GAP Manual: 48.27. InitClassesCharTable

InitClassesCharTable( tbl )

returns the list of conjugacy class lengths of the character table tbl, and assigns it to the field tbl.classes; the classlengths are computed from the centralizer orders of tbl.

InitClassesCharTable is called automatically for tables that are read from the library (see CharTable) or constructed as generic character tables (see Generic Character Tables).

    gap> t:= rec( centralizers:= [ 2, 2 ], identifier:= "C2" );;
    gap> InitClassesCharTable( t ); t;
    [ 1, 1 ]
    rec(
      centralizers := [ 2, 2 ],
      identifier := "C2",
      classes := [ 1, 1 ] )