con std::string e char
codice:
  	std::string stringa(str, str+7); // ti prende il primo STRINGA
  	std::cout << stringa.c_str() << "\n";
con std::string e string
codice:
  	std::string str("STRINGA#stringaSTRINGA"), stringa("NULL");
  	
  	unsigned int loc = str.find_first_of("S", 0);
  	unsigned int floc = str.find_first_of("#", 0);
  	
  	if(loc != std::string::npos && floc != std::string::npos){
  	  std::string stringa(loc, floc-1);	
  	}