boost::text::v1::at_word_break
// In header: <boost/text/word_break.hpp> template<code_point_range R, word_prop_func WordPropFunc = word_prop_callable, word_break_func WordBreakFunc = untailored_word_break> bool at_word_break(R && r, std::ranges::iterator_t< R > it, WordPropFunc const & word_prop = WordPropFunc{}, WordBreakFunc const & word_break = WordBreakFunc{});