With C++14 you don't need to define the format string outside functions, but it does get a little hairy. Here's a half-assed example: http://coliru.stacked-croo

With C++14 you don't need to define the format string outside functions, but it does get a little hairy. Here's a half-assed example: http://coliru.stacked-crooked.com/a/3f34563e9a85af51 http://coliru.stacked-crooked.com/a/3f34563e9a85af51