Converting C to C++

How would I go about converting this C code to C++?

/* LIBRARY is an array of structures */
/* This function compares 'tcode' with */
/* existing codes in the array. */
/* It returns the index of the code in */
/* the LIBRARY structure if it is found. */
int findcode( LIBRARY *b, int n, char *tcode ) {
     int i;

     for( i = 0; i < n; i++ )
          if( strcmp( b[i].code, tcode ) == 0 )
               return i;

     return -1;
}

This is what I have:
(I just need to know if the code exists [ie, function returns 1] in the
class. Indeces are not necessary.)

class Book {
      private:
            std::string author;
            std::string title;
            std::string code;
            int ncopies;
            int onloan;
      public:
            Book( const std::string &auth, const std::string &tit,
const std::string &cd, int ncop, int nonloan );
            Book( const std::string &auth, const std::string &tit,
const std::string &cd, int ncop );
            const std::string &getAuthor( ) const;
            const std::string &getTitle( ) const;
            const std::string &getCode( ) const;
            int getNcopies( ) const;
            int getOnLoan( ) const;
            void Borrow( int qty );
            void nReturn( int qty );
};

typedef std::vector<Book> Library;

int findcode( Library &lib, std::string tcode ) {
     for( Library::iterator itor = lib.begin( ); itor != lib.end( );
++itor ) {
          Book &b = *itor;
          if( ( tcode.compare( b.getCode ) ) == 0 )
               return 1;
     }

     return -1;
}

However, I get this error:

37 C:\CIS\22\asn2\asn2.cpp no matching function for call to
`std::basic_string<char, std::char_traits<char>, std::allocator<char>


Something about the use of compare() in the C++ findcode()...

Help, please?