Question

Possible Duplicate:
C++ Using stringstream after << as parameter

I’ve a function like this

print(const std::string& message);

How can I wrap it at some other place, such that I can use, say

print2("some message"<<object);

this should internally call the above function.

Answer 1

Here’s a C++11 solution using variadic templates:

void print(std::string const & message);   // your original function as before

void print2(std::istringstream & iss)
{
    print(iss.str());
}

template <typename T, typename ...Rest>
void print2(std::istringstream & iss, T && t, Rest &&... rest)
{
     iss << std::forward<T>(t);
     print2(iss, std::forward<Rest>(rest)...);
}

template <typename ...Args>
void print2(Args &&... args)
{
     std::istringstream iss;
     print2(iss, std::forward<Args>(args)...);
}

Usage:

print2("Some message", x, foo, "text");

An interface with a variable number of arguments is neater and more direct than an awkward use of shift operators in the function call, since the latter requires you to create a stream object explicitly, and you’d then need to deal with the stream’s low-level rdbuf directly, and that approach wouldn’t have the original, no-argument version as a special case.