16.56.cpp

#include<iostream>
#include<string>
#include<sstream>

template <typename T> std::ostream & print(std::ostream & os, const T & t);
template <typename T, typename ... Args> std::ostream & print(std::ostream & os, const T & t, const Args & ... rest);
template <typename T> std::string debug_rep(const T &t);
template <typename T> std::string debug_rep(T * p);
std::string debug_rep(const std::string &s);
std::string debug_rep(char *p);
std::string debug_rep(const char *p);
template <typename ... Args> std::ostream & errorMsg(std::ostream & os, const Args & ... rest);

template <typename T>
std::ostream & print(std::ostream & os, const T & t)
{
	return os << t;
} 

template <typename T, typename ... Args>
std::ostream & print(std::ostream & os, const T & t, const Args & ... rest)
{
	os << t << ", ";
	return print(os, rest...);
}

template <typename T>
std::string debug_rep(const T &t)
{
	std::ostringstream ret;
	ret << t;
	return ret.str();
}

template <typename T>
std::string debug_rep(T * p)
{
	std::ostringstream ret;
	ret << "pointer: " << p;
	if(p)
		ret << " " << debug_rep(*p);
	else
		ret << " null pointer";
	return ret.str(); 
}

std::string debug_rep(const std::string &s)
{
	return '"' + s + '"';
}

std::string debug_rep(char *p)
{
	return debug_rep(std::string(p));
}
std::string debug_rep(const char *p)
{
	return debug_rep(std::string(p));
}

template <typename ... Args>
std::ostream & errorMsg(std::ostream & os, const Args & ... rest)
{
	return print(os, debug_rep(rest)...);
}

int main()
{
	int i = 3;
	errorMsg(std::cout, 1, "123", std::string("qwer"), &i) << std::endl;
	errorMsg(std::cout, 1) << std::endl;
	return 0;
}