Thread: std container issue (copy semantics?)

Hello,
I'm creating a money-management program, and have run into a few related problems regarding std::vector s of my objects. Let's just dump it out:
Windows Vista (on my new laptop ), Dev-C++
error-spawning lines are in red.

Code:

C:/Dev-Cpp/include/c++/3.4.2/bits/vector.tcc: In member function `transaction& transaction::operator=(const transaction&)':
C:/Dev-Cpp/include/c++/3.4.2/bits/vector.tcc:238:   instantiated from `void std::vector<_Tp, _Alloc>::_M_insert_aux(__gnu_cxx::__normal_iterator<typename _Alloc::pointer, std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp = transaction, _Alloc = std::allocator<transaction>]'
C:/Dev-Cpp/include/c++/3.4.2/bits/stl_vector.h:564:   instantiated from `void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = transaction, _Alloc = std::allocator<transaction>]'

account.cpp:17:   instantiated from here
C:/Dev-Cpp/include/c++/3.4.2/bits/vector.tcc:238: error: non-static const member `const Date transaction::date_created', can't use default assignment operator

C:/Dev-Cpp/include/c++/3.4.2/bits/stl_algo.h: In function `const _Tp& std::__median(const _Tp&, const _Tp&, const _Tp&) [with _Tp = transaction]':
C:/Dev-Cpp/include/c++/3.4.2/bits/stl_algo.h:2484:   instantiated from `void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<transaction*, std::vector<transaction, std::allocator<transaction> > >, _Size = int]'
C:/Dev-Cpp/include/c++/3.4.2/bits/stl_algo.h:2555:   instantiated from `void std::sort(_RandomAccessIterator, _RandomAccessIterator) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<transaction*, std::vector<transaction, std::allocator<transaction> > >]'
account.cpp:18:   instantiated from here
C:/Dev-Cpp/include/c++/3.4.2/bits/stl_algo.h:90: error: passing `const transaction' as `this' argument of `bool transaction::operator<(const transaction&)' discards qualifiers
C:/Dev-Cpp/include/c++/3.4.2/bits/stl_algo.h:91: error: passing `const transaction' as `this' argument of `bool transaction::operator<(const transaction&)' discards qualifiers
C:/Dev-Cpp/include/c++/3.4.2/bits/stl_algo.h:93: error: passing `const transaction' as `this' argument of `bool transaction::operator<(const transaction&)' discards qualifiers
C:/Dev-Cpp/include/c++/3.4.2/bits/stl_algo.h:97: error: passing `const transaction' as `this' argument of `bool transaction::operator<(const transaction&)' discards qualifiers
C:/Dev-Cpp/include/c++/3.4.2/bits/stl_algo.h:99: error: passing `const transaction' as `this' argument of `bool transaction::operator<(const transaction&)' discards qualifiers

Code:

double account::transact(Date date_in, const std::string & name_in, double amount_in, bool nosort)
{
       bal += amount_in;
       registry.push_back(transaction(date_in,name_in,amount_in,bal));       
       if(!nosort) std::sort(registry.begin(),registry.end());       
       return bal;
}

I think that is has to do with my operator <

Code:

bool transaction::operator< (const transaction & other) { return date < other.date; }

//..... elsewhere......

inline bool Date::operator< (const Date & x)
{
       return y == x.year() ? ( m == x.month() ? d < x.day() : m < x.month() ) : y < x.year();
       //years are not same -> compare years
       //years are the same -> (months are not same -> compare months)
       //                      (months are the same -> compare days)
}

And, finally... the involed objects.....

Code:

class Date
{
 public:
        enum Spec { today, yesterday, tomorrow };
        enum Month { jan = 1, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec };
        
        Date(Month month_in = Month(0), int day_in = 0, int year_in = 0);
        Date(Spec s);
        std::string str();
        int day() const { return d; }
        int month() const { return m; }
        int year() const { return y; }
        bool operator < (const Date & x);
 private:
         int d;
         int y;
         Month m;
};

extern Date::Month & operator--(Date::Month &m);
extern Date::Month & operator++(Date::Month &m);

Code:

class transaction
{
	public:
		transaction( const Date& date_in = Date(), const std::string& name_in = std::string(), 
                     double amount_in = 0.0,       double new_bal_in = 0.0, 
                     const Date& date_created_in = Date(Date::today) );
		~transaction() {}
		
		std::string file_rep();
		std::string display_rep();
		bool operator< (const transaction & other) { return date < other.date; }
		
        Date date;
        const Date date_created;
        std::string name;
        double amount;
        double new_bal;
};

extern std::ostream & operator << (std::ofstream & s, transaction & tran);
extern std::ostream & operator << (std::ostream & s, transaction & tran);

Code:

class account
{
	public:
		account(const std::string & name_in);
		~account();
		
		double transact(Date date_in, const std::string & name_in, double amount_in, bool nosort = false);
		std::string display(unsigned int num = 0); //shows the last num transactions.
		                                   //0 means show all.
        const std::string & name() const { return n; }
        double balance() const { return bal; }
         
	private:
        std::vector<transaction> registry;
        double bal;
        std::string n;
};

Any help would be greatly appreciated.