chap5.txt

  
  5 Changes between GAP 4.4 and GAP 4.5
  
  This  chapter  lists most important changes between GAP 4.4.12 and the first
  public  release  of  GAP  4.5. It also contains information about subsequent
  update  releases for GAP 4.5. It is not meant to serve as a complete account
  on  all improvements; instead, it should be viewed as an introduction to GAP
  4.5, accompanying its release announcement.
  
  
  5.1 Changes in the core GAP system introduced in GAP 4.5
  
  In this section we list most important new features and bugfixes in the core
  system  introduced  in  GAP  4.5.  For  the list of changes in the interface
  between  the  core system and packages as well as for an overview of new and
  updated packages, see Section 5.2.
  
  
  5.1-1 Improved functionality
  
  Performance improvements:
  
      The  GAP  kernel  now  uses  GMP  (GNU  multiple  precision arithmetic
        library, http://gmplib.org/) for faster large integer arithmetic.
  
      Improved performance for records with large number of components.
  
      Speedup of hash tables implementation at the GAP library level.
  
      MemoryUsage  (Reference:  MemoryUsage)  is now much more efficient, in
        particular for large objects.
  
      Speedups   in   the   computation   of  low  index  subgroups,  Tietze
        transformations,  calculating  high  powers  of  matrices  over finite
        fields, Factorial (Reference: Factorial), etc.
  
  New and improved kernel functionality:
  
      By  default,  the  GAP  kernel  compiles  with  the  GMP  and readline
        libraries.  The GMP library is supplied with GAP and we recommend that
        you use the version we supply. There are some problems with some other
        versions.  It  is  also  possible  to  compile the GAP kernel with the
        system  GMP  if  your  system  has  it.  The  readline library must be
        installed on your system in advance to be used with GAP.
  
      Floating  point  literals  are  now  supported in the GAP language, so
        that,  floating  point  numbers can be entered in GAP expressions in a
        natural  way.  Support  for  floats  is  now  properly documented, see
        'Reference: Floats'. GAP has an interface using which packages may add
        new floating point implementations and integrate them with the parser.
        In  particular,  we  expect  that  there  will  soon be a package that
        implements arbitrary precision floating point arithmetic.
  
      The Mersenne twister random number generator has been made independent
        of  endianness,  so  that  random seeds can now be transferred between
        architectures. See 'Reference: GlobalMersenneTwister' for details.
  
      Defaults  for -m and -o options have been increased. Changes have been
        made  to the way that GAP obtains memory from the Operating System, to
        make  GAP  more  compatible with C libraries. A new -s option has been
        introduced  to  control or turn off the new behaviour, see 'Reference:
        Command Line Options'.
  
      The  filename  and  lines  from  which  a function was read can now be
        recovered  using FilenameFunc (Reference: FilenameFunc), StartlineFunc
        (Reference:  StartlineFunc)  and EndlineFunc (Reference: EndlineFunc).
        This  allows  you,  for  example,  to  implement  a  function  such as
        PageSource  (Reference:  PageSource)  to  show the file containing the
        source  code  of  a  function  or  a  method  in  a  pager,  see Pager
        (Reference: Pager).
  
      CallFuncList  (Reference:  CallFuncList) was made into an operation so
        that  it can be used to define behaviour of a non-function when called
        as a function.
  
      Improvements to the cyclotomic number arithmetic for fields with large
        conductors.
  
      Better and more flexible viewing of some large objects.
  
      Opportunity   to   interrupt   some  long  kernel  computations,  e.g.
        multiplication   of   compressed   matrices,  intercepting  Ctrl-C  in
        designated  places  in  the  kernel  code by means of a special kernel
        function for that purpose.
  
      ELM_LIST  now  allows you to install methods where the second argument
        is NOT a positive integer.
  
      Kernel  function  DirectoryContents  (Reference: DirectoryContents) to
        get the list of names of files and subdirectories in a directory.
  
      Kernel  functions  for  Kronecker  product of compressed matrices, see
        KroneckerProduct (Reference: KroneckerProduct).
  
  New and improved library functionality:
  
      Extensions of data libraries:
  
            Functions   and  iterators  are  now  available  to  create  and
              enumerate  simple  groups  by  their  order  up  to isomorphism:
              SimpleGroup     (Reference:    SimpleGroup),    SmallSimpleGroup
              (Reference:  SmallSimpleGroup), SimpleGroupsIterator (Reference:
              SimpleGroupsIterator)     and     AllSmallNonabelianSimpleGroups
              (Reference: AllSmallNonabelianSimpleGroups).
  
            See  also  packages  CTblLib,  IRREDSOL  and Smallsemi listed in
              Section 5.2-2.
  
      Many  more  methods  are now available for the built-in floating point
        numbers, see 'Reference: Floats'.
  
      The  bound  for  the  proper  primality test in IsPrimeInt (Reference:
        IsPrimeInt) increased up to 10^18.
  
      Improved   code   for   determining   transversal   and  double  coset
        representatives in large groups.
  
      Improvements in Normalizer (Reference: Normalizer) for S_n.
  
      Smith normal form of a matrix may be computed over arbitrary euclidean
        rings, see NormalFormIntMat (Reference: NormalFormIntMat).
  
      Improved  algorithms  to determine the subgroup lattice of a group, as
        well    as    the    function    DotFileLatticeSubgroups   (Reference:
        DotFileLatticeSubgroups) to save the lattice structure in .dot file to
        view it e.g. with GraphViz.
  
      Special  teaching  mode which simplifies some output and provides more
        basic functionality, see 'Reference: Teaching Mode'.
  
      Functionality  specific  for  use  in  undergraduate  abstract algebra
        courses,  e.g.  checksums  ('Reference: Check Digits'); string/integer
        list  conversion;  rings  of  small orders; the function SetNameObject
        (Reference:  SetNameObject)  to set display names for objects for more
        informative  examples,  e.g.  constructing  groups from named objects,
        such as, for example, R90 for a 90-degree rotation).
  
      Functions    DirectoryDesktop    (Reference:   DirectoryDesktop)   and
        DirectoryHome  (Reference: DirectoryHome) which provide uniform access
        to default directories under Windows, Mac OS X and Unix.
  
      Improved methods for hashing when computing orbits.
  
      Functionality to call external binaries under Windows.
  
      Symplectic  groups  over  residue  class  rings,  see  SymplecticGroup
        (Reference: SymplecticGroup).
  
      Basic version of the simplex algorithm for matrices.
  
      New  functions,  operations  and attributes: PrimeDivisors (Reference:
        PrimeDivisors),    Shuffle    (Reference:    Shuffle)    for    lists,
        IteratorOfPartitions         (Reference:        IteratorOfPartitions),
        IteratorOfCombinations       (Reference:      IteratorOfCombinations),
        EnumeratorOfCombinations   (Reference:  EnumeratorOfCombinations)  and
        others.
  
      The  behaviour  of  Info  (Reference:  Info)  statements  can  now  be
        configured  per  info class, this applies to the way the arguments are
        printed and to the output stream, see 'Reference: Info Functions'.
  
      New  function  Test  (Reference:  Test)  which  is a more flexible and
        informative substitute of ReadTest operation.
  
      ConnectGroupAndCharacterTable  is  replaced  by  more  robust function
        CharacterTableWithStoredGroup                              (Reference:
        CharacterTableWithStoredGroup).
  
  Many problems in GAP have have been fixed, among them the following:
  
      Polynomial  factorisation  over rationals could miss factors of degree
        greater  than deg(f)/2 if they have very small coefficients, while the
        cofactor has large coefficients.
  
      IntermediateSubgroups  (Reference:  IntermediateSubgroups) called on a
        group  and  a  normal  subgroup  did  not  properly  calculate maximal
        inclusion relationships.
  
      CentreOfCharacter       (Reference:       CentreOfCharacter)       and
        ClassPositionsOfCentre   (Reference:   ClassPositionsOfCentre   for  a
        character)  called  for  a  group character could return a perhaps too
        large result.
  
      Trace (Reference: Traces of field elements and matrices) called for an
        element  of  a  finite  field that was created with AlgebraicExtension
        (Reference: AlgebraicExtension) ran into an error.
  
      IrreducibleRepresentationsDixon                            (Reference:
        IrreducibleRepresentationsDixon)  did  not  accept  a  list  with  one
        character as a second argument.
  
      Composing  a  homomorphism  from  a  permutation  group  to a finitely
        presented group with another homomorphism could give wrong results.
  
      For  certain arguments, the function EU (Reference: EU) returned wrong
        results.
  
      In  the  table  of  marks of cyclic groups, NormalizersTom (Reference:
        NormalizersTom) value was wrong.
  
      The function PermChars (Reference: PermChars) 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.
  
      GAP crashed when the intersection of ranges became empty.
  
      IsPSL,     and     in     turn     StructureDescription    (Reference:
        StructureDescription),  erroneously  recognised  non-PSL groups of the
        right order as PSL.
  
      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.
  
      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.
  
      Constant   polynomials  were  not  recognised  as  univariate  in  any
        variable.
  
      The kernel recursion depth counter was not reset properly when running
        into many break loops.
  
      GAP  did  not  behave  well  when  printing  of  a  (large) object was
        interrupted with Ctrl-C. Now the object is no longer corrupted and the
        indentation level is reset.
  
  Potentially incompatible changes:
  
      The    zero    polynomial    now    has    degree    -infinity,    see
        DegreeOfLaurentPolynomial (Reference: DegreeOfLaurentPolynomial).
  
      Multiple  unary + or - signs are no longer allowed (to avoid confusion
        with increment/decrement operators from other programming languages).
  
      Due to changes to improve the performance of records with large number
        of  components,  the  ordering of record components in View'ed records
        has changed.
  
      Due  to  improvements  for vectors over finite fields, certain objects
        have  more  limitations on changing their base field. For example, one
        can  not  create  a  compressed  matrix  over GF(2) and then assign an
        element of GF(4) to one of its entries.
  
  No longer supported:
  
      Completion files mechanism.
  
      GAP 3 compatibility mode.
  
  In  addition,  we  no longer recommend using the GAP compiler gac to compile
  GAP  code  to  C, and may withdraw it in future releases. Compiling GAP code
  only   ever  gave  a  substantial  speedup  for  rather  specific  types  of
  calculation,  and  much more benefit can usually be achieved quite easily by
  writing  a  small  number  of  key  functions in C and loading them into the
  kernel as described in LoadDynamicModule (Reference: LoadDynamicModule). The
  gac  script  will  remain  available  as  a convenient way of compiling such
  kernel modules from C.
  
  Also,   the   following   functions   and  operations  were  made  obsolete:
  AffineOperation,         AffineOperationLayer,         FactorCosetOperation,
  DisplayRevision, ProductPol, TeXObj, LaTeXObj.
  
  
  5.1-2 Changes in distribution formats
  
  The  GAP 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
  TomLib  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  tools archive is now included as an archive in the etc directory. To
  unpack and install the archive, user the script etc/install-tools.sh.
  
  We  no  longer  distribute separate bugfix archives when the core GAP system
  changes,  or  updated  packages  archives  when  a  redistributed package is
  updated.  Instead,  the  single  GAP  source  distribution  archive  will be
  labelled by the version of the core GAP system and also by a timestamp. This
  archive  contains  the  core  system and the stable versions of the relevant
  packages  on  that  date. To upgrade, you simply replace the whole directory
  containing the GAP installation, and rebuild binaries for the GAP kernel and
  packages.   For   new  versions  of  packages,  we  will  also  continue  to
  redistribute  individual package archives so it will be possible to update a
  single package without changing the rest of the GAP installation.
  
  Furthermore,  by default GAP will now automatically read a user-specific GAP
  root  directory (unless GAP is called with the -r 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  5.1-3  below  for  more details). Private
  packages can also be installed in this directory for the same reason.
  
  There  are  some  changes  in  archive formats used for the distribution: we
  continue  to  provide .tar.gz, .tar.bz2 and -win.zip archives. We have added
  .zip, and stopped providing .zoo 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.
  
  With  the release of GAP 4.5, we also encourage more users to take advantage
  of  the  increasingly  mature  binary distributions which are now available.
  These include:
  
      The binary rsync distribution for GAP on Linux PCs with i686 or x86_64
        compatible     processors    provided    by    Frank    Lübeck,    see
        http://www.math.rwth-aachen.de/~Frank.Luebeck/gap/rsync.
  
      BOB,  a  tool for Linux and Mac OS X to download and build GAP and its
        packages     from     source     provided     by     M.    Neunhöffer:
        http://www-groups.mcs.st-and.ac.uk/~neunhoef/Computer/Software/Gap/bob.html.
  
      The  GAP  installer  for  Windows  provided  by  Alexander  Konovalov:
        https://www.gap-system.org/ukrgap/wininst/.
  
  In the near future, we also hope to have a binary distribution for Mac OS X.
  
  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  Example  package  documents
  technical requirements for packages, many of which are checked automatically
  by  our  systems.  This will allow us to check the compatibility of packages
  with  the  system  and with other packages more thoroughly before publishing
  them on the GAP website.
  
  
  5.1-3 Improvements to the user interface
  
  By  default,  GAP now uses the readline 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 'Reference: Editing using the readline library'.
  
  We have extended facilities for user interface customisation. By default GAP
  automatically scans a user specific GAP root directory (unless GAP is called
  with the -r option). The name of this user specific directory depends on the
  operating system and is contained in GAPInfo.UserGapRoot. This directory can
  be  used  to  tell  GAP  about personal preferences, to load some additional
  code,  to  install  additional packages, or to overwrite some GAP files, see
  'Reference:  GAP  Root  Directories'. Instead of a single .gaprc file we now
  use  more  flexible setup based on two files: gap.ini which is read early in
  the  startup process, and gaprc which is read after the startup process, but
  before  the  first  input file given on the command line. These files may be
  located in the user specific GAP root directory GAPInfo.UserGapRoot which by
  default  is  the  first  GAP root directory, see 'Reference: The gap.ini and
  gaprc  files'.  For  compatibility,  the  .gaprc  file  is still read if the
  directory  GAPInfo.UserGapRoot  does  not  exist. See 'Reference: The former
  .gaprc file' for the instructions how to migrate your old setup.
  
  Furthermore, there are functions to deal with user preferences, for example,
  to  specify  how  GAP's  online help is shown or whether the coloured prompt
  should  be  used.  Calls  to  set  user preferences may appear in the user's
  gap.ini file, as explained in 'Reference: Configuring User preferences'.
  
  In  the  Windows  version,  we  include  a  new  shell which uses the mintty
  terminal in addition to the two previously used shells (Windows command line
  and RXVT). The mintty shell is now recommended. It supports Unicode encoding
  and  has flexible configurations options. Also, GAP under Windows now starts
  in  the %HOMEDRIVE%%HOMEPATH% directory, which is the user's home directory.
  Besides  this,  a larger workspace is now permitted without a need to modify
  the Windows registry.
  
  Other changes in the user interface include:
  
      the  command  line history is now implemented at the GAP level, it can
        be  stored  on  quitting  a GAP session and reread when starting a new
        session, see 'Reference: The command line history'.
  
      SetPrintFormattingStatus("stdout",false);  may  be  used to switch off
        the    automatic    line    breaking    in    terminal   output,   see
        SetPrintFormattingStatus (Reference: SetPrintFormattingStatus).
  
      GAP  supports terminals with up to 4096 columns (extendable at compile
        time).
  
      Directories  in  -l  command-line option can now be specified starting
        with ~/, see 'Reference: Command Line Options'.
  
      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  UserPreference("MaxBitsIntView") to see the
        default value).
  
      The GAP banner has been made more compact and informative.
  
      SetHelpViewer  (Reference:  SetHelpViewer)  now  supports  the  Google
        Chrome browser.
  
      Multiple  matches  in the GAP online help are displayed via a function
        from the Browse package, which is loaded in the default configuration.
        This feature can be replaced by the known pager using the command
  
  SetUserPreference( "browse", "SelectHelpMatches", false );
  
  
  5.1-4 Better documentation
  
  The  main  GAP  manuals have been converted to the GAPDoc format provided by
  the    GAPDoc    package    by    Frank    Lübeck    and    Max   Neunhöffer
  (http://www.math.rwth-aachen.de/~Frank.Luebeck/GAPDoc).  This  documentation
  format  is  already used by many packages and is now recommended for all GAP
  documentation.
  
  Besides  improvements  to the documentation layout in all formats (text, PDF
  and  HTML),  the  new GAP manuals incorporate a large number of corrections,
  clarifications, additions and updated examples.
  
  We  now  provide  two  HTML versions of the manual, one of them with MathJax
  (http://www.mathjax.org) support for better display of mathematical symbols.
  Also, there are two PDF versions of the manual - a coloured and a monochrome
  one.
  
  Several separate manuals now became parts of the GAP Reference manual. Thus,
  now there are three main GAP manual books:
  
      GAP Tutorial
  
      GAP Reference manual
  
      GAP - Changes from Earlier Versions (this manual)
  
  Note  that  there is no index file combining these three manuals. Instead of
  that,  please  use  the  GAP  help system which will search all of these and
  about 100 package manuals.
  
  
  5.2 Packages in GAP 4.5
  
  Here  we  list  most important changes affecting packages and present new or
  essentially  changed  packages.  For the changes in the core GAP system, see
  Section 5.1.
  
  
  5.2-1 Interface between the core system and packages
  
  The  package  loading  mechanism  has  been improved. The most important new
  feature  is  that all dependencies are evaluated in advance and then used to
  determine  the  order  in  which  package files are read. This allows GAP to
  handle  cyclic  dependencies  as well as situations where package A requires
  package  B  to be loaded completely before any file of package A is read. To
  avoid  distortions  of  the  order in which packages will be loaded, package
  authors  are  strongly  discouraged  from  calling  LoadPackage  (Reference:
  LoadPackage)         and         TestPackageAvailability         (Reference:
  TestPackageAvailability)  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 IsPackageMarkedForLoading (Reference:
  IsPackageMarkedForLoading).  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 DisplayPackageLoadingLog
  (Reference:   DisplayPackageLoadingLog)   and   the   rest  of  the  Chapter
  'Reference:  Using  GAP  Packages' which documents how to use GAP packages),
  and   package  authors  are  very  much  encouraged  to  use  these  logging
  facilities.
  
  In  GAP  4.4 certain packages were marked as autoloaded and would be loaded,
  if  present,  when  GAP  started up. In GAP 4.5, this notion is divided into
  three.  Certain packages are recorded as needed by the GAP system and others
  as  suggested,  in  the  same  way  that  packages may need or suggest other
  packages. If a needed package is not loadable, GAP will not start. Currently
  only  GAPDoc  is  needed.  If  a  suggested  package is loadable, it will be
  loaded.  Typically  these  are  packages  which  install  better methods for
  Operations and Objects already present in GAP. Finally, the user preferences
  mechanism  can  be used to specify additional packages that should be loaded
  if  possible. By default this includes most packages that were autoloaded in
  GAP 4.4.12, see ShowUserPreferences (Reference: ShowUserPreferences).
  
  GAP  packages  may now use local namespaces to avoid name clashes for global
  variables   introduced  in  other  packages  or  in  the  GAP  library,  see
  'Reference: Namespaces for GAP packages'.
  
  All  guidance  on  how to develop a GAP package has been consolidated in the
  Example  package which also contains a checklist for upgrading a GAP package
  to GAP 4.5, see 'Example: Guidelines for Writing a GAP Package'.
  
  
  5.2-2 New and updated packages since GAP 4.4.12
  
  At   the  time  of  the  release  of  GAP  4.4.12  there  were  75  packages
  redistributed  with  GAP  (including the TomLib which was distributed in the
  core GAP archive). The first public release of GAP 4.5 contains precisely 99
  packages.
  
  The  new  packages  that  have  been  added  to the redistribution since the
  release of GAP 4.4.12 are:
  
      Citrus  package  by J.D. Mitchell for computations with transformation
        semigroups  and  monoids  (this package is a replacement of the Monoid
        package).
  
      cvec  package by M. Neunhöffer, providing an implementation of compact
        vectors over finite fields.
  
      fwtree  package by B. Eick and T. Rossmann for computing trees related
        to some pro-p-groups of finite width.
  
      GBNP  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.
  
      genss  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.
  
      HAPprime  package  by  P.  Smith,  extending  the  HAP package with an
        implementation  of  memory-efficient algorithms for the calculation of
        resolutions of small prime-power groups.
  
      hecke  package  by  D.  Traytel,  providing  functions for calculating
        decomposition  matrices  of Hecke algebras of the symmetric groups and
        q-Schur  algebras  (this package is a port of the GAP 3 package Specht
        2.4 to GAP 4).
  
      Homalg  project  by M. Barakat, S. Gutsche, M. Lange-Hegermann et al.,
        containing the following packages for the homological algebra: homalg,
        ExamplesForHomalg,      Gauss,      GaussForHomalg,     GradedModules,
        GradedRingForHomalg, HomalgToCAS, IO_ForHomalg, LocalizeRingForHomalg,
        MatricesForHomalg,    Modules,    RingsForHomalg    and    SCO    (see
        http://homalg.math.rwth-aachen.de/).
  
      MapClass  package  by  A.  James,  K.  Magaard  and  S.  Shpectorov to
        calculate the mapping class group orbits for a given finite group.
  
      recogbase  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).
  
      recog  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 recogbase
        package  and  provides  a  collection  of methods for the constructive
        recognition  of groups (mostly intended for permutation groups, matrix
        groups and projective groups).
  
      SCSCP package by A. Konovalov and S. Linton, implementing the Symbolic
        Computation    Software    Composability    Protocol    (SCSCP,    see
        http://www.symbolic-computation.org/scscp)  for  GAP,  which  provides
        interfaces  to  link  a GAP instance with another copy of GAP or other
        SCSCP-compliant system running locally or remotely.
  
      simpcomp  package  by  F.  Effenberger  and J. Spreer for working with
        simplicial complexes.
  
      Smallsemi 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.
  
      SymbCompCC  package  by  D.  Feichtenschlager  for  computations  with
        parametrised presentations for finite p-groups of fixed coclass.
  
  Furthermore,  some  packages  have  been  upgraded  substantially  since the
  GAP 4.4.12 release:
  
      Alnuth 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.
  
      CTblLib  package  (the  GAP  Character Table Library) by T. Breuer has
        been  extended  by  many  new  character  tables, a few bugs have been
        fixed,  and  new  features have been added, for example concerning the
        relation  to  GAP's  group  libraries,  better  search facilities, and
        interactive overviews. For details, see the package manual.
  
      DESIGN package by L.H. Soicher:
  
            The  functions PointBlockIncidenceMatrix, ConcurrenceMatrix, and
              InformationMatrix   compute   matrices   associated  with  block
              designs.
  
            The  function BlockDesignEfficiency computes certain statistical
              efficiency measures of a 1-(v,k,r) design, using exact algebraic
              computation.
  
      Example  package  by  W. Nickel, G. Gamble and A. Konovalov has a more
        detailed  and  up-to-date  guidance  on  developing a GAP package, see
        'Example: Guidelines for Writing a GAP Package'.
  
      FR  package by L. Bartholdi now uses floating-point numbers to compute
        approximations  of  rational  maps  given  by  their group-theoretical
        description.
  
      The  GAPDoc  package  by  F. Lübeck and M. Neunhöffer provides various
        improvements, for example:
  
            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.
  
            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.
  
            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).
  
            The PDF version of the manuals uses better fonts.
  
            Of course, there are various improvements for authors of manuals
              as  well,  for  example  new  functions ExtractExamples (GAPDoc:
              ExtractExamples)   and  RunExamples  (GAPDoc:  RunExamples)  for
              automatic testing and correcting of manual examples.
  
      Gpd  package  by  E.J.  Moore  and C.D. Wensley has been substantially
        rewritten. The main extensions provide functions for:
  
            Subgroupoids  of  a direct product with complete graph groupoid,
              specified by a root group and choice of rays.
  
            Automorphisms  of  finite groupoids - by object permutations; by
              root group automorphisms; and by ray images.
  
            The  automorphism  group  of  a finite groupoid together with an
              isomorphism to a quotient of permutation groups.
  
            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 XMod package.
  
      GRAPE package by L.H. Soicher:
  
            With  much  help from A. Hulpke, the interface between GRAPE and
              dreadnaut is now done entirely in GAP code.
  
            A  32-bit  nauty/dreadnaut  binary for Windows (XP and later) is
              included  with  GRAPE,  so now GRAPE provides full functionality
              under Windows, with no installation necessary.
  
            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).
  
            The  GAP  code  and old standalone programs for the undocumented
              functions  Enum  and  EnumColadj  have  been  removed  as  their
              functionality  can  now largely be handled by current documented
              GAP and GRAPE functions.
  
      IO package by M. Neunhöffer:
  
            New build system to allow for more flexibility regarding the use
              of compiler options and adjusting to GAP 4.5.
  
            New functions to access time like IO_gettimeofday, IO_gmtime and
              IO_localtime.
  
            Some  parallel  skeletons  built  on  fork  like: ParListByFork,
              ParMapReduceByFork,         ParTakeFirstResultByFork         and
              ParWorkerFarmByFork.
  
            IOHub objects for automatic I/O multiplexing.
  
            New functions IO_gethostbyname and IO_getsockname.
  
      IRREDSOL  package  by  B.  Höfling  now covers all irreducible soluble
        subgroups   of  GL(n,q)  for  q^n  <  1000000  and  primitive  soluble
        permutation  groups  of  degree  <  1000000 (previously, the bound was
        65536).  It also has faster group recognition and adds a few omissions
        for GL(3,8) and GL(6,5).
  
      ParGAP 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 MPINU library which is
        still  supplied  with  the  package  (thanks to P. Smith for upgrading
        ParGAP build process).
  
      OpenMath  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
        SCSCP  package. Also, a third-party external library to support binary
        OpenMath  encoding  has  been replaced by a proper implementation made
        entirely in GAP.
  
      Orb package by J. Müller, M. Neunhöffer and F. Noeske:
  
        There have been numerous improvements to this package:
  
            A  new  fast implementation of AVL trees (balanced binary trees)
              in C.
  
            New  interface to hash table functionality and implementation in
              C for speedup.
  
            Some   new   hash   functions  for  various  object  types  like
              transformations.
  
            New function ORB_EstimateOrbitSize using the birthday paradox.
  
            Improved functionality for product replacer objects.
  
            New tree hash tables.
  
            New   functionality  to  compute  weak  and  strong  orbits  for
              semigroups and monoids.
  
            OrbitGraph for Orb orbits.
  
            Fast C kernel methods for the following functions:
  
              PermLeftQuoTransformationNC,                  MappingPermSetSet,
              MappingPermListList,        ImageSetOfTransformation,        and
              KernelOfTransformation.
  
            New build system to allow for more flexibility regarding the use
              of compiler options and to adjust to GAP 4.5.
  
      RCWA  package by S. Kohl among the new features and other improvements
        has the following:
  
            A   database   of   all   52394  groups  generated  by  3  class
              transpositions  of  ℤ  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 ℤ look like.
  
            More  routines  for investigating the action of an rcwa group on
              ℤ.  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 ℤ.
  
            Ability to deal with rcwa permutations of ℤ^2.
  
            Important  methods  have  been  made  more efficient in terms of
              runtime and memory consumption.
  
            The output has been improved. For example, rcwa permutations are
              now Display'ed in ASCII text resembling LaTeX output.
  
      The  XGAP  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 XGAP has been
        adjusted to GAP 4.5.
  
      Additionally,  some  packages with kernel modules or external binaries
        are  now  available  in  Windows.  The  -win.zip  archive  and the GAP
        installer  for  Windows  include  working  versions  of  the following
        packages: Browse, cvec, EDIM, GRAPE, IO and orb, which were previously
        unavailable for Windows users.
  
  Finally, the following packages are withdrawn:
  
      IF 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 SCSCP package by A. Konovalov and S.
        Linton.
  
      Monoid  package  by J. Mitchell is superseded by the Citrus package by
        the same author.
  
      NQL package by R. Hartung has been withdrawn by the author.
  
  
  5.3 GAP 4.5.5 (July 2012)
  
  Fixed bugs which could lead to crashes:
  
      For  small  primes  (compact  fields)  ZmodnZObj(r,p)  now returns the
        corresponding FFE to avoid crashes when compacting matrices. [Reported
        by Ignat Soroko]
  
  Other fixed bugs:
  
      Fixed  a bug in CommutatorSubgroup (Reference: CommutatorSubgroup) for
        fp  groups  causing  infinite  recursion, which could, for example, be
        triggered by computing automorphism groups.
  
      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]
  
      Computing  high  powers  of matrices ran into an error for matrices in
        the  format  of  the cvec package. Now the library function also works
        with these matrices. [reported by Klaus Lux]
  
      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 ANUPQ and nq
        packages   to   compute  group  quotients  via  an  external  program.
        Previously,  on  Mac  OS X this could be done precisely 128 times, and
        then  an  error  would  occur.  That  is,  one  could e.g. compute 128
        nilpotent quotients, and then had to restart GAP to compute more. This
        also  affected other systems, such as OpenBSD, where it now also works
        correctly.
  
      On Mac OS X, using GAP compiled against GNU readline 6.2, pasting text
        into  the  terminal  session  would result in this text appearing very
        slowly,  with  a 0.1 sec delay between each 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  rl_event_hook only if OnCharReadHookActive is
        set.
  
      ShowUserPreferences  (Reference: ShowUserPreferences) ran into a break
        loop  in  case  of  several  undeclared user preferences. [Reported by
        James Mitchell]
  
      GAP    did    not    start    correctly   if   the   user   preference
        "InfoPackageLoadingLevel" was set to a number >= 3. The reason is that
        PrintFormattedString  was  called before it was installed. The current
        fix is a temporary solution.
  
      The "hints" member of TypOutputFile used to contain 3*100 entries, yet
        addLineBreakHint  would  write  entries with index up to and including
        3*99+3=300,   leading   to  a  buffer  overflow.  This  would  end  up
        overwriting  the  "stream"  member  with -1. Fixed by incrementing the
        size of "hints" to 301. [Reported by Jakob Kroeker]
  
      The  function  IsDocumentedWord  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.
  
      On  Windows, an error occurred if one tried to use the default Windows
        browser    as   a   help   viewer   (see   SetHelpViewer   (Reference:
        SetHelpViewer)).  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.
  
  Improved functionality:
  
      WriteGapIniFile  (Reference:  WriteGapIniFile) on Windows now produces
        the gap.ini file with Windows style line breaks. Also, an info message
        is  now printed if an existing gap.ini file was moved to a backup file
        gap.ini.bak.
  
      The CTblLib and TomLib packages are removed from the list of suggested
        packages  of  the  core  part  of  GAP.  Instead they are added to the
        default  list  of the user preference "PackagesToLoad". This way it is
        possible  to configure GAP to not load these packages via changing the
        default value of "PackagesToLoad".
  
      The  conjugacy  test  in  S_n for intransitive subgroups was improved.
        This  deals  with  inefficiency  issue  in the case reported by Stefan
        Kohl.
  
      Added   InstallAndCallPostRestore  to  lib/system.g  and  call  it  in
        lib/init.g  instead of CallAndInstallPostRestore for the function that
        reads  the  files  listed  in GAP command line. This fixes the problem
        reported    by   Yevgen   Muntyan   when   SaveWorkspace   (Reference:
        SaveWorkspace)  was used in a file listed in GAP command line (before,
        according    to    the    documentation,   SaveWorkspace   (Reference:
        SaveWorkspace) was only allowed at the main GAP prompt).
  
      There   is   now   a   new   user   preference  PackagesToIgnore,  see
        SetUserPreference  (Reference:  SetUserPreference). 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
        LoadPackage  (Reference:  LoadPackage).  This preference is useful for
        testing purposes if one wants to run some code without loading certain
        packages.
  
  
  5.4 GAP 4.5.6 (September 2012)
  
  Improved functionality:
  
      The argument of SaveWorkspace (Reference: SaveWorkspace) can now start
        with ~/ which is expanded to the users home directory.
  
      Added    the   method   for   Iterator   (Reference:   Iterator)   for
        PositiveIntegers  (Reference:  PositiveIntegers). [Suggested by Attila
        Egri-Nagy].
  
      Changed   kernel  tables  such  that  list  access  functionality  for
        T_SINGULAR objects can be installed by methods at the GAP level.
  
      In  case  of  saved  history,  UP arrow after starting GAP yields last
        stored  line.  The  user  preference  HistoryMaxLines is now used when
        storing   and   saving   history  (see  SetUserPreference  (Reference:
        SetUserPreference)).
  
  Fixed bugs which could lead to crashes:
  
      A  crash  occuring  during  garbage  collection  following  a  call to
        AClosVec for a GF(2) code. [Reported by Volker Braun]
  
      A  crash when parsing certain syntactically invalid code. [Reported by
        multiple users]
  
      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]
  
      Fixed a bug in the kernel code for floats that caused a crash on SPARC
        Solaris in 32-bit mode. [Reported by Volker Braun]
  
  Other fixed bugs:
  
      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]
  
      An  old  variable was used in assertion, causing errors in a debugging
        compilation. [Reported by Volker Braun]
  
      The  environment  variable  PAGER is now correctly interpreted when it
        contains  the  full  path  to  the  pager program. Furthermore, if the
        external pager less is found from the environment it is made sure that
        the  option  -r  is  used  (same  for  more -f). [Reported by Benjamin
        Lorenz]
  
      Fixed a bug in PermliftSeries. [Reported by Aiichi Yamasaki]
  
      Fixed discarder function in lattice computation to distinguish general
        and zuppo discarder. [Reported by Leonard Soicher]
  
      The  GL (Reference: GL for dimension and a ring) and SL (Reference: SL
        for  dimension  and  a  ring)  constructors  did  not correctly handle
        GL(filter,dim,ring).
  
      The names of two primitive groups of degree 64 were incorrect.
  
      The  \in  (Reference: \in operation for testing membership) 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 SeedFaithfulAction to influence how NiceMonomorphism (Reference:
        NiceMonomorphism) builds the nice monomorphims for a matrix groups.
  
      Wrong  PrintObj  (Reference:  PrintObj)  method  was  removed  to  fix
        delegations accordingly to 'Reference: View and Print'.
  
      Fixed a method for Coefficients (Reference: Coefficients) 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]
  
  Improved documentation:
  
      Removed    outdated    statements    from    the    documentation   of
        StructureDescription   (Reference:   StructureDescription)  which  now
        non-ambiguosly  states that StructureDescription 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.
  
      GAP  now  allows  overloading of a loaded help book by another one. In
        this  case,  only  a  warning  is printed and no error is raised. This
        makes sense if a book of a not loaded package is loaded in a workspace
        and  then  GAP  is  started  with  a  root  path that contains a newer
        version. [Reported by Sebastian Gutsche]
  
      Provided   a   better   description   of  user  preferences  mechanism
        ('Reference:  Configuring User preferences') and a hint to familiarise
        with  them using WriteGapIniFile (Reference: WriteGapIniFile) function
        to  create  a  file  which  contains  descriptions  of  all known user
        preferences  and  also  sets those user preferences which currently do
        not have their default value. One can then edit that file to customize
        (further) the user preferences for future GAP sessions.
  
  New packages added for the redistribution with GAP:
  
      AutoDoc   package   by  S.  Gutsche,  providing  tools  for  automated
        generation of GAPDoc manuals.
  
      Convex package by S. Gutsche, which provides structures and algorithms
        for convex geometry.
  
      PolymakeInterface  package  by T. Baechler and S. Gutsche, providing a
        link    to    the    callable   library   of   the   polymake   system
        (http://www.polymake.org).
  
      ToolsForHomalg   package   by   M.   Barakat,   S.   Gutsche   and  M.
        Lange-Hegermann,  which  provides some auxiliary functionality for the
        homalg project (http://homalg.math.rwth-aachen.de/).
  
  
  5.5 GAP 4.5.7 (December 2012)
  
  Fixed bugs which could lead to crashes:
  
      Closing  with  LogInputTo (or LogOutputTo) a logfile opened with LogTo
        (Reference:  LogTo) left the data structures corrupted, resulting in a
        crash.
  
      On  32-bit systems we can have long integers n such that Log2Int(n) is
        not  an  immediate  integer.  In  such  cases  Log2Int  gave  wrong or
        corrupted results which in turn could crash GAP, e.g., in ViewObj(n).
  
      Some   patterns  of  use  of  UpEnv  (Reference:  UpEnv)  and  DownEnv
        (Reference: DownEnv) were leading to a segfault.
  
  Other fixed bugs:
  
      Viewing  of  long negative integers was broken, because it went into a
        break loop.
  
      Division  by zero in ZmodnZ (Reference: ZmodnZ) (n not prime) produced
        invalid objects. [Reported by Mark Dickinson]
  
      Fixed   a  bug  in  determining  multiplicative  inverse  for  a  zero
        polynomial.
  
      Fixed      a      bug      causing      infinite      recursion     in
        NaturalHomomorphismByNormalSubgroup                        (Reference:
        NaturalHomomorphismByNormalSubgroup).
  
      A workaround was added to deal with a package method creating pcgs for
        permutation groups for which the entry permpcgsNormalSteps is missing.
  
      For a semigroup of associative words that is not the full semigroup of
        all  associative  words,  the  methods  for Size (Reference: Size) and
        IsTrivial  (Reference:  IsTrivial) called one another causing infinite
        recursion.
  
      The  64-bit  version  of  the  gac script produced wrong (>= 2^31) CRC
        values because of an integer conversion problem.
  
      It  was  not possible to compile GAP on some systems where HAVE_SELECT
        detects as false.
  
      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]
  
  New packages added for the redistribution with GAP:
  
      Float  package  by  L.  Bartholdi,  which  extends  GAP floating-point
        capabilities    by   providing   new   floating-point   handlers   for
        high-precision real, interval and complex arithmetic using MPFR, MPFI,
        MPC   or   CXSC   external   libraries.   It   also  contains  a  very
        high-performance  implementation  of  the LLL (Lenstra-Lenstra-Lovász)
        lattice reduction algorithm via the external library FPLLL.
  
      ToricVarieties  package  by S. Gutsche, which provides data structures
        to  handle  toric varieties by their commutative algebra structure and
        by their combinatorics.