boost::unicode::ucd::get_decomposition_type
// In header: <boost/unicode/ucd/properties.hpp> decomposition_type::type get_decomposition_type(char32 ch);
Hangul syllables have a canonical decomposition, but it is not present in the UCD as it can be procedurally generated. This function will thus return decomposition_type::none for those code points. See also boost::unicode::hangul_decomposer.
decomposition_type::none
boost::unicode::hangul_decomposer