Setting node positions from C++ -- how to pass two values?

[Szabolcs Horvat <szhorvat AT nd.edu>]

Hello,

How can I set node positions ("xy" attribute) using NetStream (C++ API)?

According to the docs [1], I have to "pass two float values".  As far as I 
can tell, the C++ API allows only for passing a single value.  Is it possible 
to still set "xy" or "xyz" from C++?  If yes, how does the 
.addNodeAttribute() member function expect me to package the two (three) 
values together?

Szabolcs

[1] 
http://graphstream-project.org/doc/FAQ/Attributes/Is-there-a-list-of-attributes-with-a-predefined-meaning-for-the-graph-viewer_1.0/