Re: How to build a string on the fly, using std::ostringstream?

Here's a cleaned up version of the code I posted last night for inline
string formatting, which has been actually tested and works. The new
format is

STR_BEGIN << "asdf" << 123 << STR_END

and can be placed in a function like f(STR_BEGIN << "x = " << x <<
STR_END);

You might ask, how is this code type safe? Can't I write:
std::cout << "asdf" << STR_END;

No, you cannot. Give it a try. This is actually my biggest reservation
about this code, because I use an evil macro hack to ensure type
safty. Specifically, there are unbalanced parens in the macro. This
forces STR_BEGIN and STR_END to always appear as a pair, and allows
you to nest them and do things like

std::cout << STR_BEGIN << "asdf" << STR_END;

which would not work right if there were no parens there.

What do you think? Is this too much of a hack? Are there edge cases
I'm missing? Is there a better way?

-Brendan Miller

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

template <typename T> class Tem****ary {
   T m_data;
   public:
   T & get() {
    return m_data;
   }
};

struct ToStr {
   static ToStr instance;
};

ToStr ToStr::instance;

#define STR_BEGIN ((Tem****ary<std::ostringstream>().get())
#define STR_END (ToStr::instance))

std::string operator <<(std::ostream& stream, ToStr ts) {
   return (static_cast<std::ostringstream&>(stream)).str();
}

void f(std::string str) {
   std::cout << str;
}

int main(int argc, char** argv) {
   // proper use.
   f(STR_BEGIN << "asdf" << 123 << STR_END);

	return 0;
}

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