// In header: <boost/text/word_break.hpp>


template<code_point_iter I, std::sentinel_for< I > S, 
         word_prop_func WordPropFunc = word_prop_callable, 
         word_break_func WordBreakFunc = untailored_word_break> 
  bool at_word_break(I first, I it, S last, 
                     WordPropFunc const & word_prop = WordPropFunc{}, 
                     WordBreakFunc const & word_break = WordBreakFunc{});