virtual string_type do_transform(const E *first, const E *last) const;
The protected virtual member function returns an object of class string_type
whose controlled sequence is a copy of
the sequence [first, last)
. If a class derived from collate<E>
overrides do_compare
, it should also override
do_transform
to match. Put simply, two transformed strings should yield the same result, when passed to
collate::compare
, that you would get from passing the untransformed strings to compare
in the derived class.