##############################################################################
##
#W  up2.gd                         XMOD Package                  Chris Wensley
#W                                                                 & Murat Alp
##
##  Declaration file for functions of the XMOD package.
##
#H  @(#)$Id: up2.gd,v 2.007 2006/07/05 gap Exp $
##
#Y  Copyright (C) 1999,2001 University of St. Andrews, North Haugh,
#Y                          St. Andrews, Fife KY16 9SS, Scotland
##
Revision.("xmod/gap/up2_gd") := 
    "@(#)$Id: up2.gd,v 2.007 2006/07/05 gap Exp $";

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##
#P  IsUp2dMapping( <map> )
#R  IsUp2dMappingObj( <map> )
#O  Up2dMappingObj( <obj>, <ims> )
##
##  A section|derivation is determined by a cat1-group|xmod + generator images
##
DeclareProperty( "IsUp2dMapping", IsGeneralMapping );
DeclareRepresentation( "IsUp2dMappingObj", 
    IsUp2dMapping and IsAttributeStoringRep,
    [ "Object2d", "GeneratorImages" ] );
DeclareOperation( "Up2dMappingObj", [ Is2dObject, IsHomogeneousList ] );

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##
#A  Object2d( <map> )
#A  GeneratorImages( <map> )
#A  ImagePositions( <map> )
##
DeclareAttribute( "Object2d", IsUp2dMapping );
DeclareAttribute( "GeneratorImages", IsUp2dMapping );
DeclareAttribute( "ImagePositions", IsUp2dMapping );

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##
#P  IsDerivation( <map> )
#P  IsSection( <map> )
##
DeclareProperty( "IsDerivation", IsUp2dMapping );
DeclareProperty( "IsSection", IsUp2dMapping );


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##                               Derivations                                ##
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#O  DerivationByImages                                     sets up the mapping
#O  DerivationByImagesNC                                   sets up the mapping
##
DeclareOperation( "DerivationByImages", [ Is2dObject, IsHomogeneousList ] );
DeclareOperation( "DerivationByImagesNC", [ Is2dObject, IsHomogeneousList ] );
##  usage: DerivationByImages( XM, im, [, true|false ] )

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#O  DerivationImage                  image of  r \in R  by the derivation  chi
##
DeclareOperation( "DerivationImage", [ IsDerivation, IsObject ] );

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#O  DerivationBySection  construct an XMod derivation from a cat1-group section
##
DeclareOperation( "DerivationBySection", [ IsSection ] );

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#O  PrincipalDerivation              derivation determined by choice of s in S
#A  PrincipalDerivations                         list of principal derivations
##
DeclareOperation( "PrincipalDerivation", [ IsXMod, IsObject ] );
DeclareAttribute( "PrincipalDerivations", IsXMod );

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#O  CompositeDerivation                 Whitehead composite of two derivations
##
DeclareOperation( "CompositeDerivation", [ IsDerivation, IsDerivation ] );

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##
#P  IsRegularDerivation                   so an element of the Whitehead group
##
DeclareProperty( "IsRegularDerivation", IsDerivation );

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##
#A  SourceEndomorphism       upmapping determines endomorphism of source group
#A  RangeEndomorphism        upmapping determines endomorphism of range group
#A  Object2dEndomorphism     upmapping determines endomorphism of xmod or cat1
##
DeclareAttribute( "SourceEndomorphism", IsUp2dMapping );
DeclareAttribute( "RangeEndomorphism", IsUp2dMapping );
DeclareAttribute( "Object2dEndomorphism", IsUp2dMapping );

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##
#O  InverseDerivations      Finds all semigroup inverses XJ for derivation Xi
##                                                i.e.  XiXjXi=Xi & XjXiXj=Xj
DeclareOperation( "InverseDerivations", [ IsDerivation ] );

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##
#O  ListInverseDerivations               List all inverses for each derivation
##
DeclareOperation( "ListInverseDerivations", [ IsXMod ] );


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##                                 Sections                                 ##
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#O  SectionByImages                                   sets up GroupHomByImages
#O  SectionByImagesNC                                 sets up GroupHomByImages
##
DeclareOperation( "SectionByImages", [ Is2dObject, IsGroupHomomorphism ] );
DeclareOperation( "SectionByImagesNC", [ Is2dObject, IsGroupHomomorphism ] );
##  usage: SectionByImages( C, im, [, true|false ] )

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#O  SectionByDerivation      the cat1-group section determined by a derivation
##
DeclareOperation( "SectionByDerivation", [ IsDerivation ] );

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#O  CompositeSection                       Whitehead composite of two sections
##
DeclareOperation( "CompositeSection", [ IsSection, IsSection ] );


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##                      Monoids of Derivations or Sections                 ##
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#P  IsMonoidOfUp2dMappings( <obj> )
#R  IsMonoidOfUp2dMappingsObj( <obj> )
##
##  An Up2dMappings record stores images lists and composition table
##
DeclareProperty( "IsMonoidOfUp2dMappings", IsObject );
DeclareRepresentation( "IsMonoidOfUp2dMappingsObj",
    IsMonoidOfUp2dMappings and IsAttributeStoringRep,
    [ "Object2d", "ImagesList" ] );

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##
#A  ImagesList                                returns list of DerivationImages
#A  AllOrRegular                                    type of derivations record
#A  ImagesTable                                   returns lists of image lists
##
DeclareAttribute( "ImagesList", IsMonoidOfUp2dMappings );
DeclareAttribute( "AllOrRegular", IsMonoidOfUp2dMappings );
DeclareAttribute( "ImagesTable", IsMonoidOfUp2dMappings );

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#O  MonoidOfUp2dMappingsObj( <obj>, <images>, <str> )
#P  IsMonoidOfDerivations                               
#P  IsMonoidOfSections
##
DeclareOperation( "MonoidOfUp2dMappingsObj",
    [ Is2dObject, IsHomogeneousList, IsString ] );
DeclareProperty( "IsMonoidOfDerivations", IsMonoidOfUp2dMappings );
DeclareProperty( "IsMonoidOfSections", IsMonoidOfUp2dMappings );

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##
#A  RegularDerivations    find all invertible derivations for a crossed module
#A  AllDerivations                   find all derivations for a crossed module
#A  RegularSections              find all invertible sections for a cat1-group
#A  AllSections                             find all sections for a cat1-group
##
DeclareAttribute( "RegularDerivations", IsXMod );
DeclareAttribute( "AllDerivations", IsXMod );
DeclareAttribute( "RegularSections", IsCat1 );
DeclareAttribute( "AllSections", IsCat1 );

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##
#O  BacktrackDerivationsJ          recursive function for BacktrackDerivations
#O  BacktrackDerivations            recursive construction for all derivations
#O  BacktrackSectionsJ         recursion used by RegularSections & AllSections
##
DeclareOperation( "BacktrackDerivationsJ",  [ IsXMod, IsHomogeneousList,
    IsHomogeneousList, IsHomogeneousList, IsInt, IsString ] );
DeclareOperation( "BacktrackDerivations", [ IsXMod, IsString ] );
DeclareOperation( "BacktrackSectionsJ", [ IsRecord, IsInt, IsObject, IsInt ] );

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##
#A  WhiteheadMonoidTable( XM )               Table of products of derivations
#A  WhiteheadGroupTable( XM )        Table of products of regular derivations
##
##  ?? should these refer just to 2dObjects ??
##
DeclareAttribute( "WhiteheadMonoidTable", IsXMod );
DeclareAttribute( "WhiteheadGroupTable", IsXMod );

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##
#A  WhiteheadPermGroup( XM )                     a permutation representation
#A  WhiteheadGroupGeneratingDerivations                   generators for W(X)
#A  WhiteheadGroupGeneratorPositions         positions of generators for W(X)
#A  WhiteheadTransMonoid( XM )                a transformation representation
##
DeclareAttribute( "WhiteheadPermGroup", IsXMod );
DeclareAttribute( "WhiteheadGroupGeneratingDerivations", IsXMod );
DeclareAttribute( "WhiteheadGroupGeneratorPositions", IsXMod );
DeclareAttribute( "WhiteheadTransMonoid", IsXMod );

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#E  up2.gd  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ends here
