CHANGES to the 'XMod' package

2.92 -> 2.92dev (03/01/2025)

(20/12/24) changed the examples of induced crossed modules in section 7.2
(17/12/24) implemented (Inner)ActorCat1Group, fixing issue #144
(20/11/24) added AutomorphismPermGroup method for cat1-groups renamed PermAutomorphismAsXModMorphism as PermAutomorphismAs2dGroupMorphism and added cat1-group method added WhiteheadRegularGroup and WhiteheadGroupIsomorphism removed the unused CompositeDerivation (= WhiteheadProduct) removed the unused (List)InverseDerivations renamed WhiteheadGroupGeneratingDerivations as ...UpMappings added WhiteheadGroupInverseIsomorphism fixed error in CrossedPairingByDerivations

2.91 -> 2.92 (23/01/2024)

(11/10/23) methods for WhiteheadXMod etc for xmods which are not perm
(16/02/23) now using the NC version of PreImagesRepresentative

2.89 -> 2.91 (16/02/2023)

(16/02/23) revised tst/extra/d24.tst so that it works with option -A
(09/02/23) added a chapter on double groupoids with operations EnhancedBasicDoubleGroupoid, DoubleGroupooidWithZeroBoundary
(05/02/23) added PreXModWithTrivialRange

2.88 -> 2.89 (04/02/2023)

(01/02/23) added RegularActionHomomorphism(Object/2DimensionalGroup)
(23/12/22) changed email address and other personal details
(24/08/22) manual: documented DerivationImage; corrected CrossDiagonalActions

2.86 -> 2.88 (28/04/2022)

(27/04/22) introduced Size2d for 2d-objects and Size3d for 3d-objects added the Arvasi/Odabas/Wensley paper to the list of references

2.85 -> 2.86 (14/03/2022)

(14/03/22) moved d24.tst to tst/failing temporarily

2.84 -> 2.85 (12/03/2022)

(12/03/22) commented out some tests that failed in gapdev
(24/11/21) NaturalHomomorphism -> NaturalHomomorphismByNormalSubgoup

2.83 -> 2.84 (15/11/2021)

(15/11/21) corrected address for CDW: https://github.com/cdwensley
(08/04/21) Switch CI to use GitHub Actions

2.82 -> 2.83 (17/02/2021)

(17/02/21) added functions for quasi-isomorphisms - manual section 3.5
(26/10/20) corrected ^ for morphisms of 2dimensional groups
(25/10/20) added examples/cpcpcp.g constructing 23 cat2-groups on (Cp)^3

2.81 -> 2.82 (23/10/2020)

(22/10/20) revised IsomorphismPreCat1Groups
(19/10/20) added IsSymmetric2DimensionalGroup
(25/08/20) removed perm groups as range in KernelCokernelXMod
(07/08/20) added the property IsSubEndoMapping to util.{gd,gi}
(20/07/20) revised the function AllXModsUpToIsomorphism etc.
(15/06/20) renamed/revised PreXModRecordOfPreCat1Group (and conversely)
(10/06/20) restructured cat1data.g so that the numbering agrees with HAP
(30/05/20) added HAP chapter to the manual plus XMod <-> HAP functions

2.79 -> 2.81 (25/05/2020)

(24/05/20) added AllCat2GroupsWithFixedUp(AndLeftRange)
(10/05/20) split gp3objmap.tst into gp3xs.tst and gp3cat2.tst added operation AllCat2GroupMatrix
(08/05/20) added DirectProductOp method for PreCat2Groups added PreCat2GroupMorphismByGroupHomomorphisms method

2.77 -> 2.79 (04/05/2020)

(04/05/20) added operation LoopClasses to go with (All)LoopsXMod
(03/05/20) reinstalling the package after hard disc replacement
(19/04/20) added operation DisplayLeadMaps for a HigherDimensionalDomain fixed an error in AllCat2GroupsWithImagesUpToIsomorphism
(16/04/20) fixed an error in the function GroupGroupoid
(03/04/20) added fields .symm1 and .siso1 to CatnGroupNumbers
(02/04/20) revised IsomorphismPreCat1Groups
(27/03/20) IsPreCat1GroupByEndomorphisms (ditto CatnGroup) -> IsPreCat1GroupWithIdentityEmbedding (IsomorphismTo)EndomorphismCat1Group -> IsomorphicPreCat1GroupWithIdentityEmbedding
(12/03/20) now SmallerDegreePermutationRepresentation2DimensionalGroup in place of SmallerDegreePerm2DimensionalDomain
(06/03/20) now running under GAP 4.11.0
(02/03/20) fixed issue 41, (Direct/Co)Product for more than two objects
(01/03/20) corrected DiagonalCat1Group
(29/02/20) added SubdiagonalCat1Group and IsSubXMod, IsSub***
(30/01/20) added tests on kernels in IsomorphismCat1Groups - valid??
(14/01/20) fixed IdentityMapping for cat2-groups and catn-groups
(10/01/20) revised CatnGroupNumbers fields for crossed squares & cat2-groups
(24/11/19) added DirectProduct for cat1-groups (& revised for xmods)

2.74 -> 2.77 (17/11/2019)

(17/11/19) fixed XModByGroupOfAutomorphisms and updated manual
(16/11/19) corrected Transpose3DimensionalGroup for cat2-groups
(12/11/19) reverted need for a cat2-group to have a diagonal cat1-group

2.73 -> 2.74 (11/10/2019)

(09/10/19) Cat1GroupOfXMod now a record storing embeddings of S,R in G
(01/10/19) added second example in section 8.2.14
(10/09/19) added methods for (Pre)CrossedSquareBy(Pre)XMods
(09/09/19) revised CrossedSquare consructors to use diag, not the action
(06/09/19) added allcat2pos to CatnGroupLists(G)
(03/09/19) major revision: PreCat2Group and DetermineRemainingCat1Groups
(02/09/19) replaced IsEndomorphismCat1Group by IsCat1GroupByEndomorphisms
(27/08/19) added AllCat3Groups, AllCat3GroupTriples, AllCat3GroupsNumber
(14/08/19) added AllCat1GroupMorphisms and simplified AllCat2GroupMorphisms
(13/08/19) changes to gp{2,3,4}map.gi to make cat2-xs.tst work for the paper
(07/08/19) functions for cat3-groups in gp4obj.g{d,i}
(30/07/19) modified induced.tst and isoclinic.tst to avoid gapdev diffs
(26/07/19) added .pairs and .fams to CatnGroupLists record
(17/07/19) modified .travis.yml in line with Max' changes in Utils
(17/07/19) added operation AllCat2GroupFamilies and updated the manual
(16/07/19) added attribute record CatnGroupNumbers for a group
(11/07/19) added new method for IsPreCat2GroupMorphism
(17/06/19) revised AllCat{1,2}... functions using iterators in utils-0.64
(10/06/19) complete rewrite of IsomorphismCat2Groups
(15/05/19) new AllCat{1,2}GroupsIterator, AllCat{1,2}GroupsNumber
(10/05/19) added in new functions from Alper for AllCat2Groups (up to iso)
(18/04/19) reorganised all .tst files into /tst/manual/ and /tst/extra/
(11/04/19) corrected UnionOfPiecesOp for prexmods with objects
(09/04/19) added names and examples of crossed pairing functions to manual
(13/03/19) added initial implementation of group groupoids (manual 2.8)

2.72 -> 2.73 (04/03/2019)

(04/03/19) Cat2GroupOfCrossedSquare now giving results again crossed pairings now consistently maps : N x M -> L
(16/02/19) added License field in PackageInfo.g
(08/12/18) added InducedXModByBijection, InducedXModByCoproduct and renamed SurjectiveInducedXMod, InclusionInducedXModByCopower
(06/12/18) added a CoproductXMod method for a list with more than two xmods
(05/12/18) added CrossedSquareByXModSplitting
(03/12/18) add CrossedSquareByAutomorphismGroup, CrossedPairingByConjugators
(01/12/18) added method for IsCrossedSquare
(28/11/18) new version of 2-argument functions in map2arg.{gd,gi}
(26/11/18) added CrossedSquareByPullback and XModByPullback
(21/11/18) added PrincipalCrossedPairing
(19/11/18) added IsNormalSub2DimensionalDomain and used this when calling CrossedSquareByNormalSubXMod
(15/11/18) renamed CrossedSquareMorphismByMorphisms as CrossedSquareMorphismByXModMorphisms and added CrossedSquareMorphismByGroupHomomorphisms; ditto for Cat2GroupMorphisms XModMorphismByHoms -> XModMorphismByGroupHomomorphisms
(14/11/18) Cat1Morphism -> Cat1GroupMorphism, ditto Cat2Morphism, etc. removed IsomorphismSmallPermGroup, NiceObject, etc from util.*
(08/11/18) added KernelCokernelXMod, fixing issue #34
(07/11/18) XModByAutomorphismGroup is now an attribute, not a global fn.
(07/11/18) fixed problem with Cat2GroupOfCrossedSquare
(06/11/18) added special case of InducedXMod when iota is bijective

2.69 -> 2.72 (16/09/2018)

(10/09/18) replaced PrintOneItemPerLine(L); with Perform(L,Display);
(02/09/18) added CrossedPairingByXModAction, CrossedSquareByNormalSubXMod
(30/08/18) PreCat2GroupOfPreCrossedSquare revised : q8xscat2.tst, d24.tst
(07/08/18) added PreCat2GroupByPreCat1Groups and other changes to gp3obj.*
(01/08/18) fixed issue #24 and added xtst/cat1data.tst
(30/07/18) fixed issue #9

2.68 -> 2.69 (20/07/2018)

(12/07/18) added operations InducedXModFromTrivialSource/Range
(05/07/18) major revision of InclusionInducedXModByCopower
(29/06/18) added method for IsCentralExtension2DimensionalGroup
(28/06/18) added operation DisplacementGroup; changed DisplacementSubgroup
(17/05/18) corrected SinglePiecePreXModWithObjects in the discrete case

2.67 -> 2.68 (01/05/2018)

(30/04/18) made tests more robust; moved coprod.tst to /xtst

2.66 -> 2.67 (29/04/2018)

(23/04/18) avoid use of FactorGroup - just use Image( nat )
(19/04/18) replace Image(f,x) by ImageElm(f,x) throughout

2.65 -> 2.66 (12/04/2018)

(12/04/18) added LoopsXMod functions: apps.{gd,gi,xml}, loops.{g,tst}

2.64 -> 2.65 (21/03/2018)

(18/03/18) remove some of the temporary synonyms (09/08/17)
(13/02/18) CompositeDerivation/Section now WhiteheadProduct SectionByImages now SectionByHomomorphism added IdentityDerivation; IdentitySection; WhiteheadOrder
(12/02/18) AllOrRegular now DerivationClass; revised PrincipalDerivations
(10/01/12) converted LaTeX entities back in to newcommands
(09/01/18) now using AutoDoc to build the manual
(15/12/17) removed examples/; added expt/; *.tst files in xtst/

2.63 -> 2.64 (30/11/2017)

(29/11/17) fixed tests to work with both 4r8 and dev in 3 options
(23/11/17) removed attribute AutoGroup (=Range(XModAction)) for xmods
(22/11/17) added operations SinglePiecePreXModWithObjects(NC)
(16/11/17) added Root2dGroup for prexmods with objects
(17/10/17) ImageElmXModAction now working for xmods of groupoids
(04/10/17) added operation ImageElmXModAction
(01/10/17) renamed test files and made them independent
(27/09/17) added tst/testextra.g, tst/allxmods.xtst, tst/cat1mor.xtst

2.61 -> 2.63 (26/09/2017)

(26/09/17) added a number of Types and modified Objectify statements removed Up2DimensionalMappingObj
(24/08/17) changed the name of Murat's university
(09/08/17) in order to keep XModAlg-1.12 working, added synonyms Is2dDomain for Is2DimensionalDomain, PreCat1ByTailHeadEmbedding for PreCat1Obj, PreCat1ByEndomorphisms for PreCat1GroupByEndomorphisms PreCat1ByPreXMod for PreCat1GroupOfPreXMod IsGeneral2dMapping for IsGeneral2DimensionalMapping and Kernel2dMapping for Kernel2DimensionalMapping

2.59 -> 2.61 (07/08/2017)

(07/08/17) Gpd changed to groupoids in list of required packages
(07/08/17) testall.g now calls TestDirectory; test files renamed
(07/08/17) temporarily renamed 08-gpd2obj.tst and 11-gpnobjmap.tst so that they do not get tested by TestDirectory("tst")
(21/07/17) replaced PreXModIsomorphismByIsomorphisms by the more general IsomorphismByIsomorphisms; then functions such as IsomorphismPerm2DimensionalGroup rewritten to use it.
(20/07/17) added IsomorphismByIsomorphisms for pre1-cat-groups
(20/07/17) Removed duplication in 'Of' and 'By' operations
(17/07/17) new functions added by Alper for crossed square <-> cat2-group: ConjugationActionForCrossedSquare; ElementsRelationsForSemidirectProduct
(14/06/17) added methods for String, ViewString, PrintString
(09/05/17) dom2d3d.g{d,i} renamed dom2dnd.g{d,i} hdim-morphisms now expect [ src, rng, list of maps ] PreCatn(Mapping)Dimension now HigherDimension added attribute VertexGroups for HigherDimensionalGroups
(08/05/17) Removed lots of 3Dim stuff since HigherDim stuff is better
(05/05/17) AllCat1Groups* -> AllCat1DataGroups*
(04/05/17) Alper add catn-morphism functions in gpnmor.g{d,i}
(29/04/17) added lines to makedoc.g to allow for xymatrix commands
(24/04/17) 2d becomes 2Dimensional (except Object2d)
(22/04/17) Alper added lib/gpnobj.gd, lib/gpnobj.gi, tst/gpnobjmap.tst
(10/04/17) Alper added a number of functions for cat2-groups and morphisms Replaced XPairing with CrossedPairing
(04/04/17) added CoproductInfo for coproducts FactorXMod now FactorPreXMod (ditto NaturalMorphisms)
(27/03/17) added Is2dGroupMorphismData and modified construction functions Method for IsNormal now applies to precrossed modules added PeifferSub2dGroup
(24/03/17) added operation DiagonalCat1 and example S3xS3 => S3
(22/03/17) added operation CoproductXMod and files coprod.g, coprod.tst

2.58 -> 2.59 (21/03/2017)

(21/03/17) added property IsEndomorphismPreCat1 modified IsomorphismPerm2dGroup for PreCat1 objects
(14/11/16) "first author" -> "second author" in manual.xml (issue #4)

2.56 -> 2.58 (02/11/2016)

(18/10/16) now using bibliography file bib.xml of type bibxmlext.dtd
(13/10/16) changed package releases to https://gap-packages.github.io/xmod
(24/03/16) added files hap.gd, hap.gi
(16/03/16) edited utils.tst to remove functions transferred to Utils

2.51 -> 2.56 (08/03/2016)

(23/02/16) remove functions from util.g{d/i} now in Utils; require Utils
(18/02/16) removed date/version info from file headers
(16/02/16) require Gpd >= 1.42;

2.45 -> 2.51 (09/02/2016)

(08/02/16) necessary changes to test files to fix new output errors

2.44 -> 2.45 (29/12/2015)

(29/12/15) fixed changes in output from \*.tst files

2.42 -> 2.44 (13/11/2015)

(11/11/15) renamed Rank and MiddleLength and now for p-groups only
(10/11/15) changes examples in tests to avoid repeated variable names
(09/11/15) XPair -> XPairing, etc.
(08/11/15) IsomorphismPermPre(XMod/Cat1) -> IsomorphismPerm2dGroup, etc.
(07/11/15) Revised manual, chapter 7, and isoclinic.tst
(06/11/15) IsStemGroup & IsStemXMod -> IsStemDomain etc.
(04/11/15) RestrictionMappingGroups -> GeneralRestgrictedMapping
(01/11/15) makedocrel.g : added MathJax; changed "doc" to XModDoc
(20/10/15) moved code from FactorXMod to NaturalMorphismByNormalSubXMod corrected formulae in Displacement and DisplacementSubgroup
(19/10/15) revised Isoclinism for xmods; IsoAllXMods -> AllXModsUpToIso..
(16/10/15) changed all occurrences of XSq to CrossedSquare
(15/10/15) fixed Iterator bug in Isoclinism for groups
(13/10/15) CentralQuotient now a crossed module or a crossed square added LeftRightMorphism and UpDownMorphism for crossed squares
(07/10/15) AllXMods and AllPreXMods now global functions added property IsStemXMod
(06/10/15) renamed IsIsomorphicXMod as IsomorphismXMods; fixed the call to IsXMod in PreXModObj
(05/10/15) added Centralizer and Normalizer methods for crossed modules
(02/10/15) added ExternalSetXMod
(01/10/15) added operation Displacement
(28/09/15) added AllStemGroupFamilies and Set various Names
(26/09/15) added NaturalHomomorphismByNormalSubXMod
(24/09/15) added CrossActionSubgroup
(23/09/15) removed last occurrences of AllIsomorphisms
(22/09/15) added functions for isoclinism of groups
(18/09/15) processed a number of properties in the isoclinic files
(17/09/15) added example in manual subsection 2.1.4.
(15/09/15) methods for InnerMorphism, ActorXMod, CentreXMod, etc. now specified only for permutation crossed modules
(24/08/15) major edits to README, including GitHub issues link

2.41 -> 2.42 (24/08/2015)

(24/08/15) made version to be moved from Bitbucket to GitHub
(20/07/15) fixed bug in IsomorphismPcPreCat1 reported by Charles Melville

2.32 -> 2.41 (05/06/2015)

(05/06/15) gpd2obj.gd changed to reflect changes in package Gpd

2.31 -> 2.32 (26/02/2015)

(26/02/15) reverted AllInducedXMods(Cat1s) to global functions
(03/02/15) added properties IsPreXModDomain and IsPreCat1Domain which are meant to apply to both group and algebra cases
(02/02/15) took out all MultiplicativeElementWithTuple's etc. and Multiplicative2dElement's etc.
(29/01/15) made copies of dom2d3d,g{d,i} and gp2obj.g{d,i} before embarking on a major rewrite of the category structure: specifically, changing lots of '2dDomain's into '2dGroup's

2.26 -> 2.31 (17/12/2014)

(17/12/14) moved package home page to <pages.bangor.ac.uk/~mas023/chda/xmod/>
(08/11/14) created BitBucket repository for 'XMod'

2.22 -> 2.26 (26/11/2013)

(26/11/13) minor mod to WhiteheadTransMonoid to fix gp2up.tst output
(03/11/13) fixed errors in cat1data.g reported by Van Luyen Le.
(15/10/13) fixed error in Cat1MorphismByXModMorphism.
(03/10/13) completed work on groups of order [64..70] in cat1data.g
(02/10/13) added operation CollectPartsAlreadyDone.
(01/10/13) added operation PreCat1IsomorphismByIsomorphisms.
(17/08/13) fixed bug in PermCat1Select sent by Van Luyen Le
(26/03/13) put groups of order 64 back into cat1data.g
(05/02/13) rewrite of testall.g following Alex K's wedderga example

2.19 -> 2.22 (25/01/2013)

(25/01/13) Minor change to test file output to avoid problems in tests.
(09/01/13) Changed PackageWWWHome, using "gap4" rather than "gap4r5". Unable to fix problems related to changes in lib/ghom.gi, so removed gpd2obj.tst from the set of standard tests: the problem is with changes to GroupGeneralMappingByImages.
(26/09/12) Moved functions to the new cat1data.gd, cat1data.gi.
(21/09/12) Edited test files to reflect recent changes
(12/07/12) Changed the format and rebuilt the data file cat1data.g :- it is now assumed that the SmallGroups library is used. Extended cat1data.g from order 47 to most of order 64. Major revision of AllCat1s, MakeAllCat1s, Cat1Select
(04/07/12) Added AllCat1s and IsomorphismPreCat1s (from GAP3 version). Removed batch of functions from util.g{d,i} involving EndomorphismClasses, IdempotentImages, etc. Replaced their use in AllCat1s with calls to GQuotients.

2.18 -> 2.19 (09/06/2012)

(08/06/12) Following the replacement of IdentitySubgroup by TrivialSubgroup in Gpd, renamed IdentitySubXMod by TrivialSubXMod, etc. All calls of GroupHomomorphismByImagesTriv returned to GroupHomomorphismByImages (see item dated 30/04/08)
(07/06/12) Renamed special Display for lists as PrintListOneItemPerLine following email from Max Horn

2.17 -> 2.18 (23/04/2012)

(23/04/12) added autpgrp as a needed package
(26/01/12) replaced XModActedUpon by AutomorphismDomain in gp2act.g{d,i}
(25/01/12) fixed error in XModByGroupOfAutomorphisms (oneG now oneP)
(10/01/12) updated to 2012; corrected URLs in intro.xml
(15/12/11) now requires version 1.13 of 'Gpd'

2.15 -> 2.17 (21/09/2011)

(20/09/11) new version of makedocrel.g for building the manual added file gpd/examples/readall.g for testing purposes
(17/09/11) Shortened the banner.
(16/09/11) Renamed subdirectory xmod/gap as xmod/lib

2.14 -> 2.15 (06/09/2011)

(04/09/11) Changed BIND_GLOBAL to BindGlobal, since it is safer
(16/08/11) changed directory for archive to .../chda/gap4r5/xmod/

2.13 -> 2.14 (30/07/2011)

(30/07/11) final adjustments to the test files
(29/07/11) major changes to gp3objmap.g{d,i}.
(28/07/11) new 16/07/11 files now dom2d3d.gd etc.
(27/07/11) ViewObj, PrintObj, Display, Name now methods for 2d-groups.
(19/07/11) IsUp2dMapping now a category. InducedXMod( s4, s3b, s3b ) fails due to iso to pc-group, fo forced (for now) an isomorphism to a perm group.
(18/07/11) Centre of an xmod no longer works, so brought back XModCentre.
(16/07/11) Introduced a range of new categories in files dom2d.gd, dom2d.gi, map2d.gd, map2d.gi. As a result there were many changes in all files.
(08/07/11) Changed headers of all files.
(06/07/10) Changed XModByGroupOfAutomorphisms(G) in case G is pcgroup
(02/07/10) New email address for Murat
(30/06/10) Added check for IsPc2dDomain to PreXModObj
(30/06/10) InducedXModByCopower now constructs a PcXMod if appropriate
(28/06/10) Added methods for IsomorphismPcPreXMod, IsomorphismPcPreCat1
(12/03/10) Moved 'XMod' development to IMac at home, and started v.2.14

2.12 -> 2.13 (21/01/2010)

(21/01/10) Changed output of AllInducedXMods to list of StructureDesc.

2.11 -> 2.12 (24/11/2008)

(19/11/08) GapDoc relegated to "suggested other packages".

2.008 -> 2.11 (13/11/2008)

(13/11/08) added GNU General Public License declaration, moved some 'XMod' utilities to gpd/gap/util.g{d,i},
(07/11/08) Changed website to: <www.maths.bangor.ac.uk/chda/xmod/> Split the test file into one file per chapter.
(30/04/08) Added GroupHomomorphismByImagesTriv to util.gd, util.gi to allow both and to be empty: triv -> triv! Fixed bug in XModOfCat1 in assigning names. FixedBug in Boundary for a pre-cat1-group.
(31/03/08) Added function GpdBuildManualHTML()
(16/03/08) renamed Tail,Head as TailMap,HeadMap (for benefit of 'Gpd')
(08/10/07) started this CHANGES file; changed directory permissions from 711 to 755; renamed files: obj2 -> gp2obj, etc, ready for groupoids; added file testall.g in xmod/tst

2.007 -> 2.008 (25/10/2006)

Fixed broken links in PackageInfo.g.

2.006 -> 2.007 (20/10/2006)

Added basic functions for crossed squares, considered as 3dObjects
with crossed pairings, and their morphisms. (Groups with two normal subgroups, and the actor of a crossed module, provide standard examples. Cat2-groups are not yet implemented.)
Converted the documentation to the format of the GAPDoc package, and added the function XModBuildManual() to the util.gi file.
Improved AutomorphismPermGroup for crossed modules, and introduced a special method for conjugation crossed modules.
Substantial revisons made to XModByCentralExtension, NorrieXMod, LueXMod, ActorXMod, and InclusionInducedXModByCopower.
Reintroduced the Cat1Select operation.

2.005 -> 2.006 (04/09/2004)

Changed morphism functions to return fail when invalid data is supplied, rather than calling Error.
Fixed a bug in XModByGroupOfAutomorphisms.

2.004 -> 2.005 (16/04/2004)

Moved the example files from tst/test_i.g to examples/example_i.g,
converted testmanual.g to a proper test file tst/xmod_manual.tst.
Replaced OperationHomomorphism by ActionHomomorphism, a general GAP;4.4 change.
Finished replacing RModule by AbelianModule.
Renamed UpMapping as Up2dMapping.
Added MappingGeneratorsImages and InverseGeneralMapping
for a 2dMapping.
A significant change was the conversion of the actor crossed module functions from the 3.4.4 version, including AutomorphismPermGroup for a crossed module, WhiteheadXMod, NorrieXMod, LueXMod, ActorXMod, Centre of a crossed module, InnerMorphism and InnerActorXMod.
Added SmallerDegreePermPreXMod after discovering, in the library, the very useful SmallerDegreePermutationRepresentation.

2.002 -> 2.004 (14/04/2004)

gave a new email address for Murat Alp
added the Cat1Select functionality of version 1 to the Cat1 function

2.001 -> 2.002 (January 2004)

Version 2.002 was prepared for the 4.4 release at the end of January 2004, and so required a PackageInfo.g file.

Induced Crossed Modules (May 2002)

Converted combinatorial functions -- DistinctRepresentatives, CommonRepresentatives, CommonTransversal and IsCommonTransversal.

Converted Tietze modification functions TzCommutatorPair, TzPartition and FactorsPresentation.

Introduced global functions IsomorphismPermObject, IsomorphismFpObject, and IsomorphismPcObject which call IsomorphismPermGroup etc. when the object is a group. Added functions IsomorphismPermPreXMod, IsomorphismPermPreCat1, etc. to be called when the object is a 2d-object.

Added IsomorphismXModByNormalSubgroup which applies when the boundary of the xmod is injective.

Added PreXModIsomorphismByIsomorphisms (but renamed 21/07/17) (we also need a similar function PreCat1IsomorphismByIsomorphisms) where the data consists of a crossed module, an isomorphism of the source, and an isomorphism of the range.

Changed RModule to AbelianModule.

Version 2.001 for GAP 4 (April 2002)

Generic name UpMapping chosen for derivations and sections (later changed to Up2dMapping).

File names changed to obj2.gd, map2.gi, up2.tex, etc.

Added alternative methods for IsomorphismPermGroup for 2dObjects.

Sorted a problem with fixing the generating set for R when used to define derivations. The (old) code used an fp-group version of R and checks that all the relators map by chi to 1. Unfortunately, IsomorphismFpGroup sometimes permutes the order of the R-generators, with unfortunate effects.
The fix used IsomorphismFpGroupByGenerators, which returns the images of the generators specified in the function call.
We have also used genR := StrongGeneratorsStabChain( StabChain( rng ) ); throughout to specify the generators of R.

Operation XModMorphism renamed as XModMorphismByHoms, and a new global function XModMorphism introduced (ditto for other 2dMappings).

Now using \chi_1 \star \chi_2 for Whitehead multiplication (on the right), with CompositeDerivation still giving multiplication on the left.
This means that the second axiom for derivations and for sections has changed -- see Chapter 4.

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