Steve Downey:
> I'd also like to see the unicode algorithms as _algorithms_ that can
> operate over something that can be treated as a scalar value.

My plan is to propose

std::unicode::scalar_value_sequence
std::unicode::grapheme_cluster_sequence

These are container adaptors that take code unit sequence (can be
std::vector, can be std::basic_string or can be
std::unicode::code_unit_sequence that I'm about to propose too).

Suddenly all standard algorithms are working with scalar values and
grapheme clusters.