item>
<Item>
<Package>cvec</Package> package by M. Neunhöffer, providing an 
implementation of compact vectors over finite fields.
</Item>
<Item>
<Package>fwtree</Package> package by B. Eick and T. Rossmann for 
computing trees related to some pro-<M>p</M>-groups of finite width.
</Item>
<Item>
<Package>GBNP</Package> package by A.M. Cohen and J.W. Knopper, providing 
algorithms for computing Grobner bases of noncommutative polynomials over 
fields with respect to the <Q>total degree first then lexicographical</Q> 
ordering.
</Item>
<Item>
<Package>genss</Package> package by M. Neunhöffer and F. Noeske, 
implementing the randomised Schreier-Sims algorithm to compute a 
stabiliser chain and a base and a strong generating set for arbitrary 
finite groups.
</Item>
<Item>
<Package>HAPprime</Package> package by P. Smith, extending the 
<Package>HAP</Package> package with an implementation of 
memory-efficient algorithms for the calculation of resolutions 
of small prime-power groups.
</Item>
<Item>
<Package>hecke</Package> package by D. Traytel, providing functions 
for calculating decomposition matrices of Hecke algebras of the 
symmetric groups and <M>q</M>-Schur algebras (this package is a port 
of the &GAP;&nbsp;3 package <Package>Specht 2.4</Package> to &GAP;&nbsp;4).
</Item>
<Item>
<Package>Homalg</Package> project by M. Barakat, S. Gutsche,
M. Lange-Hegermann et al., containing the following packages 
for the homological algebra: <Package>homalg</Package>,
<Package>ExamplesForHomalg</Package>, <Package>Gauss</Package>, 
<Package>GaussForHomalg</Package>, <Package>GradedModules</Package>,
<Package>GradedRingForHomalg</Package>, <Package>HomalgToCAS</Package>, 
<Package>IO_ForHomalg</Package>, <Package>LocalizeRingForHomalg</Package>,
<Package>MatricesForHomalg</Package>, <Package>Modules</Package>, 
<Package>RingsForHomalg</Package> and <Package>SCO</Package>
(see <URL>http://homalg.math.rwth-aachen.de/</URL>).
</Item>
<Item>
<Package>MapClass</Package> package by A. James, K. Magaard and
S. Shpectorov to calculate the mapping class group orbits for a 
given finite group.
</Item>
<Item>
<Package>recogbase</Package> package by M. Neunhöffer and A. Seress, 
providing a framework to implement group recognition methods in a 
generic way (suitable, in particular, for permutation groups, matrix 
groups, projective groups and black box groups). 
</Item>
<Item>
<Package>recog</Package> package by M. Neunhöffer, A. Seress, 
N. Ankaralioglu, P. Brooksbank, F. Celler, S. Howe, M. Law,
S. Linton, G. Malle, A. Niemeyer, E. O'Brien and C.M. Roney-Dougal,
extending the <Package>recogbase</Package> package and provides a 
collection of methods for the constructive recognition of groups 
(mostly intended for permutation groups, matrix groups and projective 
groups).
</Item>
<Item>
<Package>SCSCP</Package> package by A. Konovalov and S. Linton, 
implementing the Symbolic Computation Software Composability Protocol 
(<Package>SCSCP</Package>, see 
<URL>http://www.symbolic-computation.org/scscp</URL>) for &GAP;,
which provides interfaces to link a &GAP; instance with another copy
of &GAP; or other <Package>SCSCP</Package>-compliant system running 
locally or remotely.
</Item>
<Item>
<Package>simpcomp</Package> package by F. Effenberger and J. Spreer
for working with simplicial complexes.
</Item>
<Item>
<Package>Smallsemi</Package> package by A. Distler and J.D. Mitchell, 
containing the data library of all semigroups with at most 8 elements 
as well as various information about them.
</Item>
<Item>
<Package>SymbCompCC</Package> package by D. Feichtenschlager for 
computations with parametrised presentations for finite <M>p</M>-groups 
of fixed coclass.
</Item>
</List>

Furthermore, some packages have been upgraded substantially 
since the &GAP;&nbsp;4.4.12 release:

<List>
<Item>
<Package>Alnuth</Package> package by B. Assmann, A. Distler and B. Eick
uses an interface to PARI/GP system instead of the interface to KANT
(thanks to B. Allombert for the GP code for the new interface and help 
with the transition) and now also works under Windows.
</Item>
<Item>
<Package>CTblLib</Package> package (the &GAP; Character Table Library)
by T. Breuer has been extended by many new character tables, a few bugs 
have been fixed, and new features have been added, for example concerning 
the relation to &GAP;'s group libraries, better search facilities, and 
interactive overviews. For details, see the package manual.
</Item>
<Item>
<Package>DESIGN</Package> package by L.H. Soicher:
<List>
<Item>
The functions <C>PointBlockIncidenceMatrix</C>, <C>ConcurrenceMatrix</C>, 
and <C>InformationMatrix</C> compute matrices associated with block designs.
</Item>
<Item>
The function <C>BlockDesignEfficiency</C> computes certain statistical
efficiency measures of a <M>1-(v,k,r)</M> design, using exact algebraic 
computation.
</Item>
</List>
</Item>
 
<Item>
<Package>Example</Package> package by W. Nickel, G. Gamble and A. Konovalov
has a more detailed and up-to-date guidance on developing a &GAP; package,
see <Ref Appendix="Guidelines for Writing a GAP Package" BookName="Example"/>.
</Item>

<Item>
<Package>FR</Package> package by L. Bartholdi now uses floating-point 
numbers to compute approximations of rational maps given by their 
group-theoretical description.
</Item>

<Item>
The <Package>GAPDoc</Package> package by F. Lübeck and M. Neunhöffer
provides various improvements, for example:
<List>
<Item>
The layout of the text version of the manuals can be configured quite
freely, several standard <Q>themes</Q> are provided. The display is now 
adjusted to the current screen width.
</Item>
<Item>
Some details of the  layout of the HTML version of the manuals can now 
be configured by the user. All manuals are available with and without
MathJax support for display of mathematical formulae.
</Item>
<Item>
The text and HTML versions of manuals make more use of unicode 
characters (but the text version is also still reasonably good
on terminals with latin1 or ASCII encoding).
</Item>
<Item>
The PDF version of the manuals uses better fonts.
</Item>
<Item>
Of course, there are various improvements for authors of manuals as 
well, for example new functions 
<Ref Func="ExtractExamples" BookName="gapdoc"/> and 
<Ref Func="RunExamples" BookName="gapdoc"/> for
automatic testing and correcting of manual examples.
</Item>   
</List> 
</Item>

<Item>
<Package>Gpd</Package> package by E.J. Moore and C.D. Wensley has been
substantially rewritten. The main extensions provide functions for:
<List>
<Item>
Subgroupoids of a direct product with complete graph groupoid, 
specified by a root group and choice of rays.
</Item>
<Item>
Automorphisms of finite groupoids - by object permutations; by root group 
automorphisms; and by ray images.
</Item>
<Item>
The automorphism group of a finite groupoid together with an isomorphism 
to a quotient of permutation groups.
</Item>
<Item>
Homogeneous groupoids (unions of isomorphic groupoids) and their 
morphisms, in particular homogeneous discrete groupoids: the latter 
are used in constructing crossed modules of groupoids in the 
<Package>XMod</Package> package.
</Item>
</List>
</Item>


<Item>
<Package>GRAPE</Package> package by L.H. Soicher:
<List>
<Item>
With much help from A. Hulpke, the interface between <Package>GRAPE</Package> 
and <F>dreadnaut</F> is now done entirely in &GAP; code. 
</Item>
<Item>
A 32-bit <F>nauty/dreadnaut</F> binary for Windows (XP and later) is 
included with <Package>GRAPE</Package>, so now <Package>GRAPE</Package> 
provides full functionality under Windows, with no installation necessary.
</Item>
<Item>
Graphs with ordered partitions of their vertices into <Q>colour-classes</Q>
are now handled by the graph automorphism group and isomorphism
testing functions.  An automorphism of a graph with colour-classes
is an automorphism of the graph which additionally preserves the list
of colour-classes (classwise), and an isomorphism from one graph with
colour-classes to a second is a graph isomorphism from the first graph
to the second which additionally maps the first list of colour-classes
to the second (classwise).
</Item>
<Item>
The &GAP; code and old standalone programs for the undocumented functions
<C>Enum</C> and <C>EnumColadj</C> have been removed as their functionality 
can now largely be handled by current documented &GAP; and 
<Package>GRAPE</Package> functions.
</Item>
</List>
</Item>

<Item>
<Package>IO</Package> package by M. Neunhöffer:
<List>
<Item>
New build system to allow for more flexibility regarding the use of
compiler options and adjusting to &GAP;&nbsp;4.5.
</Item>
<Item>
New functions to access time like <C>IO_gettimeofday</C>,
<C>IO_gmtime</C> and <C>IO_localtime</C>.
</Item>
<Item> Some parallel skeletons built on <C>fork</C> like: <C>ParListByFork</C>,
<C>ParMapReduceByFork</C>, <C>ParTakeFirstResultByFork</C> and
<C>ParWorkerFarmByFork</C>.
</Item>
<Item>
<C>IOHub</C> objects for automatic I/O multiplexing.
</Item>
<Item>
New functions <C>IO_gethostbyname</C> and <C>IO_getsockname</C>.
</Item>
</List>
</Item>

<Item>
<Package>IRREDSOL</Package> package by B. Höfling now covers all irreducible 
soluble subgroups of <M>GL(n,q)</M> for <M>q^n &lt; 1000000</M> and primitive 
soluble permutation groups of degree <M>&lt; 1000000</M> (previously, the 
bound was <M>65536</M>). It also has faster group recognition and adds a 
few omissions for <M>GL(3,8)</M> and <M>GL(6,5)</M>.
</Item>

<Item>
<Package>ParGAP</Package> package by G. Cooperman is now compiled
using a system-wide MPI implementation by default to facilitate running
it on proper clusters. There is also an option to build it with 
the <Package>MPINU</Package> library which is still supplied with the 
package (thanks to P. Smith for upgrading <Package>ParGAP</Package>
build process).
</Item>

<Item>
<Package>OpenMath</Package> package by M. Costantini, A. Konovalov, 
M. Nicosia and A. Solomon now supports much more OpenMath symbols
to facilitate communication by the remote procedure call protocol 
implemented in the <Package>SCSCP</Package> package.
Also, a third-party external library to support binary OpenMath encoding 
has been replaced by a proper implementation made entirely in &GAP;.
</Item>

<Item>
<Package>Orb</Package> package by J. Müller, M. Neunhöffer and F. Noeske:
<P/>
There have been numerous improvements to this package:
<List>
<Item>
A new fast implementation of AVL trees (balanced binary trees) in C.
</Item>
<Item>
New interface to hash table functionality and implementation in C for speedup.
</Item>
<Item>
Some new hash functions for various object types like transformations.
</Item>
<Item>
New function <C>ORB_EstimateOrbitSize</C> using the birthday paradox.
</Item>
<Item>
Improved functionality for product replacer objects.
</Item>
<Item>
New <Q>tree hash tables</Q>.
</Item>
<Item>
New functionality to compute weak and strong orbits for semigroups and monoids.
</Item>
<Item>
<C>OrbitGraph</C> for Orb orbits.
</Item>
<Item>
Fast C kernel methods for the following functions:
<P/>
<C>PermLeftQuoTransformationNC</C>,
<C>MappingPermSetSet</C>, <C>MappingPermListList</C>,
<C>ImageSetOfTransformation</C>,
and <C>KernelOfTransformation</C>.
</Item>
<Item>
New build system to allow for more flexibility regarding the use of
compiler options and to adjust to &GAP;&nbsp;4.5.
</Item>
</List>
</Item>

<Item>
<Package>RCWA</Package> package by S. Kohl among the new features and 
other improvements has the following:
<List>
<Item>
A database of all 52394 groups generated by 3 class transpositions of
<M>&ZZ;</M> which interchange residue classes with modulus less than
or equal to 6. This database contains the orders and the moduli of all
of these groups. Also it provides information on what is known about
which of these groups are equal and how their finite and infinite
orbits on <M>&ZZ;</M> look like.
</Item>
<Item>
More routines for investigating the action of an rcwa group on <M>&ZZ;</M>.
Examples are a routine which attempts to find out whether a given rcwa
group acts transitively on the set of nonnegative integers in its
support and a routine which looks for finite orbits on the set of all
residue classes of <M>&ZZ;</M>.
</Item>
<Item>
Ability to deal with rcwa permutations of <M>&ZZ;^2</M>.
</Item>
<Item>
Important methods have been made more efficient in terms of runtime
and memory consumption.
</Item>
<Item>
The output has been improved. For example, rcwa permutations are now
<C>Display</C>'ed in ASCII text resembling &LaTeX; output.
</Item>
</List>
</Item>

<Item>
The <Package>XGAP</Package> package by F. Celler and M. Neunhöffer can now 
be used on 64-bit architectures (thanks to N. Eldredge and M. Horn for 
sending patches). Furthermore, there is now an export to XFig option 
(thanks to Russ Woodroofe for this patch). The help system in 
<Package>XGAP</Package> has been adjusted to &GAP;&nbsp;4.5.
</Item>

<Item>
<Index>Packages under Windows</Index>
Additionally, some packages with kernel modules or external binaries 
are now available in Windows. The <F>-win.zip</F> archive and the
&GAP; installer for Windows include working versions of the following 
packages: <Package>Browse</Package>, <Package>cvec</Package>, 
<Package>EDIM</Package>, <Package>GRAPE</Package>, <Package>IO</Package>
and <Package>orb</Package>, which were previously unavailable for
Windows users.
</Item>
</List>

Finally, the following packages are withdrawn:
<List>
<Item>
<Package>IF</Package> package by M. Costantini is unmaintained and no
longer usable. More advanced functionality for interfaces to other computer 
algebra systems is now available in the <Package>SCSCP</Package> 
package by A. Konovalov and S. Linton.
</Item>
<Item>
<Package>Monoid</Package> package by J. Mitchell is superseded by 
the <Package>Citrus</Package> package by the same author.
</Item>
<Item>
<Package>NQL</Package> package by R. Hartung has been withdrawn by the author. 
</Item>
</List>

</Subsection>

</Section>


<Section Label="fix455"> 

<Heading>&GAP; 4.5.5 (July 2012)</Heading>


Fixed bugs which could lead to crashes:
<List>              
<Item>
For small primes (compact fields) <C>ZmodnZObj(r,p)</C> now 
returns the corresponding FFE to avoid crashes when compacting 
matrices. 
[Reported by Ignat Soroko]
</Item>
</List>

Other fixed bugs:

<List>
<Item>
Fixed a bug in <Ref Attr="CommutatorSubgroup" BookName="ref"/> for fp groups 
causing infinite recursion, which could, for example, be triggered 
by computing automorphism groups.
</Item>
<Item>
Previously, the list of factors of a polynomial was mutable, and hence could
be accidentally corrupted by callers. Now the list of irreducible factors 
is stored immutable. To deal with implicit reliance on old code, always a
shallow copy is returned. 
[reported by Jakob Kroeker]
</Item>
<Item>
Computing high powers of matrices ran into an error for matrices in the
format of the <Package>cvec</Package> package. Now the library function 
also works with these matrices.
[reported by Klaus Lux]
</Item>
<Item>
The pseudo tty code which is responsible for spawning subprocesses has been 
partially rewritten to allow more than 128 subprocesses on certain systems.
This mechanism is for example used by <Package>ANUPQ</Package> and 
<Package>nq</Package> packages to compute group quotients via an external 
program. Previously, on Mac OS X this could be done precisely 128 times, 
and then an error would occur. That is, one could e.g. compute 128 nilpotent 
quotients, and then had to restart &GAP; to compute more. This also affected 
other systems, such as OpenBSD, where it now also works correctly.
</Item>
<Item>
On Mac OS X, using &GAP; compiled against GNU readline 6.2, pasting text
into the terminal session would result in this text appearing very slowly,
with a 0.1 sec delay between each <Q>keystroke</Q>. This is not the case with
versions 6.1 and older, and has been reported to the GNU readline team. In
the meantime, we work around this issue in most situations by setting
<C>rl_event_hook</C> only if <C>OnCharReadHookActive</C> is set.
</Item>
<Item>
<Ref Func="ShowUserPreferences" BookName="ref"/> ran into a break loop in 
case of several undeclared user preferences. [Reported by James Mitchell]
</Item>
<Item>
&GAP; did not start correctly if the user preference 
<C>"InfoPackageLoadingLevel"</C> was set to a number <M> >= 3</M>. 
The reason is that <C>PrintFormattedString</C> was called before 
it was installed. The current fix is a temporary solution. 
</Item>
<Item>
The <C>"hints"</C> member of <C>TypOutputFile</C> used to contain 3*100 entries, 
yet <C>addLineBreakHint</C> would write entries with index up to and including 
3*99+3=300, leading to a buffer overflow. This would end up overwriting 
the <C>"stream"</C> member with -1. Fixed by incrementing the size of 
<C>"hints"</C> to 301. 
[Reported by Jakob Kroeker]
</Item>
<Item>
The function <C>IsDocumentedWord</C> tested the given word against 
strings obtained by splitting help matches at non-letter characters.
This way, variable names containing underscores or digits were erroneously
not regarded as documented, and certain substrings of these names were 
erroneously regarded as documented.
</Item>
<Item>
On Windows, an error occurred if one tried to use the default Windows 
browser as a help viewer (see <Ref Func="SetHelpViewer" BookName="ref"/>). 
Now the browser opens the top of the correspoding manual chapter. The 
current fix is a temporary solution since the problem remains with the 
positioning at the required manual section.
</Item>
</List>


Improved functionality:
<List>              
<Item>
<Ref Func="WriteGapIniFile" BookName="ref"/> on Windows now produces the
<File>gap.ini</File> file with Windows style line breaks. Also, an info 
message is now printed if an existing <File>gap.ini</File> file was moved 
to a backup file <File>gap.ini.bak</File>.
</Item>
<Item>
The <Package>CTblLib</Package> and <Package>TomLib</Package> packages are 
removed from the list of suggested packages of the core part of &GAP;. 
Instead they are added to the default list of the user preference 
<C>"PackagesToLoad"</C>. This way it is possible to configure &GAP; to not 
load these packages via changing the default value of <C>"PackagesToLoad"</C>.
</Item>
<Item>
The conjugacy test in <M>S_n</M> for intransitive subgroups was improved.
This deals with inefficiency issue in the case reported by Stefan Kohl.
</Item>
<Item>
Added <C>InstallAndCallPostRestore</C> to <File>lib/system.g</File> and call
it in <File>lib/init.g</File> instead of <C>CallAndInstallPostRestore</C> for 
the function that reads the files listed in &GAP; command line. This fixes 
the problem reported by Yevgen Muntyan when 
<Ref Func="SaveWorkspace" BookName="ref"/> was used in a file listed in &GAP; 
command line (before, according to the documentation, 
<Ref Func="SaveWorkspace" BookName="ref"/> was only 
allowed at the main &GAP; prompt).
</Item>
<Item>
There is now a new user preference <C>PackagesToIgnore</C>,
see <Ref Func="SetUserPreference" BookName="ref"/>. It contains
a list of names of packages that shall be regarded as not available
at all in the current session, both for autoloading and for later calls
of <Ref Func="LoadPackage" BookName="ref"/>. This preference is useful 
for testing purposes if one wants to run some code without loading 
certain packages.
</Item>
</List>

</Section>



<Section Label="fix456"> 

<Heading>&GAP; 4.5.6 (September 2012)</Heading>

Improved functionality:
<List>              
<Item>
The argument of <Ref Func="SaveWorkspace" BookName="ref"/> can now start 
with <C>~/</C> which is expanded to the users home directory.
</Item>
<Item>
Added the method for <Ref Oper="Iterator" BookName="ref"/> for 
<Ref Var="PositiveIntegers" BookName="ref"/>.
[Suggested by Attila Egri-Nagy].
</Item>
<Item>
Changed kernel tables such that list access functionality for
<C>T_SINGULAR</C> objects can be installed by methods at the &GAP; level.
</Item>
<Item>
In case of saved history, <Q>UP</Q> arrow after starting &GAP; yields 
last stored line. The user preference <C>HistoryMaxLines</C> is now used
when storing and saving history (see 
<Ref Func="SetUserPreference" BookName="ref"/>).
</Item>
</List>

Fixed bugs which could lead to crashes:
<List>              
<Item>
A crash occuring during garbage collection following a call to 
<C>AClosVec</C> for a <C>GF(2)</C> code.
[Reported by Volker Braun]
</Item>
<Item>
A crash when parsing certain syntactically invalid code.
[Reported by multiple users]
</Item>
<Item>
Fixed and improved command line editing without readline support.
Fixed a segfault which could be triggered by a combination of 
<Q>UP</Q> and <Q>DOWN</Q> arrows.
[Reported by James Mitchell]
</Item>
<Item>
Fixed a bug in the kernel code for floats that caused a crash 
on SPARC Solaris in 32-bit mode.
[Reported by Volker Braun]
</Item>
</List>

Other fixed bugs:

<List>
<Item>
Very large (more than 1024 digit) integers were not being coded correctly
in function bodies unless the integer limb size was 16 bits. 
[Reported by Stefan Kohl]
</Item>
<Item>
An old variable was used in assertion, causing errors in a debugging 
compilation.
[Reported by Volker Braun]
</Item>
<Item>
The environment variable <C>PAGER</C> is now correctly interpreted when it
contains the full path to the pager program. Furthermore, if the external 
pager <C>less</C> is found from the environment it is made sure that the 
option <C>-r</C> is used (same for <C>more -f</C>).
[Reported by Benjamin Lorenz]
</Item>
<Item>
Fixed a bug in <C>PermliftSeries</C>.
[Reported by Aiichi Yamasaki]
</Item>
<Item>
Fixed discarder function in lattice computation to distinguish 
general and zuppo discarder.
[Reported by Leonard Soicher]
</Item>
<Item>
The <Ref Func="GL" Label="for dimension and a ring" BookName="ref"/> and 
<Ref Func="SL" Label="for dimension and a ring" BookName="ref"/> 
constructors did not correctly handle <C>GL(filter,dim,ring)</C>.
</Item>
<Item>
The names of two primitive groups of degree 64 were incorrect.
</Item>
<Item>
The <Ref Oper="\in" Label="operation for testing membershi" BookName="ref"/> 
method for groups handled by a nice monomorphism sometimes could produce 
an error in situations where it should return false. This only happened 
when using <C>SeedFaithfulAction</C> to influence how 
<Ref Oper="NiceMonomorphism" BookName="ref"/>
builds the nice monomorphims for a matrix groups.
</Item>
<Item>
Wrong <Ref Oper="PrintObj" BookName="ref"/> method was removed to
fix delegations accordingly to <Ref Sect="View and Print" BookName="ref"/>.
</Item>
<Item>
Fixed a method for <Ref Oper="Coefficients" BookName="ref"/> which,
after Gaussian elimination, did not check that the coefficients
actually lie in the left-acting-domain of the vector space. This
could lead to a wrong answer in a vector space membership test.
[Reported by Kevin Watkins]
</Item>
</List>

Improved documentation:

<List>
<Item>
Removed outdated statements from the documentation of 
<Ref Func="StructureDescription" BookName="ref"/>
which now non-ambiguosly states that <C>StructureDescription</C> is not an 
isomorphism invariant: non-isomorphic groups can have the same string 
value, and two isomorphic groups in different representations can produce 
different strings.
</Item>
<Item>
&GAP; now allows overloading of a loaded help book by another one. In this
case, only a warning is printed and no error is raised. This makes sense 
if a book of a not loaded package is loaded in a workspace and then &GAP; 
is started with a root path that contains a newer version. 
[Reported by Sebastian Gutsche]
</Item>
<Item>
Provided a better description of user preferences mechanism
(<Ref Sect="Configuring User preferences" BookName="ref"/>) and a hint to
familiarise with them using <Ref Func="WriteGapIniFile" BookName="ref"/>
function to create a file which contains descriptions of all known user
preferences and also sets those user preferences which currently do not
have their default value. One can then edit that file to customize
(further) the user preferences for future &GAP; sessions.
</Item>
</List>

New packages added for the redistribution with &GAP;:
<List>
<Item>
<Package>AutoDoc</Package> package by S. Gutsche,
providing tools for automated generation of <Package>GAPDoc</Package> manuals.
</Item>
<Item>
<Package>Convex</Package> package by S. Gutsche,
which provides structures and algorithms for convex geometry. 
</Item>
<Item>
<Package>PolymakeInterface</Package> package by T. Baechler and S. Gutsche, 
providing a link to the callable library of the <Package>polymake</Package> 
system (<URL>http://www.polymake.org</URL>).
</Item>
<Item>
<Package>ToolsForHomalg</Package> package by M. Barakat, S. Gutsche and
M. Lange-Hegermann, which provides some auxiliary functionality for the
<Package>homalg</Package> project (<URL>http://homalg.math.rwth-aachen.de/</URL>).
</Item>
</List>

</Section>


<Section Label="fix457"> 

<Heading>&GAP; 4.5.7 (December 2012)</Heading>

Fixed bugs which could lead to crashes:
<List>              
<Item>Closing with <C>LogInputTo</C> (or <C>LogOutputTo</C>)
a logfile opened with <Ref Func="LogTo" BookName="ref"/> 
left the data structures corrupted, resulting in a crash.
</Item>
<Item>
On 32-bit systems we can have long integers <C>n</C> such that 
<C>Log2Int(n)</C> is not an immediate integer. In such cases 
<C>Log2Int</C> gave wrong or corrupted
results which in turn could crash &GAP;, e.g., in <C>ViewObj(n)</C>.
</Item>
<Item>
Some patterns of use of <Ref Func="UpEnv" BookName="ref"/> and 
<Ref Func="DownEnv" BookName="ref"/> were leading to a segfault.
</Item>
</List>

Other fixed bugs:

<List>
<Item>
Viewing of long negative integers was broken, because it went into a break loop.
</Item>
<Item>
Division by zero in <Ref Func="ZmodnZ" BookName="ref"/> (<M>n</M> not prime) 
produced invalid objects. [Reported by Mark Dickinson]
</Item>
<Item>
Fixed a bug in determining multiplicative inverse for a zero polynomial.
</Item>
<Item>
Fixed a bug causing infinite recursion in <Ref Oper="NaturalHomomorphismByNormalSubgroup" BookName="ref"/>.
</Item>
<Item>
A workaround was added to deal with a package method creating pcgs for permutation 
groups for which the entry <C>permpcgsNormalSteps</C> is missing.
</Item>
<Item>
For a semigroup of associative words that is not the full semigroup of
all associative words, the methods for <Ref Oper="Size" BookName="ref"/> 
and <Ref Oper="IsTrivial" BookName="ref"/> called one another causing 
infinite recursion. 
</Item>
<Item>
The 64-bit version of the <F>gac</F> script produced wrong (>= 2^31) CRC 
values because of an integer conversion problem.
</Item>
<Item>
It was not possible to compile &GAP; on some systems where <C>HAVE_SELECT</C> detects as false.
</Item>
<Item>
Numbers in memory options on the command line exceeding 2^32 could not be
parsed correctly, even on 64-bit systems. [Reported by Volker Braun]
</Item>
</List>

New packages added for the redistribution with &GAP;:
<List>
<Item>
<Package>Float</Package> package by L. Bartholdi, which extends &GAP;
floating-point capabilities by providing new floating-point handlers for 
high-precision real, interval and complex arithmetic using MPFR, MPFI, 
MPC or CXSC external libraries. It also contains a very high-performance 
implementation of the LLL (Lenstra-Lenstra-Lovász) lattice reduction 
algorithm via the external library FPLLL. 
</Item>
<Item>
<Package>ToricVarieties</Package> package by S. Gutsche,
which provides data structures to handle toric varieties by their 
commutative algebra structure and by their combinatorics. 
</Item>
</List>

</Section>


</Chapter>


<!-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% --> 
<!-- %% --> 
<!-- %E -->