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<div class="ChapSects"><a href="chap4.html#X837AADDA7EA9A541">4 <span class="Heading">Changes between <strong class="pkg">GAP</strong> 4.4 and <strong class="pkg">GAP</strong> 4.5</span></a>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap4.html#X7DA602757C152B0C">4.1 <span class="Heading">Changes in the core <strong class="pkg">GAP</strong> system introduced in <strong class="pkg">GAP</strong> 4.5</span></a>
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<div class="ContSSBlock">
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap4.html#X84FC44718386FA1A">4.1-1 <span class="Heading">Improved functionality</span></a>
</span>
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap4.html#X7E24E9DE7CADD1B7">4.1-2 <span class="Heading">Changes in distribution formats</span></a>
</span>
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap4.html#X80AB8641792E74C9">4.1-3 <span class="Heading">Improvements to the user interface</span></a>
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<span class="ContSS"><br /><span class="nocss"> </span><a href="chap4.html#X81318FC0873923C3">4.1-4 <span class="Heading">Better documentation</span></a>
</span>
</div></div>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap4.html#X85D796968453CFBF">4.2 <span class="Heading">Packages in <strong class="pkg">GAP</strong> 4.5</span></a>
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<div class="ContSSBlock">
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap4.html#X7E8089C881AB6BA1">4.2-1 <span class="Heading">Interface between the core system and packages</span></a>
</span>
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap4.html#X81A313117C30EC28">4.2-2 <span class="Heading">New and updated packages since <strong class="pkg">GAP</strong> 4.4.12</span></a>
</span>
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<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap4.html#X83D3FC7781921387">4.3 <span class="Heading"><strong class="pkg">GAP</strong> 4.5.5 (July 2012)</span></a>
</span>
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<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap4.html#X79311F9185A267DB">4.4 <span class="Heading"><strong class="pkg">GAP</strong> 4.5.6 (September 2012)</span></a>
</span>
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<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap4.html#X81528B5F78B996D2">4.5 <span class="Heading"><strong class="pkg">GAP</strong> 4.5.7 (December 2012)</span></a>
</span>
</div>
</div>
<h3>4 <span class="Heading">Changes between <strong class="pkg">GAP</strong> 4.4 and <strong class="pkg">GAP</strong> 4.5</span></h3>
<p>This chapter lists most important changes between <strong class="pkg">GAP</strong> 4.4.12 and the first public release of <strong class="pkg">GAP</strong> 4.5. It also contains information about subsequent update releases for <strong class="pkg">GAP</strong> 4.5. It is not meant to serve as a complete account on all improvements; instead, it should be viewed as an introduction to <strong class="pkg">GAP</strong> 4.5, accompanying its release announcement.</p>
<p><a id="X7DA602757C152B0C" name="X7DA602757C152B0C"></a></p>
<h4>4.1 <span class="Heading">Changes in the core <strong class="pkg">GAP</strong> system introduced in <strong class="pkg">GAP</strong> 4.5</span></h4>
<p>In this section we list most important new features and bugfixes in the core system introduced in <strong class="pkg">GAP</strong> 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 <a href="chap4.html#X85D796968453CFBF"><span class="RefLink">4.2</span></a>.</p>
<p><a id="X84FC44718386FA1A" name="X84FC44718386FA1A"></a></p>
<h5>4.1-1 <span class="Heading">Improved functionality</span></h5>
<p>Performance improvements:</p>
<ul>
<li><p>The <strong class="pkg">GAP</strong> kernel now uses <strong class="pkg">GMP</strong> (GNU multiple precision arithmetic library, <span class="URL"><a href="http://gmplib.org/">http://gmplib.org/</a></span>) for faster large integer arithmetic.</p>
</li>
<li><p>Improved performance for records with large number of components.</p>
</li>
<li><p>Speedup of hash tables implementation at the <strong class="pkg">GAP</strong> library level.</p>
</li>
<li><p><code class="func">MemoryUsage</code> (<a href="../../doc/ref/chap12.html#X7F4D216B7DF7BE9D"><span class="RefLink">Reference: MemoryUsage</span></a>) is now much more efficient, in particular for large objects.</p>
</li>
<li><p>Speedups in the computation of low index subgroups, Tietze transformations, calculating high powers of matrices over finite fields, <code class="func">Factorial</code> (<a href="../../doc/ref/chap16.html#X87665F748594BF29"><span class="RefLink">Reference: Factorial</span></a>), etc.</p>
</li>
</ul>
<p>New and improved kernel functionality:</p>
<ul>
<li><p>By default, the <strong class="pkg">GAP</strong> kernel compiles with the <strong class="pkg">GMP</strong> and <strong class="pkg">readline</strong> libraries. The <strong class="pkg">GMP</strong> library is supplied with <strong class="pkg">GAP</strong> 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 <strong class="pkg">GAP</strong> kernel with the system <strong class="pkg">GMP</strong> if your system has it. The <strong class="pkg">readline</strong> library must be installed on your system in advance to be used with <strong class="pkg">GAP</strong>.</p>
</li>
<li><p>Floating point literals are now supported in the <strong class="pkg">GAP</strong> language, so that, floating point numbers can be entered in <strong class="pkg">GAP</strong> expressions in a natural way. Support for floats is now properly documented, see <a href="../../doc/ref/chap19.html#X81AA901181CA568F"><span class="RefLink">Reference: Floats</span></a>. <strong class="pkg">GAP</strong> 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.</p>
</li>
<li><p>The Mersenne twister random number generator has been made independent of endianness, so that random seeds can now be transferred between architectures. See <a href="../../doc/ref/chap14.html#X7F772E2686B35865"><span class="RefLink">Reference: GlobalMersenneTwister</span></a> for details.</p>
</li>
<li><p>Defaults for <code class="code">-m</code> and <code class="code">-o</code> options have been increased. Changes have been made to the way that <strong class="pkg">GAP</strong> obtains memory from the Operating System, to make <strong class="pkg">GAP</strong> more compatible with C libraries. A new <code class="code">-s</code> option has been introduced to control or turn off the new behaviour, see <a href="../../doc/ref/chap3.html#X782751D5858A6EAF"><span class="RefLink">Reference: Command Line Options</span></a>.</p>
</li>
<li><p>The filename and lines from which a function was read can now be recovered using <code class="func">FilenameFunc</code> (<a href="../../doc/ref/chap5.html#X80E108C57F90FAA3"><span class="RefLink">Reference: FilenameFunc</span></a>), <code class="func">StartlineFunc</code> (<a href="../../doc/ref/chap5.html#X7FF7643781D2C194"><span class="RefLink">Reference: StartlineFunc</span></a>) and <code class="func">EndlineFunc</code> (<a href="../../doc/ref/chap5.html#X7FF7643781D2C194"><span class="RefLink">Reference: EndlineFunc</span></a>). This allows you, for example, to implement a function such as <code class="func">PageSource</code> (<a href="../../doc/ref/chap5.html#X845A929B83D46E01"><span class="RefLink">Reference: PageSource</span></a>) to show the file containing the source code of a function or a method in a pager, see <code class="func">Pager</code> (<a href="../../doc/ref/chap2.html#X7ED03E41792C3840"><span class="RefLink">Reference: Pager</span></a>).</p>
</li>
<li><p><code class="func">CallFuncList</code> (<a href="../../doc/ref/chap5.html#X7CF4DDB97D65AE52"><span class="RefLink">Reference: CallFuncList</span></a>) was made into an operation so that it can be used to define behaviour of a non-function when called as a function.</p>
</li>
<li><p>Improvements to the cyclotomic number arithmetic for fields with large conductors.</p>
</li>
<li><p>Better and more flexible viewing of some large objects.</p>
</li>
<li><p>Opportunity to interrupt some long kernel computations, e.g. multiplication of compressed matrices, intercepting <code class="code">Ctrl-C</code> in designated places in the kernel code by means of a special kernel function for that purpose.</p>
</li>
<li><p><code class="code">ELM_LIST</code> now allows you to install methods where the second argument is NOT a positive integer.</p>
</li>
<li><p>Kernel function <code class="func">DirectoryContents</code> (<a href="../../doc/ref/chap9.html#X7B225E5282534EDA"><span class="RefLink">Reference: DirectoryContents</span></a>) to get the list of names of files and subdirectories in a directory.</p>
</li>
<li><p>Kernel functions for Kronecker product of compressed matrices, see <code class="func">KroneckerProduct</code> (<a href="../../doc/ref/chap24.html#X8634C79E7DB22934"><span class="RefLink">Reference: KroneckerProduct</span></a>).</p>
</li>
</ul>
<p>New and improved library functionality:</p>
<ul>
<li><p>Extensions of data libraries:</p>
<ul>
<li><p>Functions and iterators are now available to create and enumerate simple groups by their order up to isomorphism: <code class="func">SimpleGroup</code> (<a href="../../doc/ref/chap39.html#X8492B05B822AC58C"><span class="RefLink">Reference: SimpleGroup</span></a>), <code class="func">SmallSimpleGroup</code> (<a href="../../doc/ref/chap39.html#X872E93F586F54FCE"><span class="RefLink">Reference: SmallSimpleGroup</span></a>), <code class="func">SimpleGroupsIterator</code> (<a href="../../doc/ref/chap39.html#X839CDD8C7AE39FD6"><span class="RefLink">Reference: SimpleGroupsIterator</span></a>) and <code class="func">AllSmallNonabelianSimpleGroups</code> (<a href="../../doc/ref/chap39.html#X7EB47BF27D8CBF72"><span class="RefLink">Reference: AllSmallNonabelianSimpleGroups</span></a>).</p>
</li>
<li><p>See also packages <strong class="pkg">CTblLib</strong>, <strong class="pkg">IRREDSOL</strong> and <strong class="pkg">Smallsemi</strong> listed in Section <a href="chap4.html#X81A313117C30EC28"><span class="RefLink">4.2-2</span></a>.</p>
</li>
</ul>
</li>
<li><p>Many more methods are now available for the built-in floating point numbers, see <a href="../../doc/ref/chap19.html#X81AA901181CA568F"><span class="RefLink">Reference: Floats</span></a>.</p>
</li>
<li><p>The bound for the proper primality test in <code class="func">IsPrimeInt</code> (<a href="../../doc/ref/chap14.html#X78FDA4437EDCA70C"><span class="RefLink">Reference: IsPrimeInt</span></a>) increased up to <span class="SimpleMath">10^18</span>.</p>
</li>
<li><p>Improved code for determining transversal and double coset representatives in large groups.</p>
</li>
<li><p>Improvements in <code class="func">Normalizer</code> (<a href="../../doc/ref/chap39.html#X87B5370C7DFD401D"><span class="RefLink">Reference: Normalizer</span></a>) for <span class="SimpleMath">S_n</span>.</p>
</li>
<li><p>Smith normal form of a matrix may be computed over arbitrary euclidean rings, see <code class="func">NormalFormIntMat</code> (<a href="../../doc/ref/chap25.html#X81FB746E82BE6CDA"><span class="RefLink">Reference: NormalFormIntMat</span></a>).</p>
</li>
<li><p>Improved algorithms to determine the subgroup lattice of a group, as well as the function <code class="func">DotFileLatticeSubgroups</code> (<a href="../../doc/ref/chap39.html#X7E5DF287825EE7BA"><span class="RefLink">Reference: DotFileLatticeSubgroups</span></a>) to save the lattice structure in <code class="file">.dot</code> file to view it e.g. with <strong class="pkg">GraphViz</strong>.</p>
</li>
<li><p>Special teaching mode which simplifies some output and provides more basic functionality, see <a href="../../doc/ref/chap6.html#X87847E5087D6F47D"><span class="RefLink">Reference: Teaching Mode</span></a>.</p>
</li>
<li><p>Functionality specific for use in undergraduate abstract algebra courses, e.g. checksums (<a href="../../doc/ref/chap14.html#X7904B6D681EBF091"><span class="RefLink">Reference: Check Digits</span></a>); string/integer list conversion; rings of small orders; the function <code class="func">SetNameObject</code> (<a href="../../doc/ref/chap6.html#X87E546E27A1F1FAB"><span class="RefLink">Reference: SetNameObject</span></a>) to set display names for objects for more informative examples, e.g. constructing groups from "named" objects, such as, for example, <code class="code">R90</code> for a 90-degree rotation).</p>
</li>
<li><p>Functions <code class="func">DirectoryDesktop</code> (<a href="../../doc/ref/chap9.html#X86F4A32C83B82369"><span class="RefLink">Reference: DirectoryDesktop</span></a>) and <code class="func">DirectoryHome</code> (<a href="../../doc/ref/chap9.html#X7B0D818A808A3481"><span class="RefLink">Reference: DirectoryHome</span></a>) which provide uniform access to default directories under Windows, Mac OS X and Unix.</p>
</li>
<li><p>Improved methods for hashing when computing orbits.</p>
</li>
<li><p>Functionality to call external binaries under Windows.</p>
</li>
<li><p>Symplectic groups over residue class rings, see <code class="func">SymplecticGroup</code> (<a href="../../doc/ref/chap50.html#X8142A8B07811CA90"><span class="RefLink">Reference: SymplecticGroup</span></a>).</p>
</li>
<li><p>Basic version of the simplex algorithm for matrices.</p>
</li>
<li><p>New functions, operations and attributes: <code class="func">PrimeDivisors</code> (<a href="../../doc/ref/chap14.html#X80E7A5D381C64CC9"><span class="RefLink">Reference: PrimeDivisors</span></a>), <code class="func">Shuffle</code> (<a href="../../doc/ref/chap21.html#X8057372F83374193"><span class="RefLink">Reference: Shuffle</span></a>) for lists, <code class="func">IteratorOfPartitions</code> (<a href="../../doc/ref/chap16.html#X8793AEBD7E529E1D"><span class="RefLink">Reference: IteratorOfPartitions</span></a>), <code class="func">IteratorOfCombinations</code> (<a href="../../doc/ref/chap16.html#X78DD5C0D81057540"><span class="RefLink">Reference: IteratorOfCombinations</span></a>), <code class="func">EnumeratorOfCombinations</code> (<a href="../../doc/ref/chap16.html#X78DD5C0D81057540"><span class="RefLink">Reference: EnumeratorOfCombinations</span></a>) and others.</p>
</li>
<li><p>The behaviour of <code class="func">Info</code> (<a href="../../doc/ref/chap7.html#X864E4B6886E2697D"><span class="RefLink">Reference: Info</span></a>) statements can now be configured per info class, this applies to the way the arguments are printed and to the output stream, see <a href="../../doc/ref/chap7.html#X7A9C902479CB6F7C"><span class="RefLink">Reference: Info Functions</span></a>.</p>
</li>
<li><p>New function <code class="func">Test</code> (<a href="../../doc/ref/chap7.html#X87712F9D8732193C"><span class="RefLink">Reference: Test</span></a>) which is a more flexible and informative substitute of <code class="func">ReadTest</code> (<a href="../../doc/ref/chap7.html#X7DBA18E38405A147"><span class="RefLink">Reference: ReadTest</span></a>) operation.</p>
</li>
<li><p><code class="code">ConnectGroupAndCharacterTable</code> is replaced by more robust function <code class="func">CharacterTableWithStoredGroup</code> (<a href="../../doc/ref/chap71.html#X8788C6C7829C1ADE"><span class="RefLink">Reference: CharacterTableWithStoredGroup</span></a>).</p>
</li>
</ul>
<p>Many problems in <strong class="pkg">GAP</strong> have have been fixed, among them the following:</p>
<ul>
<li><p>Polynomial factorisation over rationals could miss factors of degree greater than <span class="SimpleMath">deg(f)/2</span> if they have very small coefficients, while the cofactor has large coefficients.</p>
</li>
<li><p><code class="func">IntermediateSubgroups</code> (<a href="../../doc/ref/chap39.html#X781661FB78DC83B5"><span class="RefLink">Reference: IntermediateSubgroups</span></a>) called on a group and a normal subgroup did not properly calculate maximal inclusion relationships.</p>
</li>
<li><p><code class="func">CentreOfCharacter</code> (<a href="../../doc/ref/chap72.html#X7E77D4147A0836D3"><span class="RefLink">Reference: CentreOfCharacter</span></a>) and <code class="func">ClassPositionsOfCentre</code> (<a href="../../doc/ref/chap72.html#X7CE5B4137B399274"><span class="RefLink">Reference: ClassPositionsOfCentre (for a character)</span></a>) called for a group character could return a perhaps too large result.</p>
</li>
<li><p><code class="func">Trace</code> (<a href="../../doc/ref/chap58.html#X7DD17EB581200AD6"><span class="RefLink">Reference: Traces of field elements and matrices</span></a>) called for an element of a finite field that was created with <code class="func">AlgebraicExtension</code> (<a href="../../doc/ref/chap67.html#X7CDA90537D2BAC8A"><span class="RefLink">Reference: AlgebraicExtension</span></a>) ran into an error.</p>
</li>
<li><p><code class="func">IrreducibleRepresentationsDixon</code> (<a href="../../doc/ref/chap71.html#X8493ED7A86FFCB8A"><span class="RefLink">Reference: IrreducibleRepresentationsDixon</span></a>) did not accept a list with one character as a second argument.</p>
</li>
<li><p>Composing a homomorphism from a permutation group to a finitely presented group with another homomorphism could give wrong results.</p>
</li>
<li><p>For certain arguments, the function <code class="func">EU</code> (<a href="../../doc/ref/chap18.html#X842338F184E63894"><span class="RefLink">Reference: EU</span></a>) returned wrong results.</p>
</li>
<li><p>In the table of marks of cyclic groups, <code class="func">NormalizersTom</code> (<a href="../../doc/ref/chap70.html#X7CE6C45881F7F7D4"><span class="RefLink">Reference: NormalizersTom</span></a>) value was wrong.</p>
</li>
<li><p>The function <code class="func">PermChars</code> (<a href="../../doc/ref/chap72.html#X7D02541482C196A6"><span class="RefLink">Reference: PermChars</span></a>) 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.</p>
</li>
<li><p><strong class="pkg">GAP</strong> crashed when the intersection of ranges became empty.</p>
</li>
<li><p><code class="code">IsPSL</code>, and in turn <code class="func">StructureDescription</code> (<a href="../../doc/ref/chap39.html#X8199B74B84446971"><span class="RefLink">Reference: StructureDescription</span></a>), erroneously recognised non-PSL groups of the right order as PSL.</p>
</li>
<li><p>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.</p>
</li>
<li><p>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.</p>
</li>
<li><p>Constant polynomials were not recognised as univariate in any variable.</p>
</li>
<li><p>The kernel recursion depth counter was not reset properly when running into many break loops.</p>
</li>
<li><p><strong class="pkg">GAP</strong> did not behave well when printing of a (large) object was interrupted with <code class="code">Ctrl-C</code>. Now the object is no longer corrupted and the indentation level is reset.</p>
</li>
</ul>
<p>Potentially incompatible changes:</p>
<ul>
<li><p>The zero polynomial now has degree <code class="code">-infinity</code>, see <code class="func">DegreeOfLaurentPolynomial</code> (<a href="../../doc/ref/chap66.html#X78AF77C383245254"><span class="RefLink">Reference: DegreeOfLaurentPolynomial</span></a>).</p>
</li>
<li><p>Multiple unary <code class="code">+</code> or <code class="code">-</code> signs are no longer allowed (to avoid confusion with increment/decrement operators from other programming languages).</p>
</li>
<li><p>Due to changes to improve the performance of records with large number of components, the ordering of record components in <code class="code">View</code>'ed records has changed.</p>
</li>
<li><p>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 <span class="SimpleMath">GF(2)</span> and then assign an element of <span class="SimpleMath">GF(4)</span> to one of its entries.</p>
</li>
</ul>
<p>No longer supported:</p>
<ul>
<li><p>Completion files mechanism.</p>
</li>
<li><p><strong class="pkg">GAP</strong> 3 compatibility mode.</p>
</li>
</ul>
<p>In addition, we no longer recommend using the <strong class="pkg">GAP</strong> compiler <code class="file">gac</code> to compile <strong class="pkg">GAP</strong> code to <strong class="pkg">C</strong>, and may withdraw it in future releases. Compiling <strong class="pkg">GAP</strong> 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 <strong class="pkg">C</strong> and loading them into the kernel as described in <code class="func">LoadDynamicModule</code> (<a href="../../doc/ref/chap76.html#X7C99782886B18C77"><span class="RefLink">Reference: LoadDynamicModule</span></a>). The <code class="file">gac</code> script will remain available as a convenient way of compiling such kernel modules from <strong class="pkg">C</strong>.</p>
<p>Also, the following functions and operations were made obsolete: <code class="code">AffineOperation</code>, <code class="code">AffineOperationLayer</code>, <code class="code">FactorCosetOperation</code>, <code class="code">DisplayRevision</code>, <code class="code">ProductPol</code>, <code class="code">TeXObj</code>, <code class="code">LaTeXObj</code>.</p>
<p><a id="X7E24E9DE7CADD1B7" name="X7E24E9DE7CADD1B7"></a></p>
<h5>4.1-2 <span class="Heading">Changes in distribution formats</span></h5>
<p>The <strong class="pkg">GAP</strong> 4.5 source distribution has the form of a single archive containing the core system and the most recent "stable" versions of all currently redistributed packages. There are no optional archives to download: the <strong class="pkg">TomLib</strong> 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 <code class="file">tools</code> archive is now included as an archive in the <code class="file">etc</code> directory. To unpack and install the archive, user the script <code class="file">etc/install-tools.sh</code>.</p>
<p>We no longer distribute separate bugfix archives when the core <strong class="pkg">GAP</strong> system changes, or updated packages archives when a redistributed package is updated. Instead, the single <strong class="pkg">GAP</strong> source distribution archive will be labelled by the version of the core <strong class="pkg">GAP</strong> 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 <strong class="pkg">GAP</strong> installation, and rebuild binaries for the <strong class="pkg">GAP</strong> 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 <strong class="pkg">GAP</strong> installation.</p>
<p>Furthermore, by default <strong class="pkg">GAP</strong> will now automatically read a user-specific <strong class="pkg">GAP</strong> root directory (unless <strong class="pkg">GAP</strong> is called with the <code class="code">-r</code> 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 <a href="chap4.html#X80AB8641792E74C9"><span class="RefLink">4.1-3</span></a> below for more details). Private packages can also be installed in this directory for the same reason.</p>
<p>There are some changes in archive formats used for the distribution: we continue to provide <code class="file">.tar.gz</code>, <code class="file">.tar.bz2</code> and <code class="file">-win.zip</code> archives. We have added <code class="file">.zip</code>, and stopped providing <code class="file">.zoo</code> 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>
<p>With the release of <strong class="pkg">GAP</strong> 4.5, we also encourage more users to take advantage of the increasingly mature binary distributions which are now available. These include:</p>
<ul>
<li><p>The binary <code class="file">rsync</code> distribution for <strong class="pkg">GAP</strong> on Linux PCs with i686 or x86_64 compatible processors provided by Frank Lübeck, see <span class="URL"><a href="http://www.math.rwth-aachen.de/~Frank.Luebeck/gap/rsync">http://www.math.rwth-aachen.de/~Frank.Luebeck/gap/rsync</a></span>.</p>
</li>
<li><p><strong class="pkg">BOB</strong>, a tool for Linux and Mac OS X to download and build <strong class="pkg">GAP</strong> and its packages from source provided by M. Neunhöffer: <span class="URL"><a href="http://www-groups.mcs.st-and.ac.uk/~neunhoef/Computer/Software/Gap/bob.html">http://www-groups.mcs.st-and.ac.uk/~neunhoef/Computer/Software/Gap/bob.html</a></span>.</p>
</li>
<li><p>The <strong class="pkg">GAP</strong> installer for Windows provided by Alexander Konovalov: <span class="URL"><a href="http://www.gap-system.org/ukrgap/wininst/">http://www.gap-system.org/ukrgap/wininst/</a></span>.</p>
</li>
</ul>
<p>In the near future, we also hope to have a binary distribution for Mac OS X.</p>
<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 <strong class="pkg">Example</strong> 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 <strong class="pkg">GAP</strong> website.</p>
<p><a id="X80AB8641792E74C9" name="X80AB8641792E74C9"></a></p>
<h5>4.1-3 <span class="Heading">Improvements to the user interface</span></h5>
<p>By default, <strong class="pkg">GAP</strong> now uses the <strong class="pkg">readline</strong> 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 <a href="../../doc/ref/chap6.html#X7E95EB017803F53C"><span class="RefLink">Reference: Editing using the readline library</span></a>.</p>
<p>We have extended facilities for user interface customisation. By default <strong class="pkg">GAP</strong> automatically scans a user specific <strong class="pkg">GAP</strong> root directory (unless <strong class="pkg">GAP</strong> is called with the <code class="code">-r</code> option). The name of this user specific directory depends on the operating system and is contained in <code class="code">GAPInfo.UserGapRoot</code>. This directory can be used to tell <strong class="pkg">GAP</strong> about personal preferences, to load some additional code, to install additional packages, or to overwrite some <strong class="pkg">GAP</strong> files, see <a href="../../doc/ref/chap9.html#X7A4973627A5DB27D"><span class="RefLink">Reference: GAP Root Directories</span></a>. Instead of a single <code class="file">.gaprc</code> file we now use more flexible setup based on two files: <code class="file">gap.ini</code> which is read early in the startup process, and <code class="file">gaprc</code> 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 <strong class="pkg">GAP</strong> root directory <code class="code">GAPInfo.UserGapRoot</code> which by default is the first <strong class="pkg">GAP</strong> root directory, see <a href="../../doc/ref/chap3.html#X7FD66F977A3B02DF"><span class="RefLink">Reference: The gap.ini and gaprc files</span></a>. For compatibility, the <code class="file">.gaprc</code> file is still read if the directory <code class="code">GAPInfo.UserGapRoot</code> does not exist. See <a href="../../doc/ref/chap77.html#X7F2FF72A7AD60E0C"><span class="RefLink">Reference: The former .gaprc file</span></a> for the instructions how to migrate your old setup.</p>
<p>Furthermore, there are functions to deal with user preferences, for example, to specify how <strong class="pkg">GAP</strong>'s online help is shown or whether the coloured prompt should be used. Calls to set user preferences may appear in the user's <code class="file">gap.ini</code> file, as explained in <a href="../../doc/ref/chap3.html#X7B0AD104839B6C3C"><span class="RefLink">Reference: Configuring User preferences</span></a>.</p>
<p>In the Windows version, we include a new shell which uses the <strong class="pkg">mintty</strong> terminal in addition to the two previously used shells (Windows command line and <strong class="pkg">RXVT</strong>). The <strong class="pkg">mintty</strong> shell is now recommended. It supports Unicode encoding and has flexible configurations options. Also, <strong class="pkg">GAP</strong> under Windows now starts in the <code class="file">%HOMEDRIVE%%HOMEPATH%</code> 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>
<p>Other changes in the user interface include:</p>
<ul>
<li><p>the command line history is now implemented at the <strong class="pkg">GAP</strong> level, it can be stored on quitting a <strong class="pkg">GAP</strong> session and reread when starting a new session, see <a href="../../doc/ref/chap6.html#X846C3DED84AD7593"><span class="RefLink">Reference: The command line history</span></a>.</p>
</li>
<li><p><code class="code">SetPrintFormattingStatus("stdout",false);</code> may be used to switch off the automatic line breaking in terminal output, see <code class="func">SetPrintFormattingStatus</code> (<a href="../../doc/ref/chap10.html#X8663FCD57E8BC390"><span class="RefLink">Reference: SetPrintFormattingStatus</span></a>).</p>
</li>
<li><p><strong class="pkg">GAP</strong> supports terminals with up to 4096 columns (extendable at compile time).</p>
</li>
<li><p>Directories in <code class="code">-l</code> command-line option can now be specified starting with <code class="code">~/</code>, see <a href="../../doc/ref/chap3.html#X782751D5858A6EAF"><span class="RefLink">Reference: Command Line Options</span></a>.</p>
</li>
<li><p>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 <code class="code">UserPreference("MaxBitsIntView")</code> to see the default value).</p>
</li>
<li><p>The <strong class="pkg">GAP</strong> banner has been made more compact and informative.</p>
</li>
<li><p><code class="func">SetHelpViewer</code> (<a href="../../doc/ref/chap2.html#X87C1BFB2826488B0"><span class="RefLink">Reference: SetHelpViewer</span></a>) now supports the Google Chrome browser.</p>
</li>
<li><p>Multiple matches in the <strong class="pkg">GAP</strong> online help are displayed via a function from the <strong class="pkg">Browse</strong> package, which is loaded in the default configuration. This feature can be replaced by the known pager using the command</p>
<pre class="normal">
SetUserPreference( "browse", "SelectHelpMatches", false );
</pre>
</li>
</ul>
<p><a id="X81318FC0873923C3" name="X81318FC0873923C3"></a></p>
<h5>4.1-4 <span class="Heading">Better documentation</span></h5>
<p>The main <strong class="pkg">GAP</strong> manuals have been converted to the <strong class="pkg">GAPDoc</strong> format provided by the <strong class="pkg">GAPDoc</strong> package by Frank Lübeck and Max Neunhöffer (<span class="URL"><a href="http://www.math.rwth-aachen.de/~Frank.Luebeck/GAPDoc">http://www.math.rwth-aachen.de/~Frank.Luebeck/GAPDoc</a></span>). This documentation format is already used by many packages and is now recommended for all <strong class="pkg">GAP</strong> documentation.</p>
<p>Besides improvements to the documentation layout in all formats (text, PDF and HTML), the new <strong class="pkg">GAP</strong> manuals incorporate a large number of corrections, clarifications, additions and updated examples.</p>
<p>We now provide two HTML versions of the manual, one of them with <strong class="pkg">MathJax</strong> (<span class="URL"><a href="http://www.mathjax.org">http://www.mathjax.org</a></span>) support for better display of mathematical symbols. Also, there are two PDF versions of the manual - a coloured and a monochrome one.</p>
<p>Several separate manuals now became parts of the <strong class="pkg">GAP</strong> Reference manual. Thus, now there are three main <strong class="pkg">GAP</strong> manual books:</p>
<ul>
<li><p><em><strong class="pkg">GAP</strong> Tutorial</em> (see <a href="../../doc/tut/chap1.html#X874E1D45845007FE"><span class="RefLink">Tutorial: Preface</span></a>)</p>
</li>
<li><p><em><strong class="pkg">GAP</strong> Reference manual</em> (see <a href="../../doc/ref/chap1.html#X874E1D45845007FE"><span class="RefLink">Reference: Preface</span></a>)</p>
</li>
<li><p><em><strong class="pkg">GAP</strong> - Changes from Earlier Versions</em> (this manual)</p>
</li>
</ul>
<p>Note that there is no index file combining these three manuals. Instead of that, please use the <strong class="pkg">GAP</strong> help system which will search all of these and about 100 package manuals.</p>
<p><a id="X85D796968453CFBF" name="X85D796968453CFBF"></a></p>
<h4>4.2 <span class="Heading">Packages in <strong class="pkg">GAP</strong> 4.5</span></h4>
<p>Here we list most important changes affecting packages and present new or essentially changed packages. For the changes in the core <strong class="pkg">GAP</strong> system, see Section <a href="chap4.html#X7DA602757C152B0C"><span class="RefLink">4.1</span></a>.</p>
<p><a id="X7E8089C881AB6BA1" name="X7E8089C881AB6BA1"></a></p>
<h5>4.2-1 <span class="Heading">Interface between the core system and packages</span></h5>
<p>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 <strong class="pkg">GAP</strong> 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 <code class="func">LoadPackage</code> (<a href="../../doc/ref/chap76.html#X79B373A77B29D1F5"><span class="RefLink">Reference: LoadPackage</span></a>) and <code class="func">TestPackageAvailability</code> (<a href="../../doc/ref/chap76.html#X8580DF257E4D7046"><span class="RefLink">Reference: TestPackageAvailability</span></a>) 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 <code class="func">IsPackageMarkedForLoading</code> (<a href="../../doc/ref/chap76.html#X8067348B836BAF37"><span class="RefLink">Reference: IsPackageMarkedForLoading</span></a>). 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 <code class="func">DisplayPackageLoadingLog</code> (<a href="../../doc/ref/chap76.html#X7D162DDF813D2BBA"><span class="RefLink">Reference: DisplayPackageLoadingLog</span></a>) and the rest of the Chapter <a href="../../doc/ref/chap76.html#X7B6CD527825945CD"><span class="RefLink">Reference: Using GAP Packages</span></a> which documents how to <em>use</em> <strong class="pkg">GAP</strong> packages), and package authors are very much encouraged to use these logging facilities.</p>
<p>In <strong class="pkg">GAP</strong> 4.4 certain packages were marked as <em>autoloaded</em> and would be loaded, if present, when <strong class="pkg">GAP</strong> started up. In <strong class="pkg">GAP</strong> 4.5, this notion is divided into three. Certain packages are recorded as <em>needed</em> by the <strong class="pkg">GAP</strong> system and others as <em>suggested</em>, in the same way that packages may <em>need</em> or <em>suggest</em> other packages. If a needed package is not loadable, <strong class="pkg">GAP</strong> will not start. Currently only <strong class="pkg">GAPDoc</strong> 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 <strong class="pkg">GAP</strong>. 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 <strong class="pkg">GAP</strong> 4.4.12, see <code class="func">ShowUserPreferences</code> (<a href="../../doc/ref/chap3.html#X7B0AD104839B6C3C"><span class="RefLink">Reference: ShowUserPreferences</span></a>).</p>
<p><strong class="pkg">GAP</strong> packages may now use local <em>namespaces</em> to avoid name clashes for global variables introduced in other packages or in the <strong class="pkg">GAP</strong> library, see <a href="../../doc/ref/chap4.html#X875BA7C58175DEFB"><span class="RefLink">Reference: Namespaces for GAP packages</span></a>.</p>
<p>All guidance on how to <em>develop</em> a <strong class="pkg">GAP</strong> package has been consolidated in the <strong class="pkg">Example</strong> package which also contains a checklist for upgrading a <strong class="pkg">GAP</strong> package to <strong class="pkg">GAP</strong> 4.5, see <span class="RefLink">???</span>.</p>
<p><a id="X81A313117C30EC28" name="X81A313117C30EC28"></a></p>
<h5>4.2-2 <span class="Heading">New and updated packages since <strong class="pkg">GAP</strong> 4.4.12</span></h5>
<p>At the time of the release of <strong class="pkg">GAP</strong> 4.4.12 there were 75 packages redistributed with <strong class="pkg">GAP</strong> (including the <strong class="pkg">TomLib</strong> which was distributed in the core <strong class="pkg">GAP</strong> archive). The first public release of <strong class="pkg">GAP</strong> 4.5 contains precisely 99 packages.</p>
<p>The new packages that have been added to the redistribution since the release of <strong class="pkg">GAP</strong> 4.4.12 are:</p>
<ul>
<li><p><strong class="pkg">Citrus</strong> package by J.D. Mitchell for computations with transformation semigroups and monoids (this package is a replacement of the <strong class="pkg">Monoid</strong> package).</p>
</li>
<li><p><strong class="pkg">cvec</strong> package by M. Neunhöffer, providing an implementation of compact vectors over finite fields.</p>
</li>
<li><p><strong class="pkg">fwtree</strong> package by B. Eick and T. Rossmann for computing trees related to some pro-<span class="SimpleMath">p</span>-groups of finite width.</p>
</li>
<li><p><strong class="pkg">GBNP</strong> package by A.M. Cohen and J.W. Knopper, providing algorithms for computing Grobner bases of noncommutative polynomials over fields with respect to the "total degree first then lexicographical" ordering.</p>
</li>
<li><p><strong class="pkg">genss</strong> 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.</p>
</li>
<li><p><strong class="pkg">HAPprime</strong> package by P. Smith, extending the <strong class="pkg">HAP</strong> package with an implementation of memory-efficient algorithms for the calculation of resolutions of small prime-power groups.</p>
</li>
<li><p><strong class="pkg">hecke</strong> package by D. Traytel, providing functions for calculating decomposition matrices of Hecke algebras of the symmetric groups and <span class="SimpleMath">q</span>-Schur algebras (this package is a port of the <strong class="pkg">GAP</strong> 3 package <strong class="pkg">Specht 2.4</strong> to <strong class="pkg">GAP</strong> 4).</p>
</li>
<li><p><strong class="pkg">Homalg</strong> project by M. Barakat, S. Gutsche, M. Lange-Hegermann et al., containing the following packages for the homological algebra: <strong class="pkg">homalg</strong>, <strong class="pkg">ExamplesForHomalg</strong>, <strong class="pkg">Gauss</strong>, <strong class="pkg">GaussForHomalg</strong>, <strong class="pkg">GradedModules</strong>, <strong class="pkg">GradedRingForHomalg</strong>, <strong class="pkg">HomalgToCAS</strong>, <strong class="pkg">IO_ForHomalg</strong>, <strong class="pkg">LocalizeRingForHomalg</strong>, <strong class="pkg">MatricesForHomalg</strong>, <strong class="pkg">Modules</strong>, <strong class="pkg">RingsForHomalg</strong> and <strong class="pkg">SCO</strong> (see <span class="URL"><a href="http://homalg.math.rwth-aachen.de/">http://homalg.math.rwth-aachen.de/</a></span>).</p>
</li>
<li><p><strong class="pkg">MapClass</strong> package by A. James, K. Magaard and S. Shpectorov to calculate the mapping class group orbits for a given finite group.</p>
</li>
<li><p><strong class="pkg">recogbase</strong> 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).</p>
</li>
<li><p><strong class="pkg">recog</strong> 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 <strong class="pkg">recogbase</strong> package and provides a collection of methods for the constructive recognition of groups (mostly intended for permutation groups, matrix groups and projective groups).</p>
</li>
<li><p><strong class="pkg">SCSCP</strong> package by A. Konovalov and S. Linton, implementing the Symbolic Computation Software Composability Protocol (<strong class="pkg">SCSCP</strong>, see <span class="URL"><a href="http://www.symbolic-computation.org/scscp">http://www.symbolic-computation.org/scscp</a></span>) for <strong class="pkg">GAP</strong>, which provides interfaces to link a <strong class="pkg">GAP</strong> instance with another copy of <strong class="pkg">GAP</strong> or other <strong class="pkg">SCSCP</strong>-compliant system running locally or remotely.</p>
</li>
<li><p><strong class="pkg">simpcomp</strong> package by F. Effenberger and J. Spreer for working with simplicial complexes.</p>
</li>
<li><p><strong class="pkg">Smallsemi</strong> 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.</p>
</li>
<li><p><strong class="pkg">SymbCompCC</strong> package by D. Feichtenschlager for computations with parametrised presentations for finite <span class="SimpleMath">p</span>-groups of fixed coclass.</p>
</li>
</ul>
<p>Furthermore, some packages have been upgraded substantially since the <strong class="pkg">GAP</strong> 4.4.12 release:</p>
<ul>
<li><p><strong class="pkg">Alnuth</strong> 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.</p>
</li>
<li><p><strong class="pkg">CTblLib</strong> package (the <strong class="pkg">GAP</strong> 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 <strong class="pkg">GAP</strong>'s group libraries, better search facilities, and interactive overviews. For details, see the package manual.</p>
</li>
<li><p><strong class="pkg">DESIGN</strong> package by L.H. Soicher:</p>
<ul>
<li><p>The functions <code class="code">PointBlockIncidenceMatrix</code>, <code class="code">ConcurrenceMatrix</code>, and <code class="code">InformationMatrix</code> compute matrices associated with block designs.</p>
</li>
<li><p>The function <code class="code">BlockDesignEfficiency</code> computes certain statistical efficiency measures of a <span class="SimpleMath">1-(v,k,r)</span> design, using exact algebraic computation.</p>
</li>
</ul>
</li>
<li><p><strong class="pkg">Example</strong> package by W. Nickel, G. Gamble and A. Konovalov has a more detailed and up-to-date guidance on developing a <strong class="pkg">GAP</strong> package, see <span class="RefLink">???</span>.</p>
</li>
<li><p><strong class="pkg">FR</strong> package by L. Bartholdi now uses floating-point numbers to compute approximations of rational maps given by their group-theoretical description.</p>
</li>
<li><p>The <strong class="pkg">GAPDoc</strong> package by F. Lübeck and M. Neunhöffer provides various improvements, for example:</p>
<ul>
<li><p>The layout of the text version of the manuals can be configured quite freely, several standard "themes" are provided. The display is now adjusted to the current screen width.</p>
</li>
<li><p>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.</p>
</li>
<li><p>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).</p>
</li>
<li><p>The PDF version of the manuals uses better fonts.</p>
</li>
<li><p>Of course, there are various improvements for authors of manuals as well, for example new functions <code class="func">ExtractExamples</code> (<a href="../../pkg/gapdoc/doc/chap5.html#X8337B2BC79253B3F"><span class="RefLink">GAPDoc: ExtractExamples</span></a>) and <code class="func">RunExamples</code> (<a href="../../pkg/gapdoc/doc/chap5.html#X781D56FC7B938DCB"><span class="RefLink">GAPDoc: RunExamples</span></a>) for automatic testing and correcting of manual examples.</p>
</li>
</ul>
</li>
<li><p><strong class="pkg">Gpd</strong> package by E.J. Moore and C.D. Wensley has been substantially rewritten. The main extensions provide functions for:</p>
<ul>
<li><p>Subgroupoids of a direct product with complete graph groupoid, specified by a root group and choice of rays.</p>
</li>
<li><p>Automorphisms of finite groupoids - by object permutations; by root group automorphisms; and by ray images.</p>
</li>
<li><p>The automorphism group of a finite groupoid together with an isomorphism to a quotient of permutation groups.</p>
</li>
<li><p>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 <strong class="pkg">XMod</strong> package.</p>
</li>
</ul>
</li>
<li><p><strong class="pkg">GRAPE</strong> package by L.H. Soicher:</p>
<ul>
<li><p>With much help from A. Hulpke, the interface between <strong class="pkg">GRAPE</strong> and <code class="file">dreadnaut</code> is now done entirely in <strong class="pkg">GAP</strong> code.</p>
</li>
<li><p>A 32-bit <code class="file">nauty/dreadnaut</code> binary for Windows (XP and later) is included with <strong class="pkg">GRAPE</strong>, so now <strong class="pkg">GRAPE</strong> provides full functionality under Windows, with no installation necessary.</p>
</li>
<li><p>Graphs with ordered partitions of their vertices into "colour-classes" 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).</p>
</li>
<li><p>The <strong class="pkg">GAP</strong> code and old standalone programs for the undocumented functions <code class="code">Enum</code> and <code class="code">EnumColadj</code> have been removed as their functionality can now largely be handled by current documented <strong class="pkg">GAP</strong> and <strong class="pkg">GRAPE</strong> functions.</p>
</li>
</ul>
</li>
<li><p><strong class="pkg">IO</strong> package by M. Neunhöffer:</p>
<ul>
<li><p>New build system to allow for more flexibility regarding the use of compiler options and adjusting to <strong class="pkg">GAP</strong> 4.5.</p>
</li>
<li><p>New functions to access time like <code class="code">IO_gettimeofday</code>, <code class="code">IO_gmtime</code> and <code class="code">IO_localtime</code>.</p>
</li>
<li><p>Some parallel skeletons built on <code class="code">fork</code> like: <code class="code">ParListByFork</code>, <code class="code">ParMapReduceByFork</code>, <code class="code">ParTakeFirstResultByFork</code> and <code class="code">ParWorkerFarmByFork</code>.</p>
</li>
<li><p><code class="code">IOHub</code> objects for automatic I/O multiplexing.</p>
</li>
<li><p>New functions <code class="code">IO_gethostbyname</code> and <code class="code">IO_getsockname</code>.</p>
</li>
</ul>
</li>
<li><p><strong class="pkg">IRREDSOL</strong> package by B. Höfling now covers all irreducible soluble subgroups of <span class="SimpleMath">GL(n,q)</span> for <span class="SimpleMath">q^n < 1000000</span> and primitive soluble permutation groups of degree <span class="SimpleMath">< 1000000</span> (previously, the bound was <span class="SimpleMath">65536</span>). It also has faster group recognition and adds a few omissions for <span class="SimpleMath">GL(3,8)</span> and <span class="SimpleMath">GL(6,5)</span>.</p>
</li>
<li><p><strong class="pkg">ParGAP</strong> 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 <strong class="pkg">MPINU</strong> library which is still supplied with the package (thanks to P. Smith for upgrading <strong class="pkg">ParGAP</strong> build process).</p>
</li>
<li><p><strong class="pkg">OpenMath</strong> 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 <strong class="pkg">SCSCP</strong> package. Also, a third-party external library to support binary OpenMath encoding has been replaced by a proper implementation made entirely in <strong class="pkg">GAP</strong>.</p>
</li>
<li><p><strong class="pkg">Orb</strong> package by J. Müller, M. Neunhöffer and F. Noeske:</p>
<p>There have been numerous improvements to this package:</p>
<ul>
<li><p>A new fast implementation of AVL trees (balanced binary trees) in C.</p>
</li>
<li><p>New interface to hash table functionality and implementation in C for speedup.</p>
</li>
<li><p>Some new hash functions for various object types like transformations.</p>
</li>
<li><p>New function <code class="code">ORB_EstimateOrbitSize</code> using the birthday paradox.</p>
</li>
<li><p>Improved functionality for product replacer objects.</p>
</li>
<li><p>New "tree hash tables".</p>
</li>
<li><p>New functionality to compute weak and strong orbits for semigroups and monoids.</p>
</li>
<li><p><code class="code">OrbitGraph</code> for Orb orbits.</p>
</li>
<li><p>Fast C kernel methods for the following functions:</p>
<p><code class="code">PermLeftQuoTransformationNC</code>, <code class="code">MappingPermSetSet</code>, <code class="code">MappingPermListList</code>, <code class="code">ImageSetOfTransformation</code>, and <code class="code">KernelOfTransformation</code>.</p>
</li>
<li><p>New build system to allow for more flexibility regarding the use of compiler options and to adjust to <strong class="pkg">GAP</strong> 4.5.</p>
</li>
</ul>
</li>
<li><p><strong class="pkg">RCWA</strong> package by S. Kohl among the new features and other improvements has the following:</p>
<ul>
<li><p>A database of all 52394 groups generated by 3 class transpositions of <span class="SimpleMath">ℤ</span> 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 <span class="SimpleMath">ℤ</span> look like.</p>
</li>
<li><p>More routines for investigating the action of an rcwa group on <span class="SimpleMath">ℤ</span>. 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 <span class="SimpleMath">ℤ</span>.</p>
</li>
<li><p>Ability to deal with rcwa permutations of <span class="SimpleMath">ℤ^2</span>.</p>
</li>
<li><p>Important methods have been made more efficient in terms of runtime and memory consumption.</p>
</li>
<li><p>The output has been improved. For example, rcwa permutations are now <code class="code">Display</code>'ed in ASCII text resembling LaTeX output.</p>
</li>
</ul>
</li>
<li><p>The <strong class="pkg">XGAP</strong> 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 <strong class="pkg">XGAP</strong> has been adjusted to <strong class="pkg">GAP</strong> 4.5.</p>
</li>
<li><p>Additionally, some packages with kernel modules or external binaries are now available in Windows. The <code class="file">-win.zip</code> archive and the <strong class="pkg">GAP</strong> installer for Windows include working versions of the following packages: <strong class="pkg">Browse</strong>, <strong class="pkg">cvec</strong>, <strong class="pkg">EDIM</strong>, <strong class="pkg">GRAPE</strong>, <strong class="pkg">IO</strong> and <strong class="pkg">orb</strong>, which were previously unavailable for Windows users.</p>
</li>
</ul>
<p>Finally, the following packages are withdrawn:</p>
<ul>
<li><p><strong class="pkg">IF</strong> 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 <strong class="pkg">SCSCP</strong> package by A. Konovalov and S. Linton.</p>
</li>
<li><p><strong class="pkg">Monoid</strong> package by J. Mitchell is superseded by the <strong class="pkg">Citrus</strong> package by the same author.</p>
</li>
<li><p><strong class="pkg">NQL</strong> package by R. Hartung has been withdrawn by the author.</p>
</li>
</ul>
<p><a id="X83D3FC7781921387" name="X83D3FC7781921387"></a></p>
<h4>4.3 <span class="Heading"><strong class="pkg">GAP</strong> 4.5.5 (July 2012)</span></h4>
<p>Fixed bugs which could lead to crashes:</p>
<ul>
<li><p>For small primes (compact fields) <code class="code">ZmodnZObj(r,p)</code> now returns the corresponding FFE to avoid crashes when compacting matrices. [Reported by Ignat Soroko]</p>
</li>
</ul>
<p>Other fixed bugs:</p>
<ul>
<li><p>Fixed a bug in <code class="func">CommutatorSubgroup</code> (<a href="../../doc/ref/chap39.html#X7A9A3D5578CE33A0"><span class="RefLink">Reference: CommutatorSubgroup</span></a>) for fp groups causing infinite recursion, which could, for example, be triggered by computing automorphism groups.</p>
</li>
<li><p>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]</p>
</li>
<li><p>Computing high powers of matrices ran into an error for matrices in the format of the <strong class="pkg">cvec</strong> package. Now the library function also works with these matrices. [reported by Klaus Lux]</p>
</li>
<li><p>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 <strong class="pkg">ANUPQ</strong> and <strong class="pkg">nq</strong> 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 <strong class="pkg">GAP</strong> to compute more. This also affected other systems, such as OpenBSD, where it now also works correctly.</p>
</li>
<li><p>On Mac OS X, using <strong class="pkg">GAP</strong> 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 "keystroke". 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 <code class="code">rl_event_hook</code> only if <code class="code">OnCharReadHookActive</code> is set.</p>
</li>
<li><p><code class="func">ShowUserPreferences</code> (<a href="../../doc/ref/chap3.html#X7B0AD104839B6C3C"><span class="RefLink">Reference: ShowUserPreferences</span></a>) ran into a break loop in case of several undeclared user preferences. [Reported by James Mitchell]</p>
</li>
<li><p><strong class="pkg">GAP</strong> did not start correctly if the user preference <code class="code">"InfoPackageLoadingLevel"</code> was set to a number <span class="SimpleMath">>= 3</span>. The reason is that <code class="code">PrintFormattedString</code> was called before it was installed. The current fix is a temporary solution.</p>
</li>
<li><p>The <code class="code">"hints"</code> member of <code class="code">TypOutputFile</code> used to contain 3*100 entries, yet <code class="code">addLineBreakHint</code> would write entries with index up to and including 3*99+3=300, leading to a buffer overflow. This would end up overwriting the <code class="code">"stream"</code> member with -1. Fixed by incrementing the size of <code class="code">"hints"</code> to 301. [Reported by Jakob Kroeker]</p>
</li>
<li><p>The function <code class="code">IsDocumentedWord</code> 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.</p>
</li>
<li><p>On Windows, an error occurred if one tried to use the default Windows browser as a help viewer (see <code class="func">SetHelpViewer</code> (<a href="../../doc/ref/chap2.html#X87C1BFB2826488B0"><span class="RefLink">Reference: SetHelpViewer</span></a>)). 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.</p>
</li>
</ul>
<p>Improved functionality:</p>
<ul>
<li><p><code class="func">WriteGapIniFile</code> (<a href="../../doc/ref/chap3.html#X7B0AD104839B6C3C"><span class="RefLink">Reference: WriteGapIniFile</span></a>) on Windows now produces the <code class="file">gap.ini</code> file with Windows style line breaks. Also, an info message is now printed if an existing <code class="file">gap.ini</code> file was moved to a backup file <code class="file">gap.ini.bak</code>.</p>
</li>
<li><p>The <strong class="pkg">CTblLib</strong> and <strong class="pkg">TomLib</strong> packages are removed from the list of suggested packages of the core part of <strong class="pkg">GAP</strong>. Instead they are added to the default list of the user preference <code class="code">"PackagesToLoad"</code>. This way it is possible to configure <strong class="pkg">GAP</strong> to not load these packages via changing the default value of <code class="code">"PackagesToLoad"</code>.</p>
</li>
<li><p>The conjugacy test in <span class="SimpleMath">S_n</span> for intransitive subgroups was improved. This deals with inefficiency issue in the case reported by Stefan Kohl.</p>
</li>
<li><p>Added <code class="code">InstallAndCallPostRestore</code> to <code class="file">lib/system.g</code> and call it in <code class="file">lib/init.g</code> instead of <code class="code">CallAndInstallPostRestore</code> for the function that reads the files listed in <strong class="pkg">GAP</strong> command line. This fixes the problem reported by Yevgen Muntyan when <code class="func">SaveWorkspace</code> (<a href="../../doc/ref/chap3.html#X876544A57C73C488"><span class="RefLink">Reference: SaveWorkspace</span></a>) was used in a file listed in <strong class="pkg">GAP</strong> command line (before, according to the documentation, <code class="func">SaveWorkspace</code> (<a href="../../doc/ref/chap3.html#X876544A57C73C488"><span class="RefLink">Reference: SaveWorkspace</span></a>) was only allowed at the main <strong class="pkg">GAP</strong> prompt).</p>
</li>
<li><p>There is now a new user preference <code class="code">PackagesToIgnore</code>, see <code class="func">SetUserPreference</code> (<a href="../../doc/ref/chap3.html#X7B0AD104839B6C3C"><span class="RefLink">Reference: SetUserPreference</span></a>). 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 <code class="func">LoadPackage</code> (<a href="../../doc/ref/chap76.html#X79B373A77B29D1F5"><span class="RefLink">Reference: LoadPackage</span></a>). This preference is useful for testing purposes if one wants to run some code without loading certain packages.</p>
</li>
</ul>
<p><a id="X79311F9185A267DB" name="X79311F9185A267DB"></a></p>
<h4>4.4 <span class="Heading"><strong class="pkg">GAP</strong> 4.5.6 (September 2012)</span></h4>
<p>Improved functionality:</p>
<ul>
<li><p>The argument of <code class="func">SaveWorkspace</code> (<a href="../../doc/ref/chap3.html#X876544A57C73C488"><span class="RefLink">Reference: SaveWorkspace</span></a>) can now start with <code class="code">~/</code> which is expanded to the users home directory.</p>
</li>
<li><p>Added the method for <code class="func">Iterator</code> (<a href="../../doc/ref/chap30.html#X83ADF8287ED0668E"><span class="RefLink">Reference: Iterator</span></a>) for <code class="func">PositiveIntegers</code> (<a href="../../doc/ref/chap14.html#X7E20D82B79DE5129"><span class="RefLink">Reference: PositiveIntegers</span></a>). [Suggested by Attila Egri-Nagy].</p>
</li>
<li><p>Changed kernel tables such that list access functionality for <code class="code">T_SINGULAR</code> objects can be installed by methods at the <strong class="pkg">GAP</strong> level.</p>
</li>
<li><p>In case of saved history, "UP" arrow after starting <strong class="pkg">GAP</strong> yields last stored line. The user preference <code class="code">HistoryMaxLines</code> is now used when storing and saving history (see <code class="func">SetUserPreference</code> (<a href="../../doc/ref/chap3.html#X7B0AD104839B6C3C"><span class="RefLink">Reference: SetUserPreference</span></a>)).</p>
</li>
</ul>
<p>Fixed bugs which could lead to crashes:</p>
<ul>
<li><p>A crash occuring during garbage collection following a call to <code class="code">AClosVec</code> for a <code class="code">GF(2)</code> code. [Reported by Volker Braun]</p>
</li>
<li><p>A crash when parsing certain syntactically invalid code. [Reported by multiple users]</p>
</li>
<li><p>Fixed and improved command line editing without readline support. Fixed a segfault which could be triggered by a combination of "UP" and "DOWN" arrows. [Reported by James Mitchell]</p>
</li>
<li><p>Fixed a bug in the kernel code for floats that caused a crash on SPARC Solaris in 32-bit mode. [Reported by Volker Braun]</p>
</li>
</ul>
<p>Other fixed bugs:</p>
<ul>
<li><p>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]</p>
</li>
<li><p>An old variable was used in assertion, causing errors in a debugging compilation. [Reported by Volker Braun]</p>
</li>
<li><p>The environment variable <code class="code">PAGER</code> is now correctly interpreted when it contains the full path to the pager program. Furthermore, if the external pager <code class="code">less</code> is found from the environment it is made sure that the option <code class="code">-r</code> is used (same for <code class="code">more -f</code>). [Reported by Benjamin Lorenz]</p>
</li>
<li><p>Fixed a bug in <code class="code">PermliftSeries</code>. [Reported by Aiichi Yamasaki]</p>
</li>
<li><p>Fixed discarder function in lattice computation to distinguish general and zuppo discarder. [Reported by Leonard Soicher]</p>
</li>
<li><p>The <code class="func">GL</code> (<a href="../../doc/ref/chap50.html#X85D607DD82AF3E27"><span class="RefLink">Reference: GL (for dimension and a ring)</span></a>) and <code class="func">SL</code> (<a href="../../doc/ref/chap50.html#X7CA3F7BF83992C6B"><span class="RefLink">Reference: SL (for dimension and a ring)</span></a>) constructors did not correctly handle <code class="code">GL(filter,dim,ring)</code>.</p>
</li>
<li><p>The names of two primitive groups of degree 64 were incorrect.</p>
</li>
<li><p>The <code class="func">\in</code> (<a href="../../doc/ref/chap30.html#X82D39CF980FDBFFA"><span class="RefLink">Reference: \in operation for testing membership</span></a>) 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 <code class="code">SeedFaithfulAction</code> to influence how <code class="func">NiceMonomorphism</code> (<a href="../../doc/ref/chap40.html#X7965086E82ABCF41"><span class="RefLink">Reference: NiceMonomorphism</span></a>) builds the nice monomorphims for a matrix groups.</p>
</li>
<li><p>Wrong <code class="func">PrintObj</code> (<a href="../../doc/ref/chap6.html#X815BF22186FD43C9"><span class="RefLink">Reference: PrintObj</span></a>) method was removed to fix delegations accordingly to <a href="../../doc/ref/chap6.html#X8074A8387C9DB9A8"><span class="RefLink">Reference: View and Print</span></a>.</p>
</li>
<li><p>Fixed a method for <code class="func">Coefficients</code> (<a href="../../doc/ref/chap61.html#X80B32F667BF6AFD8"><span class="RefLink">Reference: Coefficients</span></a>) 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]</p>
</li>
</ul>
<p>Improved documentation:</p>
<ul>
<li><p>Removed outdated statements from the documentation of <code class="func">StructureDescription</code> (<a href="../../doc/ref/chap39.html#X8199B74B84446971"><span class="RefLink">Reference: StructureDescription</span></a>) which now non-ambiguosly states that <code class="code">StructureDescription</code> 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.</p>
</li>
<li><p><strong class="pkg">GAP</strong> 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 <strong class="pkg">GAP</strong> is started with a root path that contains a newer version. [Reported by Sebastian Gutsche]</p>
</li>
<li><p>Provided a better description of user preferences mechanism (<a href="../../doc/ref/chap3.html#X7B0AD104839B6C3C"><span class="RefLink">Reference: Configuring User preferences</span></a>) and a hint to familiarise with them using <code class="func">WriteGapIniFile</code> (<a href="../../doc/ref/chap3.html#X7B0AD104839B6C3C"><span class="RefLink">Reference: WriteGapIniFile</span></a>) 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 <strong class="pkg">GAP</strong> sessions.</p>
</li>
</ul>
<p>New packages added for the redistribution with <strong class="pkg">GAP</strong>:</p>
<ul>
<li><p><strong class="pkg">AutoDoc</strong> package by S. Gutsche, providing tools for automated generation of <strong class="pkg">GAPDoc</strong> manuals.</p>
</li>
<li><p><strong class="pkg">Convex</strong> package by S. Gutsche, which provides structures and algorithms for convex geometry.</p>
</li>
<li><p><strong class="pkg">PolymakeInterface</strong> package by T. Baechler and S. Gutsche, providing a link to the callable library of the <strong class="pkg">polymake</strong> system (<span class="URL"><a href="http://www.polymake.org">http://www.polymake.org</a></span>).</p>
</li>
<li><p><strong class="pkg">ToolsForHomalg</strong> package by M. Barakat, S. Gutsche and M. Lange-Hegermann, which provides some auxiliary functionality for the <strong class="pkg">homalg</strong> project (<span class="URL"><a href="http://homalg.math.rwth-aachen.de/">http://homalg.math.rwth-aachen.de/</a></span>).</p>
</li>
</ul>
<p><a id="X81528B5F78B996D2" name="X81528B5F78B996D2"></a></p>
<h4>4.5 <span class="Heading"><strong class="pkg">GAP</strong> 4.5.7 (December 2012)</span></h4>
<p>Fixed bugs which could lead to crashes:</p>
<ul>
<li><p>Closing with <code class="code">LogInputTo</code> (or <code class="code">LogOutputTo</code>) a logfile opened with <code class="func">LogTo</code> (<a href="../../doc/ref/chap9.html#X79813A6686894960"><span class="RefLink">Reference: LogTo</span></a>) left the data structures corrupted, resulting in a crash.</p>
</li>
<li><p>On 32-bit systems we can have long integers <code class="code">n</code> such that <code class="code">Log2Int(n)</code> is not an immediate integer. In such cases <code class="code">Log2Int</code> gave wrong or corrupted results which in turn could crash <strong class="pkg">GAP</strong>, e.g., in <code class="code">ViewObj(n)</code>.</p>
</li>
<li><p>Some patterns of use of <code class="func">UpEnv</code> (<a href="../../doc/ref/chap6.html#X79E66DA2875303B0"><span class="RefLink">Reference: UpEnv</span></a>) and <code class="func">DownEnv</code> (<a href="../../doc/ref/chap6.html#X79E66DA2875303B0"><span class="RefLink">Reference: DownEnv</span></a>) were leading to a segfault.</p>
</li>
</ul>
<p>Other fixed bugs:</p>
<ul>
<li><p>Viewing of long negative integers was broken, because it went into a break loop.</p>
</li>
<li><p>Division by zero in <code class="func">ZmodnZ</code> (<a href="../../doc/ref/chap14.html#X79CE76AD82B3E2B2"><span class="RefLink">Reference: ZmodnZ</span></a>) (<span class="SimpleMath">n</span> not prime) produced invalid objects. [Reported by Mark Dickinson]</p>
</li>
<li><p>Fixed a bug in determining multiplicative inverse for a zero polynomial.</p>
</li>
<li><p>Fixed a bug causing infinite recursion in <code class="func">NaturalHomomorphismByNormalSubgroup</code> (<a href="../../doc/ref/chap39.html#X80FC390C7F38A13F"><span class="RefLink">Reference: NaturalHomomorphismByNormalSubgroup</span></a>).</p>
</li>
<li><p>A workaround was added to deal with a package method creating pcgs for permutation groups for which the entry <code class="code">permpcgsNormalSteps</code> is missing.</p>
</li>
<li><p>For a semigroup of associative words that is not the full semigroup of all associative words, the methods for <code class="func">Size</code> (<a href="../../doc/ref/chap30.html#X858ADA3B7A684421"><span class="RefLink">Reference: Size</span></a>) and <code class="func">IsTrivial</code> (<a href="../../doc/ref/chap30.html#X7E3402D6799D3C24"><span class="RefLink">Reference: IsTrivial</span></a>) called one another causing infinite recursion.</p>
</li>
<li><p>The 64-bit version of the <code class="file">gac</code> script produced wrong (>= 2^31) CRC values because of an integer conversion problem.</p>
</li>
<li><p>It was not possible to compile <strong class="pkg">GAP</strong> on some systems where <code class="code">HAVE_SELECT</code> detects as false.</p>
</li>
<li><p>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]</p>
</li>
</ul>
<p>New packages added for the redistribution with <strong class="pkg">GAP</strong>:</p>
<ul>
<li><p><strong class="pkg">Float</strong> package by L. Bartholdi, which extends <strong class="pkg">GAP</strong> 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.</p>
</li>
<li><p><strong class="pkg">ToricVarieties</strong> package by S. Gutsche, which provides data structures to handle toric varieties by their commutative algebra structure and by their combinatorics.</p>
</li>
</ul>
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