<Chapter Label="ChangesGAP48toGAP49"> 
<Heading>Changes between &GAP; 4.8 and &GAP; 4.9</Heading>

This chapter contains an overview of the most important changes
introduced in &GAP; 4.9.1 release (the 1st public release of &GAP; 4.9).
Later it will also contain information about subsequent update 
releases for &GAP; 4.9.
<P/>

These changes are also listed on the Wiki page
<URL>https://github.com/gap-system/GAP/wiki/gap-4.9-release-notes</URL>.

<Section Label="GAP491">
<Heading>&GAP; 4.9.1 (May 2018)</Heading>

<Subsection Label="Changes in the core GAP49 system"> 
<Heading>Changes in the core &GAP; system introduced in &GAP; 4.9</Heading>

Major changes:

<List>
<Item>
Merged &HPCGAP; into &GAP;. For details, please refer to Subsection
<Ref Label="HPC-GAP-WIP"/> at the end of these release notes.
</Item>
<Item>
&GAP; has a new build system, which resolves many quirks and issues with the
old system, and will be easier to maintain. For regular users, the usual 
<C>./configure &amp;&amp; make</C> should work fine as before.
If you are interested in technical details on the new build system,
take a look at <File>README.buildsys.md</File>.
</Item>
<Item>
The guidelines for developing &GAP; packages were revised and moved from the
Example package to <Ref BookName="ref" Label="Using and Developing GAP Packages"/>
(<URL><LinkText>&Hash;484</LinkText><Link>https://github.com/gap-system/gap/pull/484</Link></URL>).
</Item>
<Item>
In addition to supporting single argument lambda functions like 
<C>a -> a+1</C>, &GAP; now supports lambdas with fewer or more than
one argument, or even a variable number. E.g. <C>{a,b} -> a+b</C>
is a shorthand for <C>function(a,b) return a+b; end</C>. For details
on how to use this, see <Ref BookName="ref" Sect="Function"/>.
For technical details, e.g. why we did not choose the syntax
<C>(a,b) -> a+b</C>, see
<URL><LinkText>&Hash;490</LinkText><Link>https://github.com/gap-system/gap/pull/490</Link></URL>.
</Item>
<Item>
Function calls, list accesses and records accesses now can be nested.
For example, you can now write <C>y := f().x;</C> (essentially equivalent to
<C>y := f();; y := y.x;</C>), which previously would have resulted in
an error; see <URL><LinkText>&Hash;457</LinkText><Link>https://github.com/gap-system/gap/issues/457</Link></URL>
and <URL><LinkText>&Hash;462</LinkText><Link>https://github.com/gap-system/gap/pull/462</Link></URL>).
</Item>
<Item>
The libraries of small, primitive and transitive groups which previously
were an integral part of &GAP; were split into three separate packages
<URL Text="PrimgGrp">http://gap-packages.github.io/primgrp/</URL>,
<URL Text="SmallGrp">https://gap-packages.github.io/smallgrp/</URL> and
<URL Text="TransGrp">http://www.math.colostate.edu/~hulpke/transgrp/</URL>.
For backwards compatibility, these are required packages in &GAP; 4.9 (i.e.,
&GAP; will not start without them). We plan to change this for &GAP; 4.10
(see <URL><LinkText>&Hash;2434</LinkText><Link>https://github.com/gap-system/gap/pull/2434</Link></URL>),
once all packages which currently implicitly rely on these
new packages had time to add explicit dependencies on them
(<URL><LinkText>&Hash;1650</LinkText><Link>https://github.com/gap-system/gap/pull/1650</Link></URL>,
<URL><LinkText>&Hash;1714</LinkText><Link>https://github.com/gap-system/gap/pull/1714</Link></URL>).
</Item>
<Item>
The performance of &GAP;'s sorting functions (such as
<Ref BookName="ref" Oper="Sort"/>, <Ref BookName="ref" Oper="SortParallel"/>,
etc.) has been substantially improved, in some examples by more than
a factor of four: as a trivial example, compare the timing for
<C>Sort([1..100000000] * 0)</C>. As a side effect, the result
of sorting lists with equal entries may produce
different answers compared to previous &GAP; versions.
If you would like to make your code independant of the exact
employed sorting algorithm, you can use the newly added
<Ref BookName="ref" Oper="StableSort"/>, <Ref BookName="ref" Oper="StableSortBy"/>
and <Ref BookName="ref" Oper="StableSortParallel"/>. (For some technical details,
see <URL><LinkText>&Hash;609</LinkText><Link>https://github.com/gap-system/gap/pull/609</Link></URL>).
</Item>
<Item>
We removed our old home-grown big integer code, and instead always use the
GMP based big integer code. This means that the GMP library now is a
required dependency, not just an optional one. 
Note that GAP has been using GMP big integer arithmetic for a long time
by default, and we also have been bundling GMP with GAP. So this change
mostly removed code that was never in use for most users.
</Item>
<Item>
A number of improvements have been made to <Ref BookName="ref" Oper="Random"/>. 
These may lead to different sequences of numbers being created.
On the up side, many more methods for <Ref BookName="ref" Oper="Random"/>
(and other <C>RandomXYZ</C> operations) now optionally take an explicit
<Ref BookName="ref" Oper="RandomSource"/> as first argument
(but not yet all: help with issue
<URL><LinkText>&Hash;1098</LinkText><Link>https://github.com/gap-system/gap/pull/1098</Link></URL>
is welcome). Some relevant pull requests:
<List>
<Item>
    Allow creating random permutations using a random source
   (<URL><LinkText>&Hash;1165</LinkText><Link>https://github.com/gap-system/gap/pull/1165</Link></URL>)
</Item>
<Item>
    Let more <Ref BookName="ref" Oper="Random"/> methods use an alternative source
    (<URL><LinkText>&Hash;1168</LinkText><Link>https://github.com/gap-system/gap/pull/1168</Link></URL>)
</Item>
<Item>
    Help <Ref BookName="ref" Oper="Random"/> methods to
    use <Ref BookName="ref" Oper="RandomSource"/>
    (<URL><LinkText>&Hash;810</LinkText><Link>https://github.com/gap-system/gap/pull/810</Link></URL>)
</Item>
<Item>
    Remove uses of old random generator
    (<URL><LinkText>&Hash;808</LinkText><Link>https://github.com/gap-system/gap/pull/808</Link></URL>)
</Item>
<Item>
    Fix <Ref BookName="ref" Oper="Random"/> on long (>2^28) lists
    (<URL><LinkText>&Hash;781</LinkText><Link>https://github.com/gap-system/gap/pull/781</Link></URL>)
</Item>
<Item>
    Fix <Ref BookName="ref" Func="RandomUnimodularMat"/>
    (<URL><LinkText>&Hash;1511</LinkText><Link>https://github.com/gap-system/gap/pull/1511</Link></URL>)
</Item>
<Item>
    Use <Ref BookName="ref" Oper="RandomSource"/> in a few more places
    (<URL><LinkText>&Hash;1599</LinkText><Link>https://github.com/gap-system/gap/pull/1599</Link></URL>)
</Item>
</List>
</Item>
<Item>
The output and behaviour of the profiling system has been substantially improved:
<List>
<Item>
    Make profiling correctly handle the same file being opened multiple times
    (<URL><LinkText>&Hash;1069</LinkText><Link>https://github.com/gap-system/gap/pull/1069</Link></URL>)
</Item>
<Item>
    Do not profile the <C>return</C> statements
    (<Ref BookName="ref" Label="return"/>) inserted into the end of functions
    (<URL><LinkText>&Hash;1073</LinkText><Link>https://github.com/gap-system/gap/pull/1073</Link></URL>)
</Item>
<Item>
    Ensure we reset <C>OutputtedFilenameList</C>
    in profiling when a workspace is restored
    (<URL><LinkText>&Hash;1164</LinkText><Link>https://github.com/gap-system/gap/pull/1164</Link></URL>)
</Item>
<Item>
    Better tracking of amounts of memory allocated and time spent
    in the garbage collector
    (<URL><LinkText>&Hash;1806</LinkText><Link>https://github.com/gap-system/gap/pull/1806</Link></URL>)
</Item>
<Item>
    Allow profiling of memory usage
    (<URL><LinkText>&Hash;1808</LinkText><Link>https://github.com/gap-system/gap/pull/1808</Link></URL>)
</Item>
<Item>
    Remove profiling limit on files with &lt;= 2^16 lines
    (<URL><LinkText>&Hash;1913</LinkText><Link>https://github.com/gap-system/gap/pull/1913</Link></URL>)
</Item>
</List>
</Item>
<Item>
In many cases &GAP; now outputs the filename and location of functions in
helpful places, e.g. in error messages or when displaying compiled functions.
We also try to always use the format <C>FILENAME:LINE</C>, which various
utilities already know how to parse (e.g. in <Package>iTerm2</Package>,
cmd-clicking on such a string can be configured to open an editor
for the file at the indicated line). For some technical details,
see <URL><LinkText>&Hash;469</LinkText><Link>https://github.com/gap-system/gap/pull/469</Link></URL>,
<URL><LinkText>&Hash;755</LinkText><Link>https://github.com/gap-system/gap/pull/755)</Link></URL>,
<URL><LinkText>&Hash;1058</LinkText><Link>https://github.com/gap-system/gap/pull/1058</Link></URL>.
</Item>
<Item>
&GAP; now supports constant variables, whose value cannot
change anymore during runtime; code using such constants can
then be slightly optimized by &GAP;. E.g. if <C>foo</C> is turned
into a constant variable bound to the value <K>false</K>, then &GAP;
can optimize <C>if foo then ... fi;</C> blocks completely away.
For details, see <Ref BookName="ref" Func="MakeConstantGlobal"/> in
<Ref BookName="ref" Sect="More About Global Variables"/>.
(<URL><LinkText>&Hash;1682</LinkText><Link>https://github.com/gap-system/gap/pull/1682</Link></URL>,
<URL><LinkText>&Hash;1770</LinkText><Link>https://github.com/gap-system/gap/pull/1770</Link></URL>)
</Item>
</List>

Other changes:
<List>
<Item>
Enhance <Ref BookName="ref" Attr="StructureDescription"/> with a major rewrite, 
enhancing <C>DirectFactorsOfGroup"</C> and adding 
<C>SemidirectDecompositions</C>;
the core algorithm now also works for infinite abelian groups. Further,
it became faster by quickly finding abelian direct factors and recognizing
several cases where the group is direct indecomposable.
(<URL><LinkText>&Hash;379</LinkText><Link>https://github.com/gap-system/gap/pull/379</Link></URL>, 
<URL><LinkText>&Hash;763</LinkText><Link>https://github.com/gap-system/gap/pull/763</Link></URL>, 
<URL><LinkText>&Hash;985</LinkText><Link>https://github.com/gap-system/gap/pull/985</Link></URL>)
</Item>
<Item>
Mark <Ref BookName="ref" Attr="FittingSubgroup"/> and
<Ref BookName="ref" Attr="FrattiniSubgroup"/> as nilpotent
(<URL><LinkText>&Hash;400</LinkText><Link>https://github.com/gap-system/gap/pull/400</Link></URL>)
</Item>
<Item>
Add method for <Ref BookName="ref" Attr="Socle"/> for finite nilpotent groups
(<URL><LinkText>&Hash;402</LinkText><Link>https://github.com/gap-system/gap/pull/402</Link></URL>)
</Item>
<Item>
Change <Ref BookName="ref" Oper="ViewString"/> and
<Ref BookName="ref" Attr="String"/> methods for various
inverse semigroups and monoids
(<URL><LinkText>&Hash;438</LinkText><Link>https://github.com/gap-system/gap/pull/438</Link></URL>, 
<URL><LinkText>&Hash;880</LinkText><Link>https://github.com/gap-system/gap/pull/880</Link></URL>,
<URL><LinkText>&Hash;882</LinkText><Link>https://github.com/gap-system/gap/pull/882</Link></URL>)
</Item>
<Item>
Enhance some nilpotent and <M>p</M>-group attributes
(<URL><LinkText>&Hash;442</LinkText><Link>https://github.com/gap-system/gap/pull/442</Link></URL>)
</Item>
<Item>
Improve <Ref BookName="ref" Func="Union"/> for a list with many ranges
(<URL><LinkText>&Hash;444</LinkText><Link>https://github.com/gap-system/gap/pull/444</Link></URL>)
</Item>
<Item>
Add <Ref BookName="ref" Func="UserHomeExpand"/>, a function
to expand <C>~</C> in filenames.
(<URL><LinkText>&Hash;447</LinkText><Link>https://github.com/gap-system/gap/pull/447</Link></URL>)
</Item>
<Item>
Extra hint in <Q>No Method Found</Q> error message 
if one of the arguments is <K>fail</K>
(<URL><LinkText>&Hash;460</LinkText><Link>https://github.com/gap-system/gap/pull/460</Link></URL>)
</Item>
<Item>
Tell Sylow subgroups of natural <M>A_n</M> or <M>S_n</M>
their size when we make them
(<URL><LinkText>&Hash;529</LinkText><Link>https://github.com/gap-system/gap/pull/529</Link></URL>)
</Item>
<Item>
Some small enhancements on Sylow and Hall subgroup computations,
mostly for nilpotent groups.
(<URL><LinkText>&Hash;535</LinkText><Link>https://github.com/gap-system/gap/pull/535</Link></URL>)
</Item>
<Item>
Remove <File>.zoo</File> archive related tools
(<URL><LinkText>&Hash;540</LinkText><Link>https://github.com/gap-system/gap/pull/540</Link></URL>)
</Item>
<Item>
Add new <Ref BookName="ref" Attr="FrattiniSubgroup"/>,
<Ref BookName="ref" Attr="MaximalNormalSubgroups"/>, 
<Ref BookName="ref" Attr="MinimalNormalSubgroups"/> and
<Ref BookName="ref" Attr="Socle"/> methods for abelian and/or
solvable groups, even infinite ones. The new methods are only
triggered if the group already knows that it is abelian and/or solvable.
(<URL><LinkText>&Hash;552</LinkText><Link>https://github.com/gap-system/gap/pull/552</Link></URL>,
<URL><LinkText>&Hash;583</LinkText><Link>https://github.com/gap-system/gap/pull/583</Link></URL>,
<URL><LinkText>&Hash;606</LinkText><Link>https://github.com/gap-system/gap/pull/606</Link></URL>)
</Item>
<Item>
New attribute <C>NormalHallSubgroups</C>,
returning a list of all normal Hall subgroups of a group.
(<URL><LinkText>&Hash;561</LinkText><Link>https://github.com/gap-system/gap/pull/561</Link></URL>)
</Item>
<Item>
Add <Ref BookName="ref" Oper="ComplementClassesRepresentatives"/>
fallback method for arbitrary groups
(<URL><LinkText>&Hash;563</LinkText><Link>https://github.com/gap-system/gap/pull/563</Link></URL>)
</Item>
<Item>
(<URL><LinkText>&Hash;612</LinkText><Link>https://github.com/gap-system/gap/pull/612</Link></URL>)
Add parsing of hex literals in strings, e.g. <C>"\0x61"</C> is 
turned into <C>"a"</C>
(<URL><LinkText>&Hash;612</LinkText><Link>https://github.com/gap-system/gap/pull/612</Link></URL>)
</Item>
<Item>
Collection of enhancements
(<URL><LinkText>&Hash;683</LinkText><Link>https://github.com/gap-system/gap/pull/683</Link></URL>)
</Item>
<Item>
Various speed improvements to polynomial factorisation and the &GAP; MeatAxe
(<URL><LinkText>&Hash;720</LinkText><Link>https://github.com/gap-system/gap/pull/720</Link></URL>,
<URL><LinkText>&Hash;1027</LinkText><Link>https://github.com/gap-system/gap/pull/1027</Link></URL>)
</Item>
<Item>
The code and documentation for transformations is improved and
corrected in many instances
(<URL><LinkText>&Hash;727</LinkText><Link>https://github.com/gap-system/gap/pull/727</Link></URL>,
<URL><LinkText>&Hash;732</LinkText><Link>https://github.com/gap-system/gap/pull/732</Link></URL>)
</Item>
<Item>
Change <C>RootFFE</C> to optionally takes a field or
field size as first argument, from which the roots will be taken
(<URL><LinkText>&Hash;761</LinkText><Link>https://github.com/gap-system/gap/pull/761</Link></URL>)
</Item>
<Item>
Change <Ref BookName="ref" Attr="Permanent"/> from a global
function to an attribute
(<URL><LinkText>&Hash;777</LinkText><Link>https://github.com/gap-system/gap/pull/777</Link></URL>)
</Item>
<Item>
Add <Ref BookName="ref" Oper="CallFuncListWrap"/> to wrap return value to
allow distinguishing between functions which return and functions which don't
(<URL><LinkText>&Hash;824</LinkText><Link>https://github.com/gap-system/gap/pull/824</Link></URL>)
</Item>
<Item>
Allow repeated use of same <Ref BookName="ref" Func="DeclareSynonym"/> call
(<URL><LinkText>&Hash;835</LinkText><Link>https://github.com/gap-system/gap/pull/835</Link></URL>)
</Item>
<Item>
New implementation of modified Todd-Coxeter (the old one had bugs,
see <URL><LinkText>&Hash;302</LinkText><Link>https://github.com/gap-system/gap/issues/302</Link></URL>),
<URL><LinkText>&Hash;843</LinkText><Link>https://github.com/gap-system/gap/pull/843</Link></URL>)
</Item>
<Item>
New functionality: Cannon/Holt automorphisms and others
(<URL><LinkText>&Hash;878</LinkText><Link>https://github.com/gap-system/gap/pull/878</Link></URL>)
</Item>
<Item>
Add <Ref BookName="ref" Prop="IsPowerfulPGroup"/> property,
and a <Ref BookName="ref" Attr="FrattiniSubgroup"/> method for
powerful <M>p</M>-groups
(<URL><LinkText>&Hash;894</LinkText><Link>https://github.com/gap-system/gap/pull/894</Link></URL>)
</Item>
<Item>
Improve performance for group isomorphism/automorphisms
(<URL><LinkText>&Hash;896</LinkText><Link>https://github.com/gap-system/gap/pull/896</Link></URL>,
<URL><LinkText>&Hash;968</LinkText><Link>https://github.com/gap-system/gap/pull/968</Link></URL>)
</Item>
<Item>
Make <Ref BookName="ref" Func="ListX"/>,
<Ref BookName="ref" Func="SetX"/>,
<Ref BookName="ref" Func="SumX"/> and 
<Ref BookName="ref" Func="ProductX"/>
support lists which are not collections
(<URL><LinkText>&Hash;903</LinkText><Link>https://github.com/gap-system/gap/pull/903</Link></URL>)
</Item>
<Item>
Some improvements for <Ref BookName="ref" Func="LatticeByCyclicExtension"/>
(<URL><LinkText>&Hash;905</LinkText><Link>https://github.com/gap-system/gap/pull/905</Link></URL>)
</Item>
<Item>
Add helpers to retrieve information about operations and filters:
<Ref BookName="ref" Func="CategoryByName"/>,
<Ref BookName="ref" Func="TypeOfOperation"/>, 
<Ref BookName="ref" Func="FilterByName"/>,
<Ref BookName="ref" Oper="FiltersObj"/>,
<Ref BookName="ref" Oper="FiltersType"/>,
<C>IdOfFilter</C>,
<C>IdOfFilterByName</C>,
<Ref BookName="ref" Func="IsAttribute"/>,
<Ref BookName="ref" Func="IsCategory"/>,
<Ref BookName="ref" Func="IsProperty"/>,
<Ref BookName="ref" Func="IsRepresentation"/>
(<URL><LinkText>&Hash;925</LinkText><Link>https://github.com/gap-system/gap/pull/925</Link></URL>,
<URL><LinkText>&Hash;1593</LinkText><Link>https://github.com/gap-system/gap/pull/1593</Link></URL>)
</Item>
<Item>
Add case-insensitive autocomplete
(<URL><LinkText>&Hash;928</LinkText><Link>https://github.com/gap-system/gap/pull/928</Link></URL>)
</Item>
<Item>
Give better error message if a help file is missing
(<URL><LinkText>&Hash;939</LinkText><Link>https://github.com/gap-system/gap/pull/939</Link></URL>)
</Item>
<Item>
Add <Ref BookName="ref" Func="LowercaseChar"/> and
<Ref BookName="ref" Func="UppercaseChar"/>
(<URL><LinkText>&Hash;952</LinkText><Link>https://github.com/gap-system/gap/pull/952</Link></URL>)
</Item>
<Item>
Add <Ref BookName="ref" Func="PositionMaximum"/> and
<Ref BookName="ref" Func="PositionMinimum"/>
(<URL><LinkText>&Hash;956</LinkText><Link>https://github.com/gap-system/gap/pull/956</Link></URL>)
</Item>
<Item>
Switching default command history length from infinity to 1000
(<URL><LinkText>&Hash;960</LinkText><Link>https://github.com/gap-system/gap/pull/960</Link></URL>)
</Item>
<Item>
Allow conversion of <C>-infinity</C> to float via
<Ref BookName="ref" Constr="NewFloat"/> and 
<Ref BookName="ref" Oper="MakeFloat"/>
(<URL><LinkText>&Hash;961</LinkText><Link>https://github.com/gap-system/gap/pull/961</Link></URL>)
</Item>
<Item>
Add option <C>NoPrecomputedData</C> to avoid use of data libraries
in certain computations (useful if one wants to verify the
content of these data libraries)
(<URL><LinkText>&Hash;986</LinkText><Link>https://github.com/gap-system/gap/pull/986</Link></URL>)
</Item>
<Item>
Remove one-argument version of <Ref BookName="ref" Oper="AsPartialPerm"/>
for a transformation
(<URL><LinkText>&Hash;1036</LinkText><Link>https://github.com/gap-system/gap/pull/1036</Link></URL>)
</Item>
<Item>
Partial perms now have a <Ref BookName="ref" Attr="MultiplicativeZero"/>
rather than a <Ref BookName="ref" Attr="Zero"/>, since they are
multiplicative rather than additive elements
(<URL><LinkText>&Hash;1040</LinkText><Link>https://github.com/gap-system/gap/pull/1040</Link></URL>)
</Item>
<Item>
Various enhancements:
(<URL><LinkText>&Hash;1046</LinkText><Link>https://github.com/gap-system/gap/pull/1046</Link></URL>)
<List>
<Item>
A bugfix in <Ref BookName="ref" Oper="NaturalHomomorphismByIdeal"/>
for polynomial rings
</Item>
<Item>
Improvements in handling solvable permutation groups
</Item>
<Item>
The trivial group now is a member of the perfect groups library
</Item>
<Item>
Improvements in using tabulated data for maximal subgroups
</Item>
</List>    
</Item>
<Item>
New tests for group constructors and some fixes
(e.g. <C>GO(1,4,5)</C> used to trigger an error)
(<URL><LinkText>&Hash;1053</LinkText><Link>https://github.com/gap-system/gap/pull/1053</Link></URL>)
</Item>
<Item>
Make <C>HasSolvableFactorGroup</C> slightly more efficient
(<URL><LinkText>&Hash;1062</LinkText><Link>https://github.com/gap-system/gap/pull/1062</Link></URL>)
</Item>
<Item>
Enhance <C>HasXXFactorGroup</C>
(<URL><LinkText>&Hash;1066</LinkText><Link>https://github.com/gap-system/gap/pull/1066</Link></URL>)
</Item>
<Item>
Remove GAP4stones from tests
(<URL><LinkText>&Hash;1072</LinkText><Link>https://github.com/gap-system/gap/pull/1072</Link></URL>)
</Item>
<Item>
<Ref BookName="ref" Oper="AsMonoid"/> and
<Ref BookName="ref" Oper="AsSemigroup"/> are now operations, and various bugs
were resolved related to isomorphisms of semigroups and monoids
(<URL><LinkText>&Hash;1112</LinkText><Link>https://github.com/gap-system/gap/pull/1112</Link></URL>)
</Item>
<Item>
Mark isomorphisms between trivial groups as bijective
(<URL><LinkText>&Hash;1116</LinkText><Link>https://github.com/gap-system/gap/pull/1116</Link></URL>)
</Item>
<Item>
Speed up <Ref BookName="ref" Func="RootMod"/> and
<Ref BookName="ref" Oper="RootsMod"/> for moduli with large
prime factors; also add <C>IS_PROBAB_PRIME_INT</C> kernel function
(<URL><LinkText>&Hash;1141</LinkText><Link>https://github.com/gap-system/gap/pull/1141</Link></URL>)
</Item>
<Item>
The search for the documentation of system setters and testers
now returns corresponding attributes and properties
(<URL><LinkText>&Hash;1144</LinkText><Link>https://github.com/gap-system/gap/pull/1144</Link></URL>)
</Item>
<Item>
Remove command line options <C>-c</C>, <C>-U</C>, <C>-i</C>
and <C>-X</C>, add <C>--quitonbreak</C>
(<URL><LinkText>&Hash;1192</LinkText><Link>https://github.com/gap-system/gap/pull/1192</Link></URL>,
<URL><LinkText>&Hash;1265</LinkText><Link>https://github.com/gap-system/gap/pull/1265</Link></URL>,
<URL><LinkText>&Hash;1421</LinkText><Link>https://github.com/gap-system/gap/pull/1421</Link></URL>,
<URL><LinkText>&Hash;1448</LinkText><Link>https://github.com/gap-system/gap/pull/1448</Link></URL>)
</Item>
<Item>
Remove Itanium support
(<URL><LinkText>&Hash;1163</LinkText><Link>https://github.com/gap-system/gap/pull/1163</Link></URL>)
</Item>
<Item>
Adding two strings now shows a more helpful error message
(<URL><LinkText>&Hash;1314</LinkText><Link>https://github.com/gap-system/gap/pull/1314</Link></URL>)
</Item>
<Item>
Suppress <C>Unbound global variable</C> warning in
<Ref BookName="ref" Func="IsBound" Label="for a global variable"/>
(<URL><LinkText>&Hash;1334</LinkText><Link>https://github.com/gap-system/gap/pull/1334</Link></URL>)
</Item>
<Item>
Increase warning level for Conway polynomial
(<URL><LinkText>&Hash;1363</LinkText><Link>https://github.com/gap-system/gap/pull/1363</Link></URL>)
</Item>
<Item>
Performance improvements to maximal and intermediate subgroups,
fix of <Ref BookName="ref" Func="RepresentativeAction"/>
(<URL><LinkText>&Hash;1390</LinkText><Link>https://github.com/gap-system/gap/pull/1390</Link></URL>)
</Item>
<Item>
Revise Chapter 52 of the reference manual (fp semigroups and monoids)
(<URL><LinkText>&Hash;1441</LinkText><Link>https://github.com/gap-system/gap/pull/1441</Link></URL>)
</Item>
<Item>
Improve the performance of the <C>Info</C>
(<Ref BookName="ref" Label="Info"/>) statement
(<URL><LinkText>&Hash;1464</LinkText><Link>https://github.com/gap-system/gap/pull/1464</Link></URL>,
<URL><LinkText>&Hash;1770</LinkText><Link>https://github.com/gap-system/gap/pull/1770</Link></URL>)
</Item>
<Item>
When printing function bodies, avoid some redundant spaces
(<URL><LinkText>&Hash;1498</LinkText><Link>https://github.com/gap-system/gap/pull/1498</Link></URL>)
</Item>
<Item>
Add kernel functions for directly accessing entries of GF2/8bit compressed matrices
(<URL><LinkText>&Hash;1585</LinkText><Link>https://github.com/gap-system/gap/pull/1585</Link></URL>)
</Item>
<Item>
Add <Ref BookName="ref" Attr="String"/> method for functions
(<URL><LinkText>&Hash;1591</LinkText><Link>https://github.com/gap-system/gap/pull/1591</Link></URL>)
</Item>
<Item>
Check modules were compiled with the same version of &GAP; when loading them
(<URL><LinkText>&Hash;1600</LinkText><Link>https://github.com/gap-system/gap/pull/1600</Link></URL>)
</Item>
<Item>
When printing function, reproduce <C>TryNextMethod()</C> correctly
(<URL><LinkText>&Hash;1613</LinkText><Link>https://github.com/gap-system/gap/pull/1613</Link></URL>)
</Item>
<Item>
New <Q>Bitfields</Q> feature (<Ref BookName="ref" Label="Bitfields"/>)
providing efficient support for packing multiple data items into a single
word for cache and memory efficiency
(<URL><LinkText>&Hash;1616</LinkText><Link>https://github.com/gap-system/gap/pull/1616</Link></URL>)
</Item>
<Item>
Improved <File>bin/BuildPackages.sh</File>, in particular
    added option to abort upon failure
    (<URL><LinkText>&Hash;2022</LinkText><Link>https://github.com/gap-system/gap/pull/2022</Link></URL>) 
</Item>
<Item>
Rewrote integer code (GMP) for better performance of certain
large integer operations, and added kernel implementations of
various functions, including these:
<List>
<Item>
    Add kernel implementations of <Ref BookName="ref" Func="AbsInt"/>,
    <Ref BookName="ref" Func="SignInt"/>; 
    add new kernel functions <C>ABS_RAT</C>, <C>SIGN_RAT</C>; 
    and speed up <Ref BookName="ref" Label="mod"/>,
    <Ref BookName="ref" Func="RemInt"/>,
    <Ref BookName="ref" Func="QuoInt"/>
    for divisors which are small powers of 2
    (<URL><LinkText>&Hash;1045</LinkText><Link>https://github.com/gap-system/gap/pull/1045</Link></URL>)
</Item>
<Item>
    Add kernel implementations of <Ref BookName="ref" Func="Jacobi"/>,
    <Ref BookName="ref" Func="PowerModInt"/>,
    <Ref BookName="ref" Oper="Valuation"/> (for integers),
    <Ref BookName="ref" Func="PValuation"/> (for integers)
    (<URL><LinkText>&Hash;1075</LinkText><Link>https://github.com/gap-system/gap/pull/1045</Link></URL>)
</Item>
<Item>
    Add kernel implementation of <Ref BookName="ref" Func="Factorial"/>
    (<URL><LinkText>&Hash;1969</LinkText><Link>https://github.com/gap-system/gap/pull/1969</Link></URL>)
</Item>
<Item>
    Add kernel implementation of <Ref BookName="ref" Func="Binomial"/>
    (<URL><LinkText>&Hash;1921</LinkText><Link>https://github.com/gap-system/gap/pull/1921</Link></URL>)
</Item>
<Item>
    Add kernel implementation of <Ref BookName="ref" Func="LcmInt"/>
    (<URL><LinkText>&Hash;2019</LinkText><Link>https://github.com/gap-system/gap/pull/2019</Link></URL>)
</Item>
</List>    
</Item>
<Item>
Check version of kernel for package versions
(<URL><LinkText>&Hash;1600</LinkText><Link>https://github.com/gap-system/gap/pull/1600</Link></URL>)
</Item>
<Item>
Add new <Ref BookName="ref" Oper="AlgebraicExtensionNC"/> operation
(<URL><LinkText>&Hash;1665</LinkText><Link>https://github.com/gap-system/gap/pull/1665</Link></URL>)
</Item>
<Item>
Add <C>NumberColumns</C> and <C>NumberRows</C> to <C>MatrixObj</C> interface
(<URL><LinkText>&Hash;1657</LinkText><Link>https://github.com/gap-system/gap/pull/1657</Link></URL>)
</Item>
<Item>
<Ref BookName="ref" Attr="MinimalGeneratingSet"/> returns an answer for
non-cyclic groups that already have a generating set of size 2 (which
hence is minimal)
(<URL><LinkText>&Hash;1755</LinkText><Link>https://github.com/gap-system/gap/pull/1755</Link></URL>)
</Item>
<Item>
Add <Ref BookName="ref" Oper="GetWithDefault"/> which returns the <M>n</M>-th
element of the list if it is bound, and the default value otherwise
(<URL><LinkText>&Hash;1762</LinkText><Link>https://github.com/gap-system/gap/pull/1762</Link></URL>)
</Item>
<Item>
Fast method for <C>ElmsBlist</C> when positions are a range with increment 1
(<URL><LinkText>&Hash;1773</LinkText><Link>https://github.com/gap-system/gap/pull/1773</Link></URL>)
</Item>
<Item>
Make permutations remember their inverses
(<URL><LinkText>&Hash;1831</LinkText><Link>https://github.com/gap-system/gap/pull/1831</Link></URL>)
</Item>
<Item>
Add invariant forms for <C>GU(1,q)</C> and <C>SU(1,q)</C>
(<URL><LinkText>&Hash;1874</LinkText><Link>https://github.com/gap-system/gap/pull/1874</Link></URL>)
</Item>
<Item>
Implement <Ref BookName="ref" Oper="StandardAssociate"/> and
<Ref BookName="ref" Oper="StandardAssociateUnit"/>
for <Ref BookName="ref" Func="ZmodnZ"/>, clarify documentation
for <Ref BookName="ref" Filt="IsEuclideanRing"/>
(<URL><LinkText>&Hash;1990</LinkText><Link>https://github.com/gap-system/gap/pull/1990</Link></URL>)
</Item>
<Item>
Improve documentation and interface for floats
(<URL><LinkText>&Hash;2016</LinkText><Link>https://github.com/gap-system/gap/pull/2016</Link></URL>)
</Item>
<Item>
Add <Ref BookName="ref" Oper="PositionsProperty"/> method for non-dense lists
(<URL><LinkText>&Hash;2021</LinkText><Link>https://github.com/gap-system/gap/pull/2021</Link></URL>)
</Item>
<Item>
Add <C>TrivialGroup(IsFpGroup)</C>
(<URL><LinkText>&Hash;2037</LinkText><Link>https://github.com/gap-system/gap/pull/2037</Link></URL>)
</Item>
<Item>
Change <Ref BookName="ref" Func="ObjectifyWithAttributes"/> to
return the new objects
(<URL><LinkText>&Hash;2098</LinkText><Link>https://github.com/gap-system/gap/pull/2098</Link></URL>)
</Item>
<Item>
Removed a never released undocumented &HPCGAP; syntax extension which allowed to
use a backtick/backquote as alias for <Ref BookName="ref" Func="MakeImmutable"/>.
(<URL><LinkText>&Hash;2202</LinkText><Link>https://github.com/gap-system/gap/pull/2202</Link></URL>).
</Item>
<Item>
Various changes (<URL><LinkText>&Hash;2253</LinkText><Link>https://github.com/gap-system/gap/pull/2253</Link></URL>):
<List>
<Item>
    Improve performance and memory usage of <C>ImageKernelBlocksHomomorphism"</C>
</Item>
<Item>
    Document <Ref BookName="ref" Oper="LowIndexSubgroups"/>
</Item>
<Item>
    Correct <Ref BookName="ref" Func="ClassesSolvableGroup"/> documentation to clarify that it requires, but does not test membership
</Item>
<Item>
    fix <Ref BookName="ref" Filt="IsNaturalGL"/> for trivial matrix groups with empty generating set
</Item>
</List>  
</Item>
<Item>
Make it possible to interrupt <C>repeat continue; until false;</C> and
similar tight loops with <Q>Ctrl-C</Q>
(<URL><LinkText>&Hash;2259</LinkText><Link>https://github.com/gap-system/gap/pull/2259</Link></URL>).
</Item>
<Item>
Improved &GAP; testing infrastructure, extended &GAP; test suite,
and increased code coverage
</Item>
<Item>
Countless other tweaks, improvements, fixes were applied
to the &GAP; library, kernel and manual
</Item>
</List>

Fixed bugs:
<List>
<Item>
Fix bugs in <Ref BookName="ref" Attr="NormalSubgroups"/> and
<Ref BookName="ref" Func="PrintCSV"/>
(<URL><LinkText>&Hash;433</LinkText><Link>https://github.com/gap-system/gap/pull/433</Link></URL>)
</Item>
<Item>
Fix nice monomorphism dispatch for <Ref BookName="ref" Attr="HallSubgroup"/>
(e.g. fixes <C>HallSubgroup(GL(3,4), [2,3])</C>)
(<URL><LinkText>&Hash;559</LinkText><Link>https://github.com/gap-system/gap/pull/559</Link></URL>)
</Item>
<Item>
Check for permutations whose degree would exceed the internal limit,
and document that limit
(<URL><LinkText>&Hash;581</LinkText><Link>https://github.com/gap-system/gap/pull/581</Link></URL>)
</Item>
<Item>
Fix segfault after quitting from the break loop in certain cases
(<URL><LinkText>&Hash;709</LinkText><Link>https://github.com/gap-system/gap/pull/709</Link></URL> which
fixes <URL><LinkText>&Hash;397</LinkText><Link>https://github.com/gap-system/gap/issues/397</Link></URL>)
</Item>
<Item>
Fix rankings for <Ref BookName="ref" Attr="Socle"/> and
<Ref BookName="ref" Attr="MinimalNormalSubgroups"/>
(<URL><LinkText>&Hash;711</LinkText><Link>https://github.com/gap-system/gap/pull/711</Link></URL>)
</Item>
<Item>
Make key and attribute values immutable
(<URL><LinkText>&Hash;714</LinkText><Link>https://github.com/gap-system/gap/pull/714</Link></URL>)
</Item>
<Item>
Make <C>OnTuples([-1], (1,2))</C> return an error
(<URL><LinkText>&Hash;718</LinkText><Link>https://github.com/gap-system/gap/pull/718</Link></URL>)
</Item>
<Item>
Fix bug in <Ref BookName="ref" Attr="NewmanInfinityCriterion"/>
which could corrupt the <Ref BookName="ref" Attr="PCentralSeries"/> attribute
(<URL><LinkText>&Hash;719</LinkText><Link>https://github.com/gap-system/gap/pull/719</Link></URL>)
</Item>
<Item>
The length of the list returned by <C>OnSetsPerm</C> is now properly set
(<URL><LinkText>&Hash;731</LinkText><Link>https://github.com/gap-system/gap/pull/731</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Oper="Remove"/> misbehaving when
last member of list with gaps in it is removed
(<URL><LinkText>&Hash;766</LinkText><Link>https://github.com/gap-system/gap/pull/766</Link></URL>)
</Item>
<Item>
Fix bugs in various methods for Rees (0-)matrix semigroups:
<Ref BookName="ref" Prop="IsFinite"/>,
<Ref BookName="ref" Prop="IsOne"/>,
<Ref BookName="ref" Attr="Enumerator"/>,
<Ref BookName="ref" Prop="IsReesMatrixSemigroup"/> and
<Ref BookName="ref" Prop="IsReesZeroMatrixSemigroup"/>
(<URL><LinkText>&Hash;768</LinkText><Link>https://github.com/gap-system/gap/pull/768</Link></URL>,
<URL><LinkText>&Hash;1676</LinkText><Link>https://github.com/gap-system/gap/pull/1676</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Prop="IsFullTransformationSemigroup"/>
to work correctly for the full transformation semigroup of degree 0
(<URL><LinkText>&Hash;769</LinkText><Link>https://github.com/gap-system/gap/pull/769</Link></URL>)
</Item>
<Item>
Fix printing very large (> 2^28 points) permutations
(<URL><LinkText>&Hash;782</LinkText><Link>https://github.com/gap-system/gap/pull/782</Link></URL>)
</Item>
<Item>
Fix <C>Intersection([])</C>
(<URL><LinkText>&Hash;854</LinkText><Link>https://github.com/gap-system/gap/pull/854</Link></URL>)
</Item>
<Item>
Fix crash in <C>IsKernelFunction</C> for some inputs
(<URL><LinkText>&Hash;876</LinkText><Link>https://github.com/gap-system/gap/pull/876</Link></URL>)
</Item>
<Item>
Fix bug in <Ref BookName="ref" Func="ShortestVectors"/> which could cause
<Ref BookName="ref" Func="OrthogonalEmbeddings"/> to enter a break loop
(<URL><LinkText>&Hash;941</LinkText><Link>https://github.com/gap-system/gap/pull/941</Link></URL>)
</Item>
<Item>
Fix crash in some methods involving partial perms
(<URL><LinkText>&Hash;948</LinkText><Link>https://github.com/gap-system/gap/pull/948</Link></URL>)
</Item>
<Item>
<C>FreeMonoid(0)</C> no longer satisfies <Ref BookName="ref" Filt="IsGroup"/>
(<URL><LinkText>&Hash;950</LinkText><Link>https://github.com/gap-system/gap/pull/950</Link></URL>)
</Item>
<Item>
Fix crash when invoking weak pointer functions on invalid arguments
(<URL><LinkText>&Hash;1009</LinkText><Link>https://github.com/gap-system/gap/pull/1009</Link></URL>)
</Item>
<Item>
Fix a bug parsing character constants
(<URL><LinkText>&Hash;1015</LinkText><Link>https://github.com/gap-system/gap/pull/1015</Link></URL>)
</Item>
<Item>
Fix several bugs and crashes in <C>Z(p,d)</C> for invalid arguments,
e.g. <C>Z(4,5)</C>, <C>Z(6,3)</C>
(<URL><LinkText>&Hash;1029</LinkText><Link>https://github.com/gap-system/gap/pull/1029</Link></URL>,
<URL><LinkText>&Hash;1059</LinkText><Link>https://github.com/gap-system/gap/pull/1059</Link></URL>,
<URL><LinkText>&Hash;1383</LinkText><Link>https://github.com/gap-system/gap/pull/1383</Link></URL>,
<URL><LinkText>&Hash;1573</LinkText><Link>https://github.com/gap-system/gap/pull/1573</Link></URL>)
</Item>
<Item>
Fix starting &GAP; on systems with large inodes
(<URL><LinkText>&Hash;1033</LinkText><Link>https://github.com/gap-system/gap/pull/1033</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Attr="NrFixedPoints"/> and
<Ref BookName="ref" Attr="FixedPointsOfPartialPerm"/> for a partial
perm and a partial perm semigroup (they used to return the moved
points rather than the fixed points)
(<URL><LinkText>&Hash;1034</LinkText><Link>https://github.com/gap-system/gap/pull/1034</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Func="MeetOfPartialPerms"/>
when given a collection of 1 or 0 partial perms
(<URL><LinkText>&Hash;1035</LinkText><Link>https://github.com/gap-system/gap/pull/1035</Link></URL>)
</Item>
<Item>
The behaviour of <Ref BookName="ref" Oper="AsPartialPerm"
Label="for a transformation and a set of positive integer"/>
for a transformation and a list is corrected
(<URL><LinkText>&Hash;1036</LinkText><Link>https://github.com/gap-system/gap/pull/1036</Link></URL>)
</Item>
<Item>
<Ref BookName="ref" Attr="IsomorphismReesZeroMatrixSemigroup"/>
for a 0-simple semigroup is now defined on the zero of the source
and range semigroups
(<URL><LinkText>&Hash;1038</LinkText><Link>https://github.com/gap-system/gap/pull/1038</Link></URL>)
</Item>
<Item>
Fix isomorphisms from finitely-presented monoids to
finitely-presented semigroups, and allow isomorphisms
from semigroups to fp-monoids
(<URL><LinkText>&Hash;1039</LinkText><Link>https://github.com/gap-system/gap/pull/1039</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Attr="One"/> for a partial permutation semigroup
without generators
(<URL><LinkText>&Hash;1040</LinkText><Link>https://github.com/gap-system/gap/pull/1040</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Func="MemoryUsage"/> for positional
and component objects
(<URL><LinkText>&Hash;1044</LinkText><Link>https://github.com/gap-system/gap/pull/1044</Link></URL>)
</Item>
<Item>
Fix <C>PlainString</C> causing immutable strings to become mutable
(<URL><LinkText>&Hash;1096</LinkText><Link>https://github.com/gap-system/gap/pull/1096</Link></URL>)
</Item>
<Item>
Restore support for sparc64
(<URL><LinkText>&Hash;1124</LinkText><Link>https://github.com/gap-system/gap/pull/1124</Link></URL>)
</Item>
<Item>
Fix a problem with `&lt;` for transformations, which could give incorrect results
(<URL><LinkText>&Hash;1130</LinkText><Link>https://github.com/gap-system/gap/pull/1130</Link></URL>)
</Item>
<Item>
Fix crash when comparing recursive data structures such as <C>[~] = [~]</C>
(<URL><LinkText>&Hash;1151</LinkText><Link>https://github.com/gap-system/gap/pull/1151</Link></URL>)
</Item>
<Item>
Ensure output of <C>TrivialGroup(IsPermGroup)</C> has zero generators
(<URL><LinkText>&Hash;1247</LinkText><Link>https://github.com/gap-system/gap/pull/1247</Link></URL>)
</Item>
<Item>
Fix for applying the <Ref BookName="ref" Attr="InverseGeneralMapping"/>
of an <Ref BookName="ref" Attr="IsomorphismFpSemigroup"/>
(<URL><LinkText>&Hash;1259</LinkText><Link>https://github.com/gap-system/gap/pull/1259</Link></URL>)
</Item>
<Item>
Collection of improvements and fixes:
(<URL><LinkText>&Hash;1294</LinkText><Link>https://github.com/gap-system/gap/pull/1294</Link></URL>)
<List>
<Item>
A fix for quotient rings of rings by structure constants
</Item>
<Item>
Generic routine for transformation matrix to rational canonical form
</Item>
<Item>
Speed improvements to block homomorphisms
</Item>
<Item>
New routines for conjugates or subgroups with desired containment
</Item>
<Item>
Performance improvement for conjugacy classes in groups with a huge
number of classes, giving significant improvements to
<Ref BookName="ref" Oper="IntermediateSubgroups"/> (e.g. 7-Sylow subgroup
in <M>PSL(7,2)</M>), ascending chain and thus in turn double coset
calculations and further routines that rely on it
</Item>
</List>          
</Item>
<Item>
Fix <Ref BookName="ref" Oper="EqFloat"/> to return correct results,
instead of always returning <K>false</K>
(<URL><LinkText>&Hash;1370</LinkText><Link>https://github.com/gap-system/gap/pull/1370</Link></URL>)
</Item>
<Item>
Various changes, including fixes for <Ref BookName="ref" Func="CallFuncList"/>
(<URL><LinkText>&Hash;1417</LinkText><Link>https://github.com/gap-system/gap/pull/1417</Link></URL>)
</Item>
<Item>
Better define the result of <Ref BookName="ref" Func="MappingPermListList"/>
(<URL><LinkText>&Hash;1432</LinkText><Link>https://github.com/gap-system/gap/pull/1432</Link></URL>)
</Item>
<Item>
Check the arguments to <Ref BookName="ref" Func="IsInjectiveListTrans"/>
to prevent crashes
(<URL><LinkText>&Hash;1435</LinkText><Link>https://github.com/gap-system/gap/pull/1435</Link></URL>)
</Item>
<Item>
Change <Ref BookName="ref" Func="BlownUpMat"/> to return fail
for certain invalid inputs
(<URL><LinkText>&Hash;1488</LinkText><Link>https://github.com/gap-system/gap/pull/1488</Link></URL>)
</Item>
<Item>
Fixes for creating Green's classes of semigroups
(<URL><LinkText>&Hash;1492</LinkText><Link>https://github.com/gap-system/gap/pull/1492</Link></URL>,
<URL><LinkText>&Hash;1771</LinkText><Link>https://github.com/gap-system/gap/pull/1771</Link></URL>)
</Item>
<Item>
Fix <C>DoImmutableMatrix</C> for finite fields
(<URL><LinkText>&Hash;1504</LinkText><Link>https://github.com/gap-system/gap/pull/1504</Link></URL>)
</Item>
<Item>
Make structural copy handle boolean lists properly
(<URL><LinkText>&Hash;1514</LinkText><Link>https://github.com/gap-system/gap/pull/1514</Link></URL>)
</Item>
<Item>
Minimal fix for algebraic extensions over finite fields of order > 256
(<URL><LinkText>&Hash;1569</LinkText><Link>https://github.com/gap-system/gap/pull/1569</Link></URL>)
</Item>
<Item>
Fix for computing quotients of certain algebra modules
(<URL><LinkText>&Hash;1669</LinkText><Link>https://github.com/gap-system/gap/pull/1669</Link></URL>)
</Item>
<Item>
Fix an error in the default method for <Ref BookName="ref" Oper="PositionNot"/>
(<URL><LinkText>&Hash;1672</LinkText><Link>https://github.com/gap-system/gap/pull/1672</Link></URL>)
</Item>
<Item>
Improvements to Rees matrix semigroups code and new tests
(<URL><LinkText>&Hash;1676</LinkText><Link>https://github.com/gap-system/gap/pull/1676</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Func="CodePcGroup"/>
for the trivial polycyclic group
(<URL><LinkText>&Hash;1679</LinkText><Link>https://github.com/gap-system/gap/pull/1679</Link></URL>)
</Item>
<Item>
Fix <C>FroidurePinExtendedAlg</C> for partial permutation monoids
(<URL><LinkText>&Hash;1697</LinkText><Link>https://github.com/gap-system/gap/pull/1697</Link></URL>)
</Item>
<Item>
Fix computing the radical of a zero dimensional associative algebra
(<URL><LinkText>&Hash;1701</LinkText><Link>https://github.com/gap-system/gap/pull/1701</Link></URL>)
</Item>
<Item>
Fix a bug in <Ref BookName="ref" Attr="RadicalOfAlgebra"/>
which could cause a break loop for some associative algebras
(<URL><LinkText>&Hash;1716</LinkText><Link>https://github.com/gap-system/gap/pull/1716</Link></URL>)
</Item>
<Item>
Fix a recursion depth trap error when repeatedly calling
<Ref BookName="ref" Func="Test"/>
(<URL><LinkText>&Hash;1753</LinkText><Link>https://github.com/gap-system/gap/pull/1753</Link></URL>)
</Item>
<Item>
Fix bugs in <Ref BookName="ref" Attr="PrimePGroup"/> for direct products
of <M>p</M>-groups
(<URL><LinkText>&Hash;1754</LinkText><Link>https://github.com/gap-system/gap/pull/1754</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Func="UpEnv"/> (available in break loops)
when at the bottom of the backtrace
(<URL><LinkText>&Hash;1780</LinkText><Link>https://github.com/gap-system/gap/pull/1780</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Attr="IsomorphismPartialPermSemigroup"/> and
<Ref BookName="ref" Attr="IsomorphismPartialPermMonoid"/> for permutation
groups with 0 generators
(<URL><LinkText>&Hash;1784</LinkText><Link>https://github.com/gap-system/gap/pull/1784</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Oper="DisplaySemigroup"/> for transformation semigroups
(<URL><LinkText>&Hash;1785</LinkText><Link>https://github.com/gap-system/gap/pull/1785</Link></URL>)
</Item>
<Item>
Fix <Q>no method found</Q> errors in <Ref BookName="ref" Func="MagmaWithOne"/>
and <Ref BookName="ref" Func="MagmaWithInverses"/>
(<URL><LinkText>&Hash;1798</LinkText><Link>https://github.com/gap-system/gap/pull/1798</Link></URL>)
</Item>
<Item>
Fix an error computing kernel of group homomorphism from fp group
into permutation group
(<URL><LinkText>&Hash;1809</LinkText><Link>https://github.com/gap-system/gap/pull/1809</Link></URL>)
</Item>
<Item>
Fix an error in MTC losing components when copying a new augmented coset table
(<URL><LinkText>&Hash;1809</LinkText><Link>https://github.com/gap-system/gap/pull/1809</Link></URL>)
</Item>
<Item>
Fix output of <Ref BookName="ref" Func="Where"/> in a break loop,
which pointed at the wrong code line in some cases
(<URL><LinkText>&Hash;1814</LinkText><Link>https://github.com/gap-system/gap/pull/1814</Link></URL>)
</Item>
<Item>
Fix the interaction of signals in &GAP; and the <Package>IO</Package> package
(<URL><LinkText>&Hash;1851</LinkText><Link>https://github.com/gap-system/gap/pull/1851</Link></URL>)
</Item>
<Item>
Make line editing resilient to <C>LineEditKeyHandler</C> failure
(in particular, don't crash)
(<URL><LinkText>&Hash;1856</LinkText><Link>https://github.com/gap-system/gap/pull/1856</Link></URL>)
</Item>
<Item>
Omit non-characters from <Ref BookName="ref" Func="PermChars"/> results
(<URL><LinkText>&Hash;1867</LinkText><Link>https://github.com/gap-system/gap/pull/1867</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Oper="ExteriorPower"/> when exterior power
is 0-dimensional (used to return a 1-dimensional result)
(<URL><LinkText>&Hash;1872</LinkText><Link>https://github.com/gap-system/gap/pull/1872</Link></URL>)
</Item>
<Item>
Fix recursion depth trap and other improvements for quotients of fp groups
(<URL><LinkText>&Hash;1884</LinkText><Link>https://github.com/gap-system/gap/pull/1884</Link></URL>)
</Item>
<Item>
Fix a bug in the computation of a permutation group isomorphic
to a group of automorphisms
(<URL><LinkText>&Hash;1907</LinkText><Link>https://github.com/gap-system/gap/pull/1907</Link></URL>)
</Item>
<Item>
Fix bug in <Ref BookName="ref" Func="InstallFlushableValueFromFunction"/>
(<URL><LinkText>&Hash;1920</LinkText><Link>https://github.com/gap-system/gap/pull/1920</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Attr="ONanScottType"/> and introduce
<Ref BookName="ref" Attr="RestrictedInverseGeneralMapping"/>
(<URL><LinkText>&Hash;1937</LinkText><Link>https://github.com/gap-system/gap/pull/1937</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Oper="QuotientMod"/> documentation, and the integer
implementation. This partially reverts changes made in version 4.7.8 in 2013.
The documentation is now correct (resp. consistent again), and several corner
cases, e.g. <C>QuotientMod(0,0,m)</C> now work correctly
(<URL><LinkText>&Hash;1991</LinkText><Link>https://github.com/gap-system/gap/pull/1991</Link></URL>)
</Item>
<Item>
Fix <Ref BookName="ref" Oper="PositionProperty"/> with <A>from</A> &lt; 1
(<URL><LinkText>&Hash;2056</LinkText><Link>https://github.com/gap-system/gap/pull/2056</Link></URL>)
</Item>
<Item>
Fix inefficiency when dealing with certain algebra modules
(<URL><LinkText>&Hash;2058</LinkText><Link>https://github.com/gap-system/gap/pull/2058</Link></URL>)
</Item>
<Item>
Restrict capacity of plain lists to <M>2^28</M> in 32-bit
and <M>2^60</M> in 64-bit builds
(<URL><LinkText>&Hash;2064</LinkText><Link>https://github.com/gap-system/gap/pull/2064</Link></URL>)
</Item>
<Item>
Fix crashes with very large heaps (> 2 GB) on 32 bit systems, and work around 
a bug in <C>memmove</C> in 32-bit glibc versions which could corrupt memory
(affects most current Linux distributions)
(<URL><LinkText>&Hash;2166</LinkText><Link>https://github.com/gap-system/gap/pull/2166</Link></URL>).
</Item>
<Item>
Fix name of the <C>reversed</C> option in documentation of
<Ref BookName="ref" Func="LoadAllPackages"/>
(<URL><LinkText>&Hash;2167</LinkText><Link>https://github.com/gap-system/gap/pull/2167</Link></URL>).
</Item>
<Item>
Fix <C>TriangulizedMat([])</C> (see <Ref BookName="ref" Oper="TriangulizedMat"/>
to return an empty list instead of producing an error
(<URL><LinkText>&Hash;2260</LinkText><Link>https://github.com/gap-system/gap/pull/2260</Link></URL>).
</Item>
<Item>
Fix several potential (albeit rare) crashes related to garbage collection
(<URL><LinkText>&Hash;2321</LinkText><Link>https://github.com/gap-system/gap/pull/2321</Link></URL>,
<URL><LinkText>&Hash;2313</LinkText><Link>https://github.com/gap-system/gap/pull/2313</Link></URL>,
<URL><LinkText>&Hash;2320</LinkText><Link>https://github.com/gap-system/gap/pull/2320</Link></URL>).
</Item>
</List>


Removed or obsolete functionality:
<List>
<Item>
Make <C>SetUserPreferences</C> obsolete 
(use <Ref BookName="ref" Func="SetUserPreference"/> instead)
(<URL><LinkText>&Hash;512</LinkText><Link>https://github.com/gap-system/gap/pull/512</Link></URL>)
</Item>
<Item>
Remove undocumented <C>NameIsomorphismClass</C>
(<URL><LinkText>&Hash;597</LinkText><Link>https://github.com/gap-system/gap/pull/597</Link></URL>)
</Item>
<Item>
Remove unused code for rational classes of permutation groups
(<URL><LinkText>&Hash;886</LinkText><Link>https://github.com/gap-system/gap/pull/886</Link></URL>)
</Item>
<Item>
Remove unused and undocumented <C>Randomizer</C> and <C>CheapRandomizer</C>
(<URL><LinkText>&Hash;1113</LinkText><Link>https://github.com/gap-system/gap/pull/1113</Link></URL>)
</Item>
<Item>
Remove <File>install-tools.sh</File> script and documentation mentioning it
(<URL><LinkText>&Hash;1305</LinkText><Link>https://github.com/gap-system/gap/pull/1305</Link></URL>)
</Item>
<Item>
Withdraw <C>CallWithTimeout</C> and <C>CallWithTimeoutList</C>
(<URL><LinkText>&Hash;1324</LinkText><Link>https://github.com/gap-system/gap/pull/1324</Link></URL>)
</Item>
<Item>
Make <C>RecFields</C> obsolete
(use <Ref BookName="ref" Attr="RecNames"/> instead)
(<URL><LinkText>&Hash;1331</LinkText><Link>https://github.com/gap-system/gap/pull/1331</Link></URL>)
</Item>
<Item>
Remove undocumented <C>SuPeRfail</C> and <C>READ_COMMAND</C>
(<URL><LinkText>&Hash;1374</LinkText><Link>https://github.com/gap-system/gap/pull/1374</Link></URL>)
</Item>
<Item>
Remove unused <File>oldmatint.gi</File> (old methods for functions
that compute Hermite and Smith normal forms of integer matrices)
(<URL><LinkText>&Hash;1765</LinkText><Link>https://github.com/gap-system/gap/pull/1765</Link></URL>)
</Item>
<Item>
Make <C>TRANSDEGREES</C> obsolete
(<URL><LinkText>&Hash;1852</LinkText><Link>https://github.com/gap-system/gap/pull/1852</Link></URL>)
</Item>
</List>

</Subsection>

<Subsection Label="HPC-GAP-WIP"> 
<Heading>&HPCGAP;</Heading>

&GAP; includes experimental code to support multithreaded programming in &GAP;,
dubbed &HPCGAP; (where HPC stands for "high performance computing"). &GAP; and
&HPCGAP; codebases diverged during the project, and we are currently working
on unifying the codebases and incorporating the &HPCGAP; code back into the
mainstream &GAP; versions.
<P/>

This is work in progress, and &HPCGAP; as it is included with &GAP; right now
still suffers from various limitations and problems, which we are actively
working on to resolve. However, including it with &GAP; (disabled by default)
considerably simplifies development of &HPCGAP;. It also means that you can
very easily get a (rough!) sneak peak of &HPCGAP;. It comes together with the
new manual book called "&HPCGAP; Reference Manual" and located in the `doc/hpc`
directory.
<P/>

Users interested in experimenting with shared memory parallel programming in
&GAP; can build &HPCGAP; by following the instructions from
<URL>https://github.com/gap-system/gap/wiki/Building-HPC-GAP</URL>. While it is possible
to build &HPCGAP; from a release version of &GAP; you downloaded from the &GAP;
website, due to the ongoing development of &HPCGAP;, we recommend that you
instead build &HPCGAP; from the latest development version available in the
&GAP; repository at GitHub, i.e. <URL>https://github.com/gap-system/gap</URL>.

</Subsection>


<Subsection Label="New and updated packages since GAP 4.8.10"> 
<Heading>New and updated packages since &GAP; 4.8.10</Heading>

There were 132 packages redistributed together with &GAP; 4.8.10.
The &GAP; 4.9.1 distribution includes 134 packages, including numerous
updates of previously redistributed packages, and some major changes
outlined below.
<P/>

The libraries of small, primitive and transitive groups which previously
were an integral part of &GAP; were split into three separate packages
<URL Text="PrimgGrp">http://gap-packages.github.io/primgrp/</URL>,
<URL Text="SmallGrp">https://gap-packages.github.io/smallgrp/</URL> and
<URL Text="TransGrp">http://www.math.colostate.edu/~hulpke/transgrp/</URL>:
<List>
<Item>
The <Package>PrimGrp</Package> package by Alexander Hulpke, Colva M. Roney-Dougal
and Christopher Russell provides the library of primitive permutation
groups which includes, up to permutation isomorphism (i.e., up to conjugacy
in the corresponding symmetric group), all primitive permutation groups of
degree &lt; 4096.
</Item>
<Item>
The <Package>SmallGrp</Package> package by Bettina Eick, Hans Ulrich Besche and
Eamonn O’Brien provides the library of groups of certain <Q>small</Q>
orders. The groups are sorted by their orders and they are listed up to
isomorphism; that is, for each of the available orders a complete and
irredundant list of isomorphism type representatives of groups is given.
</Item>
<Item>
The <Package>TransGrp</Package> package by Alexander Hulpke provides
the library of transitive groups, with an optional download of the
library of transitive groups of degree 32.
</Item>
</List>
For backwards compatibility, these are required packages in &GAP; 4.9 (i.e.,
&GAP; will not start without them). We plan to change this for &GAP; 4.10
(see <URL><LinkText>&Hash;2434</LinkText><Link>https://github.com/gap-system/gap/pull/2434</Link></URL>),
once all packages which currently implicitly rely on these
new packages had time to add explicit dependencies on them
(<URL><LinkText>&Hash;1650</LinkText><Link>https://github.com/gap-system/gap/pull/1650</Link></URL>,
<URL><LinkText>&Hash;1714</LinkText><Link>https://github.com/gap-system/gap/pull/1714</Link></URL>).
<P/>

The new <Package>ZeroMQInterface</Package> package by Markus Pfeiffer
and Reimer Behrends has been added for the redistribution. It
provides both low-level bindings as well as some higher level interfaces
for the <URL Text="ZeroMQ">http://zeromq.org/</URL> message passing
library for &GAP; and &HPCGAP; enabling lightweight distributed
computation.
<P/>

The <Package>HAPprime</Package> package by Paul Smith is no longer 
redistributed with &GAP;. Part of the code has been incorporated into
the <Package>HAP</Package> package. Its source code repository, containing
the code of the last distributed version, can still be found at
<URL>https://github.com/gap-packages/happrime</URL>.
<P/>

Also, the <Package>ParGAP</Package> package by Gene Cooperman is no longer
redistributed with &GAP; because it no longer can be compiled with &GAP; 4.9
(see <URL Text="this announcement">https://mail.gap-system.org/pipermail/gap/2018-March/001082.html</URL>).
Its source code repository, containing the code of the last distributed
version, plus some first fixes needed for compatibility for GAP 4.9, can still
be found at <URL>https://github.com/gap-packages/pargap</URL>. If somebody
is interested in repairing this package and taking over its maintenance,
so that it can be distributed again, please contact the &GAP; team.

</Subsection>

</Section>

<Section Label="gap492">
<Heading>&GAP; 4.9.2 (July 2018)</Heading>

<Subsection Label="Changes in the core GAP system introduced in GAP 4.9.2">
<Heading>Changes in the core &GAP; system introduced in &GAP; 4.9.2</Heading>

Fixed bugs that could lead to break loops:
<List>
<Item>
Fixed a bug in iterating over an empty cartesian product
(<URL><LinkText>&Hash;2421</LinkText><Link>https://github.com/gap-system/gap/pull/2421</Link></URL>).
[Reported by @isadofschi]
</Item>
</List>

Fixed bugs that could lead to crashes:
<List>
<Item>
Fixed a crash after entering <C>return;</C> in a <Q>method not found</Q> break loop
(<URL><LinkText>&Hash;2449</LinkText><Link>https://github.com/gap-system/gap/pull/2449</Link></URL>).
</Item>
<Item>
Fixed a crash when an error occurs and
<Ref BookName="ref" Oper="OutputLogTo" Label="for streams"/>
points to a stream which internally uses another stream
(<URL><LinkText>&Hash;2596</LinkText><Link>https://github.com/gap-system/gap/pull/2596</Link></URL>).
</Item>
</List>

Fixed bugs that could lead to incorrect results:
<List>
<Item>
Fixed a bug in computing maximal subgroups, which broke some other
calculations, in particular, computing intermediate subgroups.
(<URL><LinkText>&Hash;2488</LinkText><Link>https://github.com/gap-system/gap/pull/2488</Link></URL>).
[Reported by Seyed Hassan Alavi]
</Item>
</List>

Other fixed bugs and further improvements:
<List>
<Item>
Profiling now correctly handles calls to <C>longjmp</C> and allows to generate
profiles using version 2.0.1 of the <Package>Profiling</Package> package
(<URL><LinkText>&Hash;2444</LinkText><Link>https://github.com/gap-system/gap/pull/2444</Link></URL>).
</Item>
<Item>
The <File>bin/gap.sh</File> script now respects the <C>GAP_DIR</C> environment variable
(<URL><LinkText>&Hash;2465</LinkText><Link>https://github.com/gap-system/gap/pull/2465</Link></URL>).
[Contributed by RussWoodroofe]
</Item>
<Item>
The <File>bin/BuildPackages.sh</File> script now properly builds binaries for
the <Package>simpcomp</Package> package
(<URL><LinkText>&Hash;2475</LinkText><Link>https://github.com/gap-system/gap/pull/2475</Link></URL>).
</Item>
<Item>
Fixed a bug in restoring a workspace, which prevented &GAP; from saving
the history if a workspace was loaded during startup
(<URL><LinkText>&Hash;2578</LinkText><Link>https://github.com/gap-system/gap/pull/2578</Link></URL>).
</Item>


</List>


</Subsection>

<Subsection Label="New and updated packages since GAP 4.9.1">
<Heading>New and updated packages since &GAP; 4.9.1</Heading>

This release contains updated versions of 22 packages
from &GAP; 4.9.1 distribution. Additionally, it has three new packages.
The new <Package>JupyterKernel</Package> package by Markus Pfeiffer provides
a so-called <E>kernel</E> for the Jupyter interactive document system
(<URL>https://jupyter.org/</URL>). This package requires Jupyter to be
installed on your system (see <URL>https://jupyter.org/install</URL>
for instructions). It also requires &GAP; packages <Package>IO</Package>,
<Package>ZeroMQInterface</Package>, <Package>json</Package>, and also two
new packages by Markus Pfeiffer called <Package>crypting</Package> and
<Package>uuid</Package>, all included into &GAP; 4.9.2 distribution.
The <Package>JupyterKernel</Package> package is not yet usable on Windows.

</Subsection>

</Section>


<Section Label="gap493">
<Heading>&GAP; 4.9.3 (September 2018)</Heading>

<Subsection Label="Changes in the core GAP system introduced in GAP 4.9.3">
<Heading>Changes in the core &GAP; system introduced in &GAP; 4.9.3</Heading>

Fixed bugs that could lead to break loops:
<List>
<Item>
Fixed a regression in <Ref Oper="HighestWeightModule" BookName="ref"/>
caused by changes in sort functions introduced in &GAP; 4.9 release
(<URL><LinkText>&Hash;2617</LinkText><Link>https://github.com/gap-system/gap/pull/2617</Link></URL>).
</Item>
</List>

Other fixed bugs and further improvements:
<List>
<Item>
Fixed a compile time assertion that caused compiler error on some systems
(<URL><LinkText>&Hash;2691</LinkText><Link>https://github.com/gap-system/gap/pull/2691</Link></URL>).
</Item>
</List>

</Subsection>

<Subsection Label="New and updated packages since GAP 4.9.2">
<Heading>New and updated packages since &GAP; 4.9.2</Heading>

This release contains updated versions of 18 packages
from &GAP; 4.9.2 distribution. Additionally, it has three new packages:
<List>
<Item>
The <Package>curlInterface</Package> package by Christopher Jefferson
and Michael Torpey, which provides a simple wrapper around
<Package>libcurl</Package> library (<URL>https://curl.haxx.se/</URL>)
to allow downloading files over http, ftp and https protocols.
</Item>
<Item>
The <Package>datastructures</Package> package by
Markus Pfeiffer, Max Horn, Christopher Jefferson and Steve Linton,
which aims at providing standard datastructures, consolidating
existing code and improving on it, in particular in view of &HPCGAP;.
</Item>
<Item>
The <Package>DeepThought</Package> package by Nina Wagner and Max Horn,
which provides functionality for computations in finitely generated
nilpotent groups given by a suitable presentation using Deep Thought
polynomials.
</Item>
</List>

</Subsection>

</Section>

</Chapter>