Библиотека icu - ошибка компиляции

#include <boost/regex/icu.hpp>
 
UnicodeString reg_replace(UnicodeString content_p, UnicodeString pattern_p, UnicodeString replacement_p) {
 
    boost::u32regex pattern = boost::make_u32regex(pattern_p);
    return boost::u32regex_replace(content_p, pattern, replacement_p);
 
}

UnicodeString extract_greek(const UnicodeString& text)
{
   // searches through some UTF-16 encoded text for a block encoded in Greek,
   // this expression is imperfect, but the best we can do for now - searching
   // for specific scripts is actually pretty hard to do right.
   //
   // Here we search for a character sequence that begins with a Greek letter,
   // and continues with characters that are either not-letters ( [^[:L*:]] )
   // or are characters in the Greek character block ( [\\x{370}-\\x{3FF}] ).
   //
   boost::u32regex r = boost::make_u32regex(L"[\\x{370}-\\x{3FF}](?:[^[:L*:]]|[\\x{370}-\\x{3FF}])*");
   boost::u16match what;
   if(boost::u32regex_search(text, what, r))
   {
      // extract $0 as a CString:
      return UnicodeString(what[0].first, what.length(0));
   }
   else
   {
      throw std::runtime_error("No Greek found!");
   }
}