As is usual with domain errors in Scheme, "it is an error", which means the implementation can do whatever it wants, just as it can with (car 1). Some possibilities might be to signal an error, to return #f or some other random value, to crash the program, or to make demons fly out of your nose.  See <http://catb.org/jargon/html/N/nasal-demons.html>.

Yes.  I'll be sending Art an amended version, hopefully today.

John Cowan          http://vrici.lojban.org/~cowan        xxxxxx@ccil.org
It's like if you meet a really old, really rich guy covered in liver
spots and breathing with an oxygen tank, and you say, "I want to be
rich, too, so I'm going to start walking with a cane and I'm going to
act crotchety and I'm going to get liver disease. --Wil Shipley