Re: std::list wrapper (+templates)
isliguezze@gmail.com wrote:
template <class T>
class List {
public:
List();
List(const List&);
List(int, const T&);
void push_back(const T &);
void push_front(const T &);
void pop_back();
void pop_front();
void remove(const T &);
int size();
friend std::ostream &operator<<(std::ostream &out, const List<T> &);
I am not sure (friend declarations inside templates always confuse me)
but doesn't this declaration introduce a NON-template operator<<
function into the circulation?
private:
std::list<T> *lst;
};
template <class T>
List<T>::List() { lst = new std::list<T>(); }
template <class T>
List<T>::List(const List &rhs) { lst = new std::list<T>(rhs.lst); }
template <class T>
List<T>::List(int n, const T& value) { lst = new std::list<T>(n,
value); }
template <class T>
void List<T>::push_back(const T& value) { lst->push_back(value); }
template <class T>
void List<T>::push_front(const T& value) { lst->push_front(value); }
template <class T>
void List<T>::pop_back() { lst->pop_back; }
template <class T>
void List<T>::pop_front() { lst->pop_front; }
template <class T>
void List<T>::remove(const T& value) { lst->remove(value); }
template <class T>
int List<T>::size() { return (int)lst->size; }
template <class T>
std::ostream &operator<<(std::ostream &out, const List<T> &L)
{
for (std::list<T>::iterator it = L.lst->begin(); it != L.lst->end(); +
+it)
out << " " << *it;
out << std::endl;
return out;
}
int main()
{
List<int> il;
for (int i = 0; i < 10; ++i)
il.push_back(i);
std::cout << il;
return 0;
}
There's a crazy problem with operator>> MSVS6 says that 'lst' is
undeclared... I'm astounded... GNU G++ says that 'it' (the iterator in
operator>>) is not declared in this scope..
Well, MSVC6 is notoriously bad when it comes to templates. Download and
use their latest (2008) version, Express Edition. As for G++, it's
completely correct, 'std::list<T>::iterator' is not a type, you have to
tell the compiler that it's a type by means of 'typename' keyword:
for( typename std::list<T>::iterator it ...
V
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