When I write this code, I get an error from my compiler saying that NULL is an undeclared identifier.
I've also tried setting next equal to null inside the curly brackets instead, but that has the same problem. What's the problem?Code:#ifndef DISK_H
#define DISK_H
class Disk
{
public:
Disk(int no) : number(no), next(NULL) {}
~Disk() {}
bool operator <(const Disk& rhs);
bool operator >(const Disk& rhs);
bool operator ==(int rhs);
int reveal_number()
{
return this->number;
}
private:
int number;
Disk* next;
};
#endif