TranslationNormalizer( S )
returns the normalizer of the space group S in the full translation
group. At present, this function is implemented only for space groups,
not for general CrystGroups. The translation normalizer TN of S may
contain a continuous subgroup C. A basis of the space of such
continuous translations is bound in TN.continuousTranslations. Since
this subgroup is not finitely generated, it is not contained in the
group generated by TN.generators. Properly speaking, the translation
normalizer is the span of TN and C together.
GAP 3.4.4