"Hmm, can you elaborate on how it manages this? Is it just printing nil, but otherwise leaving the actual cons cells ()-terminated? (That option has probably been discussed multiple times: http://arclanguage.org/item?id=3094. I'm sure I mentioned it too at some point.)"
Yes. And then "nil" is a global variable that is bound to (). I also have to do a few other things like changing quote so that it changes the symbol "nil" to (), but overall it isn't that hard to have perfect Arc compatibility, even without doing the conversion.
16 lines total. Probably less than it would have taken to do the 'nil -> () conversion. But Arc can't tell the difference, unless I've overlooked something.
