Unused functions in ctbl.gi

[fingolfin]

The following functions are unused (found by looking at https://codecov.io/gh/gap-system/gap/src/master/lib/ctbl.gi), nor do they seem to be documented.

• CharacterTable_IsNilpotentNormalSubgroup
• ColumnCharacterTable
• ClassPositionsOfSolvableRadical
• CharacterTableOfNormalSubgroup

Should they be used somewhere? Documented for users? Removed? Maybe @ThomasBreuer knows more?

I also noticed that there are two methods installed for CorrespondingPermutations in lib/ctblfuns.gi, one with 2 and one with 3 args. But except for one else if clause, plus some tiny (accidental??) differences, they are identical. Perhaps it would be better to merge the two into one?

[ThomasBreuer]

• CharacterTable_IsNilpotentNormalSubgroup:
  I would tend to remove this function.
  If one is interested in the information it computes
  then one can use ClassPositionsOfFittingSubgroup and a subset check.

• ColumnCharacterTable:
  I do not think that I have introduced this function.
  Can perhaps @hulpke say something about it?

• ClassPositionsOfSolvableRadical:
  I think this should be documented, in the same section as the other ClassPositionsOf... functions
  for character tables.
  Probably the reason why I did not document this one was
  that the name of the corresponding function for groups (to which the documentation should point)
  is a bad name --RadicalGroup should better be called SolvableRadical or SolvableRadicalOfGroup.
  What do others think?

• CharacterTableOfNormalSubgroup:
  This function can be useful for character tables of central products with abelian groups.
  However, it can create a complete character table only in such situations,
  and there is no suitable GAP object representing an incomplete ordinary character table without group
  --this concept had turned out to be of no interest in GAP (or at least it would not be worth the efforts).
  Thus I would propose to change the code to return fail instead of calling Error
  when the result is not a complete character table, and to document this behavior.

• CorrespondingPermutations:
  The code related to this should better be rewritten, but I do not regard this as urgent.

I can provide a pull request that addresses the above comments if there are no objections.

[olexandr-konovalov]

@fingolfin @ThomasBreuer #2681 has been merged - just to check, is this issue fully addressed now and may be closed?

[fingolfin]

I think so