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<div class="ChapSects"><a href="chap3.html#X8175857F79C8AD8E">3 <span class="Heading">Changes between <strong class="pkg">GAP</strong> 4.5 and <strong class="pkg">GAP</strong> 4.6</span></a>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap3.html#X837BB2577D478E55">3.1 <span class="Heading"><strong class="pkg">GAP</strong> 4.6.2 (February 2013)</span></a>
</span>
<div class="ContSSBlock">
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap3.html#X8436976E7E7ED84B">3.1-1 <span class="Heading">Changes in the core <strong class="pkg">GAP</strong> system introduced in <strong class="pkg">GAP</strong> 4.6</span></a>
</span>
<span class="ContSS"><br /><span class="nocss"> </span><a href="chap3.html#X79A4DFE97A230E6D">3.1-2 <span class="Heading">New and updated packages since <strong class="pkg">GAP</strong> 4.5.4</span></a>
</span>
</div></div>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap3.html#X7C2A78667F08A971">3.2 <span class="Heading"><strong class="pkg">GAP</strong> 4.6.3 (March 2013)</span></a>
</span>
</div>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap3.html#X82859C4083F0D7B9">3.3 <span class="Heading"><strong class="pkg">GAP</strong> 4.6.4 (April 2013)</span></a>
</span>
</div>
<div class="ContSect"><span class="tocline"><span class="nocss"> </span><a href="chap3.html#X7F7F29B27BF76872">3.4 <span class="Heading"><strong class="pkg">GAP</strong> 4.6.5 (July 2013)</span></a>
</span>
</div>
</div>
<h3>3 <span class="Heading">Changes between <strong class="pkg">GAP</strong> 4.5 and <strong class="pkg">GAP</strong> 4.6</span></h3>
<p>This chapter lists most important changes between <strong class="pkg">GAP</strong> 4.5.7 and <strong class="pkg">GAP</strong> 4.6.2 (i.e. between the last release of <strong class="pkg">GAP</strong> 4.5 and the first public release of <strong class="pkg">GAP</strong> 4.6). It also contains information about subsequent update releases for <strong class="pkg">GAP</strong> 4.6.</p>
<p><a id="X837BB2577D478E55" name="X837BB2577D478E55"></a></p>
<h4>3.1 <span class="Heading"><strong class="pkg">GAP</strong> 4.6.2 (February 2013)</span></h4>
<p><a id="X8436976E7E7ED84B" name="X8436976E7E7ED84B"></a></p>
<h5>3.1-1 <span class="Heading">Changes in the core <strong class="pkg">GAP</strong> system introduced in <strong class="pkg">GAP</strong> 4.6</span></h5>
<p>Improved and extended functionality:</p>
<ul>
<li><p>It is now possible to declare a name as an operation with two or more arguments (possibly several times) and <em>THEN</em> declare it as an attribute. Previously this was only possible in the other order. This should make the system more independent of the order in which packages are loaded.</p>
</li>
<li><p>Words in fp groups are now printed in factorised form if possible and not too time-consuming, i.e. <code class="code">a*b*a*b*a*b</code> will be printed as <code class="code">(a*b)^3</code>.</p>
</li>
<li><p>Added methods to calculate Hall subgroups in nonsolvable groups.</p>
</li>
<li><p>Added a generic method for <code class="func">IsPSolvable</code> (<a href="../../doc/ref/chap39.html#X81130F9A7CFCF6BF"><span class="RefLink">Reference: IsPSolvable</span></a>) and a better generic method for <code class="func">IsPNilpotent</code> (<a href="../../doc/ref/chap39.html#X87415A8485FCF510"><span class="RefLink">Reference: IsPNilpotent</span></a>) for groups.</p>
</li>
<li><p>Improvements to action homomorphisms: image of an element can use existing stabiliser chain of the image group (to reduce the number of images to compute), preimages under linear/projective action homomorphisms use linear algebra to avoid factorisation.</p>
</li>
<li><p>To improve efficiency, additional code was added to make sure that the <code class="code">HomePcgs</code> of a permutation group is in <code class="code">IsPcgsPermGroupRep</code> representation in more cases.</p>
</li>
<li><p>Added an operation <code class="func">SortBy</code> (<a href="../../doc/ref/chap21.html#X7FE4975F8166884D"><span class="RefLink">Reference: SortBy</span></a>) with arguments being a function <var class="Arg">f</var> of one argument and a list <var class="Arg">l</var> to be sorted in such a way that <code class="code"><var class="Arg">l</var>(<var class="Arg">f</var>[i]) <= <var class="Arg">l</var>(<var class="Arg">f</var>[i+1])</code>.</p>
</li>
<li><p>Added a kernel function <code class="code">MEET_BLIST</code> which returns <code class="keyw">true</code> if the two boolean lists have <code class="keyw">true</code> in any common position and <code class="keyw">false</code> otherwise. This is useful for representing subsets of a fixed set by boolean lists.</p>
</li>
<li><p>When assigning to a position in a compressed FFE vector <strong class="pkg">GAP</strong> now checks to see if the value being assigned can be converted into an internal FFE element if it isn't one already. This uses new attribute <code class="func">AsInternalFFE</code> (<a href="../../doc/ref/chap59.html#X807959EE82CED148"><span class="RefLink">Reference: AsInternalFFE</span></a>), for which methods are installed for internal FFEs, Conway FFEs and ZmodpZ objects.</p>
</li>
<li><p>Replaced <code class="func">ViewObj</code> (<a href="../../doc/ref/chap6.html#X815BF22186FD43C9"><span class="RefLink">Reference: ViewObj</span></a>) method for fields by <code class="func">ViewString</code> (<a href="../../doc/ref/chap27.html#X7803FBCA79DB5529"><span class="RefLink">Reference: ViewString</span></a>) method to improve the way how polynomial rings over algebraic extenstions of fields are displayed.</p>
</li>
<li><p>Made the info string (optional 2nd argument to <code class="func">InstallImmediateMethod</code> (<a href="../../doc/ref/chap78.html#X87B47AC0849611F8"><span class="RefLink">Reference: InstallImmediateMethod</span></a>)) behave similarly to the info string in <code class="func">InstallMethod</code> (<a href="../../doc/ref/chap78.html#X837EFDAB7BEF290B"><span class="RefLink">Reference: InstallMethod</span></a>). In particular, <code class="func">TraceImmediateMethods</code> (<a href="../../doc/ref/chap7.html#X81078D3387A38E31"><span class="RefLink">Reference: TraceImmediateMethods</span></a>) now always prints the name of the operation.</p>
</li>
<li><p>Syntax errors such as <code class="code">Unbind(x,1)</code> had the unhelpful property that <code class="code">x</code> got unbound before the syntax error was reported. A specific check was added to catch this and similar cases a little earlier.</p>
</li>
<li><p>Allow a <code class="code">GAPARGS</code> parameter to the top-level <strong class="pkg">GAP</strong> <code class="file">Makefile</code> to pass extra arguments to the <strong class="pkg">GAP</strong> used for manual building.</p>
</li>
<li><p>Added an attribute <code class="func">UnderlyingRingElement</code> (<a href="../../doc/ref/chap64.html#X874B2B2A7F5A9A78"><span class="RefLink">Reference: UnderlyingRingElement</span></a>) for Lie objects.</p>
</li>
<li><p>The function <code class="func">PrimeDivisors</code> (<a href="../../doc/ref/chap14.html#X80E7A5D381C64CC9"><span class="RefLink">Reference: PrimeDivisors</span></a>) now became an attribute. [suggested by Mohamed Barakat]</p>
</li>
<li><p>Added an operation <code class="func">DistancePerms</code> (<a href="../../doc/ref/chap42.html#X7BC944F57A04AFF2"><span class="RefLink">Reference: DistancePerms</span></a>) with a kernel method for internal permutations and a generic method.</p>
</li>
<li><p>Added a method for <code class="func">Subfields</code> (<a href="../../doc/ref/chap58.html#X83490C65819D85FE"><span class="RefLink">Reference: Subfields</span></a>) to support large finite fields. [reported by Inneke van Gelder]</p>
</li>
</ul>
<p>Fixed bugs which could lead to crashes:</p>
<ul>
<li><p>The extremely old <code class="code">DEBUG_DEADSONS_BAGS</code> compile-time option has not worked correctly for many years and indeed crashes <strong class="pkg">GAP</strong>. The type of bug it is there to detect has not arisen in many years and we have certainly not used this option, so it has been removed. [Reported by Volker Braun]</p>
</li>
</ul>
<p>Other fixed bugs:</p>
<ul>
<li><p>Scanning of floating point literals collided with iterated use of integers as record field elements in expressions like <code class="code">r.1.2</code>.</p>
</li>
<li><p>Fixed two potential problems in <code class="code">NorSerPermPcgs</code>, one corrupting some internal data and one possibly mixing up different pcgs.</p>
</li>
<li><p>Fixed a performance problem with <code class="func">NiceMonomorphism</code> (<a href="../../doc/ref/chap40.html#X7965086E82ABCF41"><span class="RefLink">Reference: NiceMonomorphism</span></a>). [reported by John Bamberg]</p>
</li>
<li><p>Fixed a bug in <code class="func">ReadCSV</code> (<a href="../../doc/ref/chap10.html#X86FDC1EF82CAD2DA"><span class="RefLink">Reference: ReadCSV</span></a>) that caused some <code class="file">.csv</code> files being parsed incorrectly.</p>
</li>
</ul>
<p>No longer supported:</p>
<ul>
<li><p>The file <code class="file">lib/consistency.g</code>, which contained three undocumented auxiliary functions, has been removed from the library. In addition, the global record <code class="code">Revision</code> is now deprecated, so there is no need to bind its components in <strong class="pkg">GAP</strong> packages.</p>
</li>
</ul>
<p><a id="X79A4DFE97A230E6D" name="X79A4DFE97A230E6D"></a></p>
<h5>3.1-2 <span class="Heading">New and updated packages since <strong class="pkg">GAP</strong> 4.5.4</span></h5>
<p>At the time of the release of <strong class="pkg">GAP</strong> 4.5 there were 99 packages redistributed with <strong class="pkg">GAP</strong>. The first public release of <strong class="pkg">GAP</strong> 4.6 contains 106 packages.</p>
<p>The new packages that have been added to the redistribution since the release of <strong class="pkg">GAP</strong> 4.5.4 are:</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">Congruence</strong> package by A. Konovalov, which provides functions to construct various canonical congruence subgroups in <span class="SimpleMath">SL_2(ℤ)</span>, and also intersections of a finite number of such subgroups, implements the algorithm for generating Farey symbols for congruence subgroups and uses it to produce a system of independent generators for these subgroups.</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">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">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>
<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>
<p>Furthermore, some packages have been upgraded substantially since the <strong class="pkg">GAP</strong> 4.5.4 release:</p>
<ul>
<li><p>Starting from 2.x.x, the functionality for iterated monodromy groups has been moved from the <strong class="pkg">FR</strong> package by L. Bartholdi to a separate package IMG (currently undeposited, available from <span class="URL"><a href="https://github.com/laurentbartholdi/img">https://github.com/laurentbartholdi/img</a></span>). This completely removes the dependency of <strong class="pkg">FR</strong> on external library modules, and should make its installation much easier.</p>
</li>
</ul>
<p><a id="X7C2A78667F08A971" name="X7C2A78667F08A971"></a></p>
<h4>3.2 <span class="Heading"><strong class="pkg">GAP</strong> 4.6.3 (March 2013)</span></h4>
<p>Improved functionality:</p>
<ul>
<li><p>Several changes were made to <code class="func">IdentityMat</code> (<a href="../../doc/ref/chap24.html#X7DB902CE848D1524"><span class="RefLink">Reference: IdentityMat</span></a>) and <code class="func">NullMat</code> (<a href="../../doc/ref/chap24.html#X86D343A77D9B3D4D"><span class="RefLink">Reference: NullMat</span></a>). First off, the documentation was changed to properly state that these functions support arbitrary rings, and not just fields. Also, more usage examples were added to the manual.</p>
<p>For <code class="code">NullMat</code>, it is now also always possible to specify a ring element instead of a ring, and this is documented. This matches existing <code class="code">IdentityMat</code> behavior, and partially worked before (undocumented), but in some cases could run into error or infinite recursion.</p>
<p>In the other direction, if a finite field element, <code class="code">IdentityMat</code> now really creates a matrix over the smallest field containing that element. Previously, a matrix over the prime field was created instead, contrary to the documentation.</p>
<p>Furthermore, <code class="code">IdentityMat</code> over small finite fields is now substantially faster when creating matrices of large dimension (say a thousand or so).</p>
<p>Finally, <code class="func">MutableIdentityMat</code> (<a href="../../doc/ref/chap77.html#X7F6A6CBC7C9E91E5"><span class="RefLink">Reference: MutableIdentityMat</span></a>) and <code class="func">MutableNullMat</code> (<a href="../../doc/ref/chap77.html#X7F6A6CBC7C9E91E5"><span class="RefLink">Reference: MutableNullMat</span></a>) were explicitly declared obsolete (and may be removed in <strong class="pkg">GAP</strong> 4.7). They actually were deprecated since <strong class="pkg">GAP</strong> 4.1, and their use discouraged by the manual. Code using them should switch to <code class="func">IdentityMat</code> (<a href="../../doc/ref/chap24.html#X7DB902CE848D1524"><span class="RefLink">Reference: IdentityMat</span></a>) respectively <code class="func">NullMat</code> (<a href="../../doc/ref/chap24.html#X86D343A77D9B3D4D"><span class="RefLink">Reference: NullMat</span></a>).</p>
</li>
<li><p>Two new <code class="func">PerfectResiduum</code> (<a href="../../doc/ref/chap39.html#X83D5C8B8865C85F1"><span class="RefLink">Reference: PerfectResiduum</span></a>) methods were added for solvable and perfect groups, handling these cases optimally. Moreover, the existing generic method was improved by changing it to use <code class="func">DerivedSeriesOfGroup</code> (<a href="../../doc/ref/chap39.html#X7A879948834BD889"><span class="RefLink">Reference: DerivedSeriesOfGroup</span></a>). Previously, it would always compute the derived series from scratch and then throw away the result.</p>
</li>
<li><p>A new <code class="func">MinimalGeneratingSet</code> (<a href="../../doc/ref/chap39.html#X81D15723804771E2"><span class="RefLink">Reference: MinimalGeneratingSet</span></a>) method for groups handled by a nice monomorphisms was added, similar to the existing <code class="func">SmallGeneratingSet</code> (<a href="../../doc/ref/chap39.html#X814DBABC878D5232"><span class="RefLink">Reference: SmallGeneratingSet</span></a>) method. This is useful if the nice monomorphism is already mapping into a pc or pcp group.</p>
</li>
<li><p>Added a special method for <code class="func">DerivedSubgroup</code> (<a href="../../doc/ref/chap39.html#X7CC17CF179ED7EF2"><span class="RefLink">Reference: DerivedSubgroup</span></a>) if the group is known to be abelian.</p>
</li>
</ul>
<p>Fixed bugs:</p>
<ul>
<li><p>Fixed a bug in <code class="func">PowerModInt</code> (<a href="../../doc/ref/chap14.html#X7E404B1183DBC82A"><span class="RefLink">Reference: PowerModInt</span></a>) computing <span class="SimpleMath">r^e</span> mod <span class="SimpleMath">m</span> in a special case when <span class="SimpleMath">e=0</span> and <span class="SimpleMath">m=0</span>. [Reported by Ignat Soroko]</p>
</li>
<li><p><code class="func">CoefficientsQadic</code> (<a href="../../doc/ref/chap14.html#X79B466E984CD52D4"><span class="RefLink">Reference: CoefficientsQadic</span></a>) now better checks its arguments to avoid an infinite loop when being asked for a <var class="Arg">q</var>-adic representation for <span class="SimpleMath">q=1</span>. [Reported by Ignat Soroko]</p>
</li>
<li><p>Methods for <code class="code">SylowSubgroupOp</code> (see <code class="func">SylowSubgroup</code> (<a href="../../doc/ref/chap39.html#X7AA351308787544C"><span class="RefLink">Reference: SylowSubgroup</span></a>)) for symmetric and alternating group did not always set <code class="func">IsPGroup</code> (<a href="../../doc/ref/chap39.html#X8089F18C810B7E3E"><span class="RefLink">Reference: IsPGroup</span></a>) and <code class="func">PrimePGroup</code> (<a href="../../doc/ref/chap39.html#X87356BAA7E9E2142"><span class="RefLink">Reference: PrimePGroup</span></a>) for the returned Sylow subgroup.</p>
</li>
<li><p>Display of matrices consisting of Conway field elements (which are displayed as polynomials) did not print constant 1 terms.</p>
</li>
<li><p>Added an extra check and a better error message in the method to access <em>natural</em> generators of domains using the <code class="code">.</code> operator (see <code class="func">GeneratorsOfDomain</code> (<a href="../../doc/ref/chap31.html#X7E353DD1838AB223"><span class="RefLink">Reference: GeneratorsOfDomain</span></a>)).</p>
</li>
<li><p>Trying to solve the word problem in an fp group where one or more generators has a name of more than one alphabetic character led to a break loop.</p>
</li>
<li><p>Provided the default method for <code class="func">AbsoluteIrreducibleModules</code> (<a href="../../doc/ref/chap71.html#X7D0BD5337D1C069B"><span class="RefLink">Reference: AbsoluteIrreducibleModules</span></a>) as a temporary workaround for the problem which may cause returning wrong results or producing an error when being called for a non-prime field.</p>
</li>
<li><p>A bug in the <strong class="pkg">GAP</strong> kernel caused <code class="code">RNamObj</code> to error out when called with a string that had the <code class="func">IsSSortedList</code> (<a href="../../doc/ref/chap21.html#X80CDAF45782E8DCB"><span class="RefLink">Reference: IsSSortedList</span></a>) property set (regardless of whether it was set to <code class="keyw">true</code> or <code class="keyw">false</code>). This in turn would lead to strange (and inappropriate) errors when using such a string to access entries of a record.</p>
</li>
<li><p><strong class="pkg">GAP</strong> can store vectors over small finite fields (size at most 256) in a special internal data representation where each entry of the vector uses exactly one byte. Due to an off-by-one bug, the case of a field with exactly 256 elements was not handled properly. As a result, <strong class="pkg">GAP</strong> failed to convert a vector to the special data representation, which in some situations could lead to a crash. The off-by-one error was fixed and now vectors over <span class="SimpleMath">GF(256)</span> work as expected.</p>
</li>
<li><p>A bug in the code for accessing sublist via the <code class="code">list{poss}</code> syntax could lead to <strong class="pkg">GAP</strong> crashing. Specifically, if the list was a compressed vector over a finite field, and the sublist syntax was nested, as in <code class="code">vec{poss1}{poss2}</code>. This now correctly triggers an error instead of crashing.</p>
</li>
</ul>
<p>New packages added for the redistribution with <strong class="pkg">GAP</strong>:</p>
<ul>
<li><p><strong class="pkg">SpinSym</strong> package by L. Maas, which contains Brauer tables of Schur covers of symmetric and alternating groups and provides some related functionalities.</p>
</li>
</ul>
<p><a id="X82859C4083F0D7B9" name="X82859C4083F0D7B9"></a></p>
<h4>3.3 <span class="Heading"><strong class="pkg">GAP</strong> 4.6.4 (April 2013)</span></h4>
<p>New functionality:</p>
<ul>
<li><p>New command line option <code class="code">-O</code> was introduced to disable loading obsolete variables. This option may be used, for example, to check that they are not used in a <strong class="pkg">GAP</strong> package or one's own <strong class="pkg">GAP</strong> code. For further details see <a href="../../doc/ref/chap3.html#X79CCD3A6821E5A37"><span class="RefLink">Reference: options</span></a> and <a href="../../doc/ref/chap77.html#X78C85ED17F00DCC1"><span class="RefLink">Reference: Replaced and Removed Command Names</span></a>.</p>
</li>
</ul>
<p>Fixed bugs which could lead to incorrect results:</p>
<ul>
<li><p>Fixed the bug in <code class="func">NewmanInfinityCriterion</code> (<a href="../../doc/ref/chap47.html#X85C9FD548394C1E2"><span class="RefLink">Reference: NewmanInfinityCriterion</span></a>) which may cause returning <code class="keyw">true</code> instead of <code class="keyw">false</code>. [Reported by Lev Glebsky]</p>
</li>
</ul>
<p>Fixed bugs which could lead to crashes:</p>
<ul>
<li><p>Fixed the kernel method for <code class="func">Remove</code> (<a href="../../doc/ref/chap21.html#X7E98B11B79BA9167"><span class="RefLink">Reference: Remove</span></a>) which did not raise an error in case of empty lists, but corrupted the object. The error message in a library method is also improved. [Reported by Roberto Ràdina]</p>
</li>
</ul>
<p>Fixed bugs that could lead to break loops:</p>
<ul>
<li><p>Fixed requirements in a method to multiply a list and an algebraic element. [Reported by Sebastian Gutsche]</p>
</li>
<li><p>Fixed a bug in <code class="func">NaturalCharacter</code> (<a href="../../doc/ref/chap72.html#X82C01DDB82D751A9"><span class="RefLink">Reference: NaturalCharacter (for a group)</span></a>) entering a break loop when being called on a homomorphism whose image is not a permutation group. [Reported by Sebastian Gutsche]</p>
</li>
<li><p>Fixed a bug in <code class="func">ExponentsConjugateLayer</code> (<a href="../../doc/ref/chap45.html#X868D6DB07D349460"><span class="RefLink">Reference: ExponentsConjugateLayer</span></a>) which occured, for example, in some calls of <code class="func">SubgroupsSolvableGroup</code> (<a href="../../doc/ref/chap39.html#X7AD7804A803910AC"><span class="RefLink">Reference: SubgroupsSolvableGroup</span></a>) [Reported by Ramon Esteban-Romero]</p>
</li>
<li><p>Fixed a problem with displaying function fields, e.g. <code class="code">Field(Indeterminate(Rationals,"x"))</code>. [Reported by Jan Willem Knopper]</p>
</li>
<li><p>Fixed two bugs in the code for <code class="func">NaturalHomomorphismByIdeal</code> (<a href="../../doc/ref/chap56.html#X83D53D98809EC461"><span class="RefLink">Reference: NaturalHomomorphismByIdeal</span></a>) for polynomial rings. [Reported by Martin Leuner]</p>
</li>
<li><p>Added missing method for <code class="func">String</code> (<a href="../../doc/ref/chap27.html#X81FB5BE27903EC32"><span class="RefLink">Reference: String</span></a>) for <code class="code">-infinity</code>.</p>
</li>
<li><p>Fixed the bug with <code class="func">ONanScottType</code> (<a href="../../doc/ref/chap43.html#X7E50211A7B92455F"><span class="RefLink">Reference: ONanScottType</span></a>) not recognising product action properly in some cases.</p>
</li>
<li><p>The method for <code class="func">SlotUsagePattern</code> (<a href="../../doc/ref/chap37.html#X84C83CE98194FD03"><span class="RefLink">Reference: SlotUsagePattern</span></a>) for straight line programs had a bug which triggered an error, if the straight line program contained unnecessary steps.</p>
</li>
</ul>
<p><a id="X7F7F29B27BF76872" name="X7F7F29B27BF76872"></a></p>
<h4>3.4 <span class="Heading"><strong class="pkg">GAP</strong> 4.6.5 (July 2013)</span></h4>
<p>Improved functionality:</p>
<ul>
<li><p><code class="func">TraceMethods</code> (<a href="../../doc/ref/chap7.html#X80B044017C9E4137"><span class="RefLink">Reference: TraceMethods (for operations)</span></a>) and <code class="func">UntraceMethods</code> (<a href="../../doc/ref/chap7.html#X7EB04D387C53E4C1"><span class="RefLink">Reference: UntraceMethods (for operations)</span></a>) now better check their arguments and provide a sensible error message if being called without arguments. Also, both variants of calling them are now documented.</p>
</li>
<li><p>Library methods for <code class="func">Sortex</code> (<a href="../../doc/ref/chap21.html#X87287FCA81E2B06A"><span class="RefLink">Reference: Sortex</span></a>) are now replaced by faster ones using the kernel <code class="func">SortParallel</code> (<a href="../../doc/ref/chap21.html#X791F2B2C7E9B9A46"><span class="RefLink">Reference: SortParallel</span></a>) functionality instead of making expensive zipped lists.</p>
</li>
</ul>
<p>Fixed bugs which could lead to incorrect results:</p>
<ul>
<li><p><code class="func">IntHexString</code> (<a href="../../doc/ref/chap27.html#X7B6D118184F692A0"><span class="RefLink">Reference: IntHexString</span></a>) wrongly produced a large integer when there were too many leading zeros. [Reported by Joe Bohanon]</p>
</li>
</ul>
<p>Fixed bugs that could lead to break loops:</p>
<ul>
<li><p>A bug that may occur in some cases while calling <code class="func">TransitiveIdentification</code> (<a href="../../doc/ref/chap50.html#X7EE614D780C713D1"><span class="RefLink">Reference: TransitiveIdentification</span></a>). [Reported by Izumi Miyamoto]</p>
</li>
<li><p>The new code for semidirect products of permutation groups, introduced in <strong class="pkg">GAP</strong> 4.6, had a bug which was causing problems for <code class="func">Projection</code> (<a href="../../doc/ref/chap32.html#X8769E8DA80BC96C1"><span class="RefLink">Reference: Projection</span></a>). [Reported by Graham Ellis]</p>
</li>
</ul>
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