Should formattedWrite take the outputrange by ref?

[Tobias Pankrath]

I want to print a tree structure and need to keep track of the 
indention for different parts of the tree. My idea was to write a 
generic wrapper for an output range that outputs tabs when it 
encounters a newline. This wrapper has internal state and if I 
want to use formattedWrite with this wrapper than state changes 
don't propagate to the calling context because by value semantics.

Short solution: I'm using a class now.  But shouldn't 
formattedWrite take it's output range by ref? Does anyone else 
have a use case for this and might this cause any problems?