  
  [1X9 [33X[0;0YChanges from Earlier Versions[133X[101X
  
  
  [1X9.1 [33X[0;0YEarlier Changes[133X[101X
  
  [33X[0;0YThe most important changes between [5XGAP[105X 4.2 and [5XGAP[105X 4.3 were:[133X
  
  [30X    [33X[0;6YThe performance of several routines has been substantially improved.[133X
  
  [30X    [33X[0;6YThe  functionality  in  the  areas of finitely presented groups, Schur
        covers and the calculation of representations has been extended.[133X
  
  [30X    [33X[0;6YThe  data  libraries  of  transitive  groups,  finite  integral matrix
        groups, character tables and tables of marks have been extended.[133X
  
  [30X    [33X[0;6YThe  Windows  installation  has been simplified for the case where you
        are installing [5XGAP[105X in its standard location.[133X
  
  [30X    [33X[0;6YMany bugs have been fixed.[133X
  
  [33X[0;0YThe most important changes between [5XGAP[105X 4.1 and [5XGAP[105X 4.2 were:[133X
  
  [30X    [33X[0;6YA  much  extended  and  improved  library  of  small groups as well as
        associated [2XIdGroup[102X ([14Xsmallgrp: IdGroup[114X) routines.[133X
  
  [30X    [33X[0;6YThe  primitive  groups  library  has been made more independent of the
        rest of [5XGAP[105X, some errors were corrected.[133X
  
  [30X    [33X[0;6YNew  (and  often  much  faster)  infrastructure for orbit computation,
        based on a general [21Xdictionary[121X abstraction.[133X
  
  [30X    [33X[0;6YNew functionality for dealing with representations of algebras, and in
        particular for semisimple Lie algebras.[133X
  
  [30X    [33X[0;6YNew  functionality  for binary relations on arbitrary sets, magmas and
        semigroups.[133X
  
  [30X    [33X[0;6YBidirectional  streams, allowing an external process to be started and
        then controlled [21Xinteractively[121X by [5XGAP[105X[133X
  
  [30X    [33X[0;6YA  prototype  implementation  of  algorithms  using  general  subgroup
        chains.[133X
  
  [30X    [33X[0;6YChanges in the behavior of vectors over small finite fields.[133X
  
  [30X    [33X[0;6YA  fifth  book  [21XNew  features for Developers[121X has been added to the [5XGAP[105X
        manual.[133X
  
  [30X    [33X[0;6YNumerous bug fixes and performance improvements[133X
  
  [33X[0;0YThe changes between the final release of [5XGAP[105X 3 (version 3.4.4) and [5XGAP[105X 4 are
  wide-ranging.  The  general  philosophy of the changes is two-fold. Firstly,
  many  assumptions  in  the  design  of  [5XGAP[105X  3 revealed its authors' primary
  interest  in  group theory, and indeed in finite group theory. Although much
  of  the  [5XGAP[105X 4 library is concerned with groups, the basic design now allows
  extension  to  other  algebraic structures, as witnessed by the inclusion of
  substantial  bodies  of  algorithms  for computation with semigroups and Lie
  algebras.  Secondly,  as  the  scale of the system, and the number of people
  using  and  contributing  to  it  has  grown, some aspects of the underlying
  system  have  proved to be restricting, and these have been improved as part
  of  comprehensive  re-engineering  of  the system. This has included the new
  method  selection  system, which underpins the library, and a new, much more
  flexible, [5XGAP[105X package interface.[133X
  
  [33X[0;0YDetails  of  these  changes  can be found in the document [21XMigrating to GAP 4[121X
  available          at          the          [5XGAP[105X         website,         see
  [7Xhttps://www.gap-system.org/Gap3/migratedoc.pdf[107X.[133X
  
  [33X[0;0YIt is perhaps worth mentioning a few points here.[133X
  
  [33X[0;0YFirstly,  much  remains  unchanged, from the perspective of the mathematical
  user:[133X
  
  [30X    [33X[0;6YThe  syntax  of that part of the [5XGAP[105X language that most users need for
        investigating mathematical problems.[133X
  
  [30X    [33X[0;6YThe great majority of function names.[133X
  
  [30X    [33X[0;6YData libraries and the access to them.[133X
  
  [33X[0;0YA number of visible aspects have changed:[133X
  
  [30X    [33X[0;6YSome  function names that need finer specifications now that there are
        more structures available in [5XGAP[105X.[133X
  
  [30X    [33X[0;6YThe  access  to  information  already  obtained  about  a mathematical
        structure.  In [5XGAP[105X 3 such information about a group could be looked up
        by  directly  inspecting  the group record, whereas in [5XGAP[105X 4 functions
        must be used to access such information.[133X
  
  [33X[0;0YBehind the scenes, much has changed:[133X
  
  [30X    [33X[0;6YA  new  kernel,  with  improvements  in  memory  management and in the
        language  interpreter,  as  well  as  new  features  such as saving of
        workspaces and the possibility of compilation of [5XGAP[105X code into C.[133X
  
  [30X    [33X[0;6YA  new  structure  to  the  library,  based upon a new type and method
        selection  system,  which  is  able  to  support  a  broader  range of
        algebraic computation and to make the structure of the library simpler
        and more modular.[133X
  
  [30X    [33X[0;6YNew and faster algorithms in many mathematical areas.[133X
  
  [30X    [33X[0;6YData  structures  and algorithms for new mathematical objects, such as
        algebras and semigroups.[133X
  
  [30X    [33X[0;6YA  new  and  more  flexible  structure  for  the  [5XGAP[105X installation and
        documentation,  which  means,  for example, that a [5XGAP[105X package and its
        documentation can be installed and be fully usable without any changes
        to the [5XGAP[105X system.[133X
  
  [33X[0;0YVery few features of [5XGAP[105X 3 are not yet available in [5XGAP[105X 4.[133X
  
  [30X    [33X[0;6YNot  all  of  the  [5XGAP[105X 3 packages have yet been converted for use with
        [5XGAP[105X 4.[133X
  
  [30X    [33X[0;6YThe  library  of crystallographic groups which was present in [5XGAP[105X 3 is
        now       part       of       a       [5XGAP[105X 4      package      [5XCrystCat[105X
        ([7Xhttps://www.gap-system.org/Packages/crystcat.html[107X)  by  V. Felsch and
        F. Gähler.[133X
  
