CINT is really rather silly as the main interface to ROOT. ROOT is awesome, and huge, and you do need to use C++ to take full advantage of it, but it is also accessible from Python which is a far more sensible language to use in a REPL or in small scripts. I always did C++ for longer scripts or to integrate with other C/C++ work, but Python for quick scripts and REPL exploration.

Nice to see CINT evolving and using clang for better conformance (and performance, presumably), and hopefully this will free some time that was being spent on CINT but if you find yourself using this more than once for physics analysis, do yourself a favor and try python instead.