customize cout

Question

How can I derive a class from cout so that, for example, writing to it

new_cout << "message";

would be equivalent to

cout << __FUNCTION__ << "message" << "end of message" << endl;

Answer 1

class Log
{
public:
    Log(const std::string &funcName)
    {
        std::cout << funcName << ": ";
    }

    template <class T>
    Log &operator<<(const T &v)
    {
        std::cout << v;
        return *this;
    }

    ~Log()
    {
        std::cout << " [end of message]" << std::endl;
    }
};

#define MAGIC_LOG Log(__FUNCTION__)

Hence:

MAGIC_LOG << "here's a message";
MAGIC_LOG << "here's one with a number: " << 5;

Answer 2

#define debug_print(message) (std::cout << __FUNCTION__ << (message) << std::endl)

This has the advantage that you can disable all debug messages at once when you're done

#define debug_print(message) ()