boost::cnv::range is a consolidation of the [begin, end)-based ranges (such as std::string) and the sentry-based ranges (such as null-terminated C-style strings). It allows universal traversal of both types of ranges with

for (auto s = range.begin(); s != range.sentry(); ++s)

without the penalty or the need for an extra traversal of the sentry-based ranges in order to find the end.

TODO