ostringstream

std::cout << (dynamic_caststd::ostringstream&(std::ostringstream()<<123<<"abc")).str() << std::endl;

boost::Format

https://docs.microsoft.com/en-us/cpp/text/string-and-i-o-formatting-modern-cpp?view=vs-2019

str( format("%2% %2% %1%\n") % "world" % "hello" );