  
  [1X1 The GAP Table of Marks Library[0X
  
  
  [1X1.1 Tables Of Marks[0X
  
  The  concept  of  a  [13XTable of Marks[0m was introduced by W.Burnside in his book
  ``Theory  of Groups of Finite Order'' [Bur55]. Therefore a table of marks is
  sometimes  called  a [13XBurnside matrix[0m. The table of marks of a finite group G
  is  a matrix whose rows and columns are labelled by the conjugacy classes of
  subgroups  of  G and where for two subgroups H and K the (H, K)–entry is the
  number of fixed points of K in the transitive action of G on the cosets of H
  in  G.  So  the  table  of  marks  characterizes  the set of all permutation
  representations  of  G.  Moreover,  the  table  of  marks  gives  a  compact
  description  of  the  subgroup lattice of G, since from the numbers of fixed
  points  the  numbers of conjugates of a subgroup K contained in a subgroup H
  can  be derived. For small groups the table of marks of G can be constructed
  directly  in  GAP  by  first  computing  the  entire  subgroup lattice of G.
  However, for larger groups this method is unfeasible. The GAP Table of Marks
  library  provides access to several hundred table of marks and their maximal
  subgroups.
  
  
  [1X1.2 Installing The Table of Marks Library[0X
  
  Download  the  archives in your preferred format. Unpack the archives inside
  the pkg dirctory of your GAP installation. Load the package
  
  [4X---------------------------  Example  ----------------------------[0X
    [4Xgap> LoadPackage("tomlib");[0X
    [4Xtrue[0X
  [4X------------------------------------------------------------------[0X
  
  
  [1X1.3 Contents[0X
  
  TomLib  contains several hundred tables of marks. For a complete list of the
  contents of the library do the following.
  
  [4X---------------------------  Example  ----------------------------[0X
    [4Xgap> names:=AllLibTomNames();;[0X
    [4Xgap> "A5" in names;[0X
    [4Xtrue[0X
  [4X------------------------------------------------------------------[0X
  
  The current version of the tomlib contains the tables of marks of the groups
  listed  below  as  well as the tables of many of their maximal subgroups and
  automorphism groups. The Alternating groups A_n
  
  --    for n = 5, 6, 7, 8, 9, 10, 11, 12, 13.
  
  The Symmetric groups S_n
  
  --    for n = 4, 5, 6, 7, 8, 9, 10, 11, 12, 13.
  
  The Linear groups L_2(n) for
  
  --    n  = 7, 8, 11, 13, 16, 17, 19, 23, 25, 27, 29, 31, 32, 37, 41, 43, 47,
        49, 53
  
  --    n  =  59,  61, 64, 67, 71, 73, 79, 81, 83, 89, 97, 101, 103, 107, 109,
        113, 121, 125 .
  
  along with
  
  --    L_3(4), L_3(3), L_3(5), L_3(7), L_3(9)
  
  --    L_4(3), L_3(8), L_3(11).
  
  The Unitary groups
  
  --    U_3(3), U_4(3), U_3(5), U_3(4), U_3(11), U_3(7), U_3(8)
  
  --    U_3(9), U_4(2), U_5(2)
  
  The Sporadic Groups
  
  --    HS, McL, He, J_1, J_2, J_3, M_11, M_12, M_22, M_23, M_24
  
  The  names  given  to each subgroup are consistent with those used in Robert
  Wilon's  atlas  [ATLAS] For example if you wish to access the table of marks
  of  the  maximal  subgroup  "5:4  x  A5"  of  the  Higman-Sims  group do the
  following:
  
  [4X---------------------------  Example  ----------------------------[0X
    [4Xgap> TableOfMarks("5:4 x A5");[0X
    [4XTableOfMarks( "5:4 x A5" )[0X
  [4X------------------------------------------------------------------[0X
  
  
  [1X1.4 Administrative Functions[0X
  
  Here  we  document  some  of  the  administrative facilities for the the [5XGAP[0m
  library of tables of marks.
  
  [1X1.4-1 LIBTOMKNOWN[0m
  
  [2X> LIBTOMKNOWN________________________________________________[0Xglobal variable
  
  [10XLIBTOMKNOWN[0m  is  a record that controls the loading of data files of the [5XGAP[0m
  library of tables of marks. It has the following components.
  
  [8X[10XACTUAL[0m[8X [0m
        the   name   of   the   file   to  be  read  at  the  moment  (set  by
        [10XSetActualLibFileName[0m),
  
  [8X[10XLOADSTATUS[0m[8X [0m
        a  record whose components are names of files in the library of tables
        of  marks,  with  value  a  list whose first entry is one of [10X"loaded"[0m,
        [10X"unloaded"[0m,  [10X"userloaded"[0m  and  whose  second entry is an integer that
        controls  when  the  corresponding tables of marks can be removed from
        [5XGAP[0m,
  
  [8X[10XMAX[0m[8X [0m
        [5XGAP[0m  remembers at most [10XMAX[0m of the previously loaded library files (the
        default value is 10),
  
  [8X[10XUNLOAD[0m[8X [0m
        is  it  allowed  to  remove previously loaded library files (is set to
        [9Xtrue[0m by default),
  
  [8X[10XSTDGEN[0m[8X [0m
        a  list  describing standard generators of almost simple groups in the
        table of marks library.
  
  Additionally  the  names  of the files already loaded occur as components of
  [10XLIBTOMKNOWN[0m; the corresponding values are given by the data of the files.
  
  [1X1.4-2 IsLibTomRep[0m
  
  [2X> IsLibTomRep( [0X[3Xobj[0X[2X ) _________________________________________[0XRepresentation
  
  Library  tables of marks have their own representation. [10XIsLibTomRep[0m tests if
  [3Xobj[0m is a library representation.
  
  [1X1.4-3 TableOfMarksFromLibrary[0m
  
  [2X> TableOfMarksFromLibrary( [0X[3Xstring[0X[2X ) ________________________________[0Xfunction
  [6XReturns:[0X  the table of marks with name [3Xstring[0m.
  
  [1X1.4-4 ConvertToLibTom[0m
  
  [2X> ConvertToLibTom( [0X[3Xrecord[0X[2X ) ________________________________________[0Xfunction
  
  [10XConvertToLibTom[0m     converts     a     record     with    components    from
  [10XTableOfMarksComponents[0m  into  a  library  table  of  marks  object  with the
  corresponding attribute values set.
  
  [1X1.4-5 SetActualLibFileName[0m
  
  [2X> SetActualLibFileName( [0X[3Xfilename[0X[2X ) _________________________________[0Xfunction
  
  Sets the file name for [3Xfilename[0m.
  
  [1X1.4-6 LIBTOM[0m
  
  [2X> LIBTOM( [0X[3Xarg[0X[2X ) ____________________________________________________[0Xfunction
  [2X> AFLT( [0X[3Xsource, destination, fusion[0X[2X ) ______________________________[0Xfunction
  [2X> ACLT( [0X[3Xidentifier, component, value[0X[2X ) _____________________________[0Xfunction
  
  The  library  format  of  a library table of marks is a call to the function
  [10XLIBTOM[0m, with the arguments sorted as in [10XTableOfMarksComponents[0m .
  
  [10XAFLT[0m adds a fusion map [3Xvalue[0m from the table of marks with name [3Xsource[0m to the
  table  of  marks with name [3Xdestination[0m. The fusion map is a list of positive
  integers,  storing  at  position  i the position of the class in [3Xdestination[0m
  that contains the subgroups in the i-th class of [3Xsource[0m.
  
  [10XACLT[0m adds the value [3Xvalue[0m of a component with name [3Xcomponent[0m to the table of
  marks with identifier value [3Xidentifier[0m in the library of tables of marks.
  
  [1X1.4-7 AllLibTomNames[0m
  
  [2X> AllLibTomNames( [0X[3X[0X[2X ) _______________________________________________[0Xfunction
  [6XReturns:[0X  a list containing all names of available library tables of marks.
  
  [1X1.4-8 NamesLibTom[0m
  
  [2X> NamesLibTom( [0X[3Xstring[0X[2X ) ___________________________________________[0Xattribute
  [2X> NamesLibTom( [0X[3Xtom[0X[2X ) ______________________________________________[0Xattribute
  [6XReturns:[0X  all  names  of  the library table [3Xtom[0m or of the library table with
            name [3Xstring[0m
  
  [1X1.4-9 NotifiedFusionsOfLibTom[0m
  
  [2X> NotifiedFusionsOfLibTom( [0X[3Xtom[0X[2X ) __________________________________[0Xattribute
  [2X> NotifiedFusionsOfLibTom( [0X[3Xstring[0X[2X ) _______________________________[0Xattribute
  [2X> FusionsOfLibTom( [0X[3Xtom[0X[2X ) __________________________________________[0Xattribute
  [2X> FusionsOfLibTom( [0X[3Xstring[0X[2X ) _______________________________________[0Xattribute
  
  Are  there  any  fusions from the library table of marks [3Xtom[0m or the table of
  marks with name [3Xstring[0m into other library tables marks?
  
  [10XNotifiedFusionsOfLibTom[0m  returns  the  names  of  all  such tables of marks.
  [10XFusionsOfLibTom[0m returns the complete fusion maps. For that the corresponding
  library file has to be loaded.
  
  [1X1.4-10 NotifiedFusionsToLibTom[0m
  
  [2X> NotifiedFusionsToLibTom( [0X[3Xtom[0X[2X ) __________________________________[0Xattribute
  [2X> NotifiedFusionsToLibTom( [0X[3Xstring[0X[2X ) _______________________________[0Xattribute
  [2X> FusionsToLibTom( [0X[3Xtom[0X[2X ) __________________________________________[0Xattribute
  [2X> FusionsToLibTom( [0X[3Xstring[0X[2X ) _______________________________________[0Xattribute
  
  Are  there any fusions from other library table of marks to [3Xtom[0m or the table
  of marks with name [3Xstring[0m.
  
  [10XNotifiedFusionsToLibTom[0m  returns  the  names  of  all  such tables of marks.
  [10XFusionsToLibTom[0m returns the complete fusion maps. For that, the correponding
  library files have to be loaded.
  
  [1X1.4-11 UnloadTableOfMarksData[0m
  
  [2X> UnloadTableOfMarksData( [0X[3X[0X[2X ) _______________________________________[0Xfunction
  
  [10XUnloadTableOfMarksData[0m clears the cache of tables of marks. This can be used
  to free up to several hundred megabytes of space in the current [5XGAP[0m session.
  
  
  [1X1.5 Standard Generators of Groups[0X
  
  An  s-tuple of [13Xstandard generators[0m of a given group G is a vector (g_1, g_2,
  ...,  g_s)  of elements g_i in G satisfying certain conditions (depending on
  the isomorphism type of G) such that
  
  (1)   < g_1, g_2, ..., g_s > = G and
  
  (2)   the  vector  is unique up to automorphisms of G, i.e., for two vectors
        (g_1,  g_2, ..., g_s) and (h_1, h_2, ..., h_s) of standard generators,
        the map g_i -> h_i extends to an automorphism of G.
  
  For details about standard generators, see [Wil96].
  
  [1X1.5-1 StandardGeneratorsInfo[0m
  
  [2X> StandardGeneratorsInfo( [0X[3XG[0X[2X ) _____________________________________[0Xattribute
  
  When  called  with  the  group  [3XG[0m,  [2XStandardGeneratorsInfo[0m returns a list of
  records  with  at  least  one of the components [10Xscript[0m and [10Xdescription[0m. Each
  such  record defines [13Xstandard generators[0m of groups isomorphic to [3XG[0m, the i-th
  record  is  referred  to  as  the  i-th  set of standard generators for such
  groups.  The  value  of  [10Xscript[0m  is  a  dense list of lists, each encoding a
  command that has one of the following forms.
  
  [8XA [13Xdefinition[0m[8X [ i, n, k ] or [ i, n ][0m
        means  to search for an element of order n, and to take its k-th power
        as candidate for the i-th standard generator (the default for k is 1),
  
  [8Xa [13Xrelation[0m[8X [ i_1, k_1, i_2, k_2, ..., i_m, k_m, n ] with m > 1[0m
        means  a  check  whether the element g_{i_1}^{k_1} g_{i_2}^{k_2} cdots
        g_{i_m}^{k_m}  has  order  n;  if  g_j  occurs then of course the j-th
        generator must have been defined before,
  
  [8Xa [13Xrelation[0m[8X [ [ i_1, i_2, ..., i_m ], [3Xslp[0m[8X, n ][0m
        means  a  check  whether  the  result of the straight line program [3Xslp[0m
        (see [14X'Reference:  Straight  Line  Programs'[0m) applied to the candidates
        g_{i_1},  g_{i_2},  ..., g_{i_m} has order n, where the candidates g_j
        for the j-th standard generators must have been defined before,
  
  [8Xa [13Xcondition[0m[8X [ [ i_1, k_1, i_2, k_2, ..., i_m, k_m ], f, v ][0m
        means   a   check   whether  the  [5XGAP[0m  function  in  the  global  list
        [2XStandardGeneratorsFunctions[0m  ([14X1.5-3[0m) that is followed by the list f of
        strings returns the value v when it is called with G and g_{i_1}^{k_1}
        g_{i_2}^{k_2} cdots g_{i_m}^{k_m}.
  
  Optional components of the returned records are
  
  [8X[10Xgenerators[0m[8X[0m
        a string of names of the standard generators,
  
  [8X[10Xdescription[0m[8X[0m
        a  string describing the [10Xscript[0m information in human readable form, in
        terms of the [10Xgenerators[0m value,
  
  [8X[10Xclassnames[0m[8X[0m
        a  list  of  strings,  the  i-th entry being the name of the conjugacy
        class  containing  the i-th standard generator, according to the [5XAtlas[0m
        character table of the group (see [2XClassNames[0m ([14XReference: ClassNames[0m)),
        and
  
  [8X[10XATLAS[0m[8X[0m
        a boolean; [9Xtrue[0m means that the standard generators coincide with those
        defined  in Rob Wilson's [5XAtlas[0m of Group Representations (see [ATLAS]),
        and [9Xfalse[0m means that this property is not guaranteed.
  
  There  is  no  default  method  for  an arbitrary isomorphism type, since in
  general the definition of standard generators is not obvious.
  
  The          function          [2XStandardGeneratorsOfGroup[0m         ([14XReference:
  StandardGeneratorsOfGroup[0m)  can  be  used  to  find standard generators of a
  given group isomorphic to [3XG[0m.
  
  The  [10Xgenerators[0m  and  [10Xdescription[0m  values,  if not known, can be computed by
  [2XHumanReadableDefinition[0m ([14X1.5-2[0m).
  
  [4X---------------------------  Example  ----------------------------[0X
    [4Xgap> StandardGeneratorsInfo( TableOfMarks( "L3(3)" ) );[0X
    [4X[ rec( ATLAS := true, [0X
    [4X      description := "|a|=2, |b|=3, |C(b)|=9, |ab|=13, |ababb|=4", [0X
    [4X      generators := "a, b", [0X
    [4X      script := [ [ 1, 2 ], [ 2, 3 ], [ [ 2, 1 ], [ "|C(",, ")|" ], 9 ], [0X
    [4X          [ 1, 1, 2, 1, 13 ], [ 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 4 ] ] ) ][0X
  [4X------------------------------------------------------------------[0X
  
  [1X1.5-2 HumanReadableDefinition[0m
  
  [2X> HumanReadableDefinition( [0X[3Xinfo[0X[2X ) __________________________________[0Xfunction
  [2X> ScriptFromString( [0X[3Xstring[0X[2X ) _______________________________________[0Xfunction
  
  Let  [3Xinfo[0m  be  a  record  that  is  valid as value of [2XStandardGeneratorsInfo[0m
  ([14X1.5-1[0m).   [2XHumanReadableDefinition[0m  returns  a  string  that  describes  the
  definition  of  standard generators given by the [10Xscript[0m component of [3Xinfo[0m in
  human  readable  form.  The  names  of  the  generators  are  taken from the
  [10Xgenerators[0m   component   (default   names  [10X"a"[0m,  [10X"b"[0m  etc. are  computed  if
  necessary), and the result is stored in the [10Xdescription[0m component.
  
  [2XScriptFromString[0m  does  the  converse  of  [2XHumanReadableDefinition[0m, i.e., it
  takes  a string [3Xstring[0m as returned by [2XHumanReadableDefinition[0m, and returns a
  corresponding [10Xscript[0m list.
  
  If   "condition"  lines  occur  in  the  script  (see [2XStandardGeneratorsInfo[0m
  ([14X1.5-1[0m))   then   the   functions   that   occur   must   be   contained  in
  [2XStandardGeneratorsFunctions[0m ([14X1.5-3[0m).
  
  [4X---------------------------  Example  ----------------------------[0X
    [4Xgap> scr:= ScriptFromString( "|a|=2, |b|=3, |C(b)|=9, |ab|=13, |ababb|=4" );[0X
    [4X[ [ 1, 2 ], [ 2, 3 ], [ [ 2, 1 ], [ "|C(",, ")|" ], 9 ], [ 1, 1, 2, 1, 13 ], [0X
    [4X  [ 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 4 ] ][0X
    [4Xgap> info:= rec( script:= scr );[0X
    [4Xrec( script := [ [ 1, 2 ], [ 2, 3 ], [ [ 2, 1 ], [ "|C(",, ")|" ], 9 ], [0X
    [4X      [ 1, 1, 2, 1, 13 ], [ 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 4 ] ] )[0X
    [4Xgap> HumanReadableDefinition( info );[0X
    [4X"|a|=2, |b|=3, |C(b)|=9, |ab|=13, |ababb|=4"[0X
    [4Xgap> info;[0X
    [4Xrec( description := "|a|=2, |b|=3, |C(b)|=9, |ab|=13, |ababb|=4", [0X
    [4X  generators := "a, b", [0X
    [4X  script := [ [ 1, 2 ], [ 2, 3 ], [ [ 2, 1 ], [ "|C(",, ")|" ], 9 ], [0X
    [4X      [ 1, 1, 2, 1, 13 ], [ 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 4 ] ] )[0X
  [4X------------------------------------------------------------------[0X
  
  [1X1.5-3 StandardGeneratorsFunctions[0m
  
  [2X> StandardGeneratorsFunctions________________________________[0Xglobal variable
  
  [2XStandardGeneratorsFunctions[0m  is  a  list of even length. At position 2i-1, a
  function  of two arguments is stored, which are expected to be a group and a
  group  element.  At  position 2i a list of strings is stored such that first
  inserting  a  generator name in all holes and then forming the concatenation
  yields  a  string that describes the function at the previous position; this
  string must contain the generator enclosed in round brackets [10X([0m and [10X)[0m.
  
  This   list  is  used  by  the  functions  [2XStandardGeneratorsInfo[0m  ([14X1.5-1[0m)),
  [2XHumanReadableDefinition[0m ([14X1.5-2[0m), and [2XScriptFromString[0m ([14X1.5-2[0m). Note that the
  lists at even positions must be pairwise different.
  
  [4X---------------------------  Example  ----------------------------[0X
    [4Xgap> StandardGeneratorsFunctions{ [ 1, 2 ] };[0X
    [4X[ function( G, g ) ... end, [ "|C(",, ")|" ] ][0X
  [4X------------------------------------------------------------------[0X
  
  [1X1.5-4 IsStandardGeneratorsOfGroup[0m
  
  [2X> IsStandardGeneratorsOfGroup( [0X[3Xinfo, G, gens[0X[2X ) _____________________[0Xfunction
  
  Let  [3Xinfo[0m  be  a  record  that  is  valid as value of [2XStandardGeneratorsInfo[0m
  ([14X1.5-1[0m),  [3XG[0m  a  group,  and  [3Xgens[0m  a list of generators for [3XG[0m. In this case,
  [2XIsStandardGeneratorsOfGroup[0m returns [9Xtrue[0m if [3Xgens[0m satisfies the conditions of
  the [10Xscript[0m component of [3Xinfo[0m, and [9Xfalse[0m otherwise.
  
  Note  that  the result [9Xtrue[0m means that [3Xgens[0m is a list of standard generators
  for  [3XG[0m  only if [3XG[0m has the isomorphism type for which [3Xinfo[0m describes standard
  generators.
  
  [1X1.5-5 StandardGeneratorsOfGroup[0m
  
  [2X> StandardGeneratorsOfGroup( [0X[3Xinfo, G[, randfunc][0X[2X ) _________________[0Xfunction
  
  Let  [3Xinfo[0m  be  a  record  that  is  valid as value of [2XStandardGeneratorsInfo[0m
  ([14X1.5-1[0m),  and  [3XG[0m  a  group  of the isomorphism type for which [3Xinfo[0m describes
  standard  generators. In this case, [2XStandardGeneratorsOfGroup[0m returns a list
  of standard generators of [3XG[0m, see Section [14X1.5[0m.
  
  The optional argument [3Xrandfunc[0m must be a function that returns an element of
  [3XG[0m when called with [3XG[0m; the default is [2XPseudoRandom[0m ([14XReference: PseudoRandom[0m).
  
  In      each      call      to     [2XStandardGeneratorsOfGroup[0m     ([14XReference:
  StandardGeneratorsOfGroup[0m),  the [10Xscript[0m component of [3Xinfo[0m is scanned line by
  line. [3Xrandfunc[0m is used to find an element of the prescribed order whenever a
  definition  line  is  met,  and  for the relation and condition lines in the
  [10Xscript[0m list, the current generator candidates are checked; if a condition is
  not  fulfilled,  all  candidates  are  thrown away, and the procedure starts
  again  with  the  first  line.  When  the  conditions  are  fulfilled  after
  processing  the  last  line  of the [10Xscript[0m list, the standard generators are
  returned.
  
  Note that if [3XG[0m has the wrong isomorphism type then [2XStandardGeneratorsOfGroup[0m
  ([14XReference:  StandardGeneratorsOfGroup[0m) returns a list of elements in [3XG[0m that
  satisfy  the  conditions  of  the  [10Xscript[0m component of [3Xinfo[0m if such elements
  exist,  and  does not terminate otherwise. In the former case, obviously the
  returned elements need not be standard generators of [3XG[0m.
  
  [4X---------------------------  Example  ----------------------------[0X
    [4Xgap> a5:= AlternatingGroup( 5 );[0X
    [4XAlt( [ 1 .. 5 ] )[0X
    [4Xgap> info:= StandardGeneratorsInfo( TableOfMarks( "A5" ) )[1];[0X
    [4Xrec( ATLAS := true, description := "|a|=2, |b|=3, |ab|=5", [0X
    [4X  generators := "a, b", script := [ [ 1, 2 ], [ 2, 3 ], [ 1, 1, 2, 1, 5 ] ] )[0X
    [4Xgap> IsStandardGeneratorsOfGroup( info, a5, [ (1,3)(2,4), (3,4,5) ] );[0X
    [4Xtrue[0X
    [4Xgap> IsStandardGeneratorsOfGroup( info, a5, [ (1,3)(2,4), (1,2,3) ] );[0X
    [4Xfalse[0X
    [4Xgap> s5:= SymmetricGroup( 5 );;[0X
    [4Xgap> RepresentativeAction( s5, [ (1,3)(2,4), (3,4,5) ], [0X
    [4X>        StandardGeneratorsOfGroup( info, a5 ), OnPairs ) <> fail;[0X
    [4Xtrue[0X
  [4X------------------------------------------------------------------[0X
  
  [1X1.5-6 StandardGeneratorsInfo[0m
  
  [2X> StandardGeneratorsInfo( [0X[3Xtom[0X[2X ) ___________________________________[0Xattribute
  
  For  a  table  of  marks  [3Xtom[0m,  a  stored  value  of  [2XStandardGeneratorsInfo[0m
  ([14XReference:  StandardGeneratorsInfo!for tables of marks[0m) equals the value of
  this  attribute  for  the  underlying group (see [2XUnderlyingGroup[0m ([14XReference:
  UnderlyingGroup!for   tables  of  marks[0m))  of  [3Xtom[0m,  cf. Section [14X'Reference:
  Standard Generators of Groups'[0m.
  
  In  this case, the [2XGeneratorsOfGroup[0m ([14XReference: GeneratorsOfGroup[0m) value of
  the  underlying  group  G of [3Xtom[0m is assumed to be in fact a list of standard
  generators   for   G;   So   one   should   be   careful  when  setting  the
  [2XStandardGeneratorsInfo[0m value by hand.
  
  There  is no default method to compute the [2XStandardGeneratorsInfo[0m value of a
  table of marks if it is not yet stored.
  
  [4X---------------------------  Example  ----------------------------[0X
    [4Xgap> std:= StandardGeneratorsInfo( a5 );[0X
    [4X[ rec( ATLAS := true, description := "|a|=2, |b|=3, |ab|=5",[0X
    [4X      generators := "a, b", script := [ [ 1, 2 ], [ 2, 3 ], [ 1, 1, 2, 1, 5 ][0X
    [4X         ] ) ][0X
    [4Xgap> # Now find standard generators of an isomorphic group.[0X
    [4Xgap> g:= SL(2,4);;[0X
    [4Xgap> repeat[0X
    [4X>   x:= PseudoRandom( g );[0X
    [4X> until Order( x ) = 2;[0X
    [4Xgap> repeat  [0X
    [4X>   y:= PseudoRandom( g );[0X
    [4X> until Order( y ) = 3 and Order( x*y ) = 5;[0X
    [4Xgap> # Compute a representative w.r.t. these generators.[0X
    [4Xgap> RepresentativeTomByGenerators( a5, 4, [ x, y ] );[0X
    [4XGroup([ [ [ 0*Z(2), Z(2)^0 ], [ Z(2)^0, 0*Z(2) ] ],[0X
    [4X  [ [ Z(2^2), Z(2^2)^2 ], [ Z(2^2)^2, Z(2^2) ] ] ])[0X
    [4Xgap> # Show that the new generators are really good.[0X
    [4Xgap> grp:= UnderlyingGroup( a5 );;[0X
    [4Xgap> iso:= GroupGeneralMappingByImages( grp, g,[0X
    [4X>              GeneratorsOfGroup( grp ), [ x, y ] );;[0X
    [4Xgap> IsGroupHomomorphism( iso );[0X
    [4Xtrue[0X
    [4Xgap> IsBijective( iso );[0X
    [4Xtrue[0X
  [4X------------------------------------------------------------------[0X
  
