is_emptyniltrueis_emptyconsxlfalsehdconsxlxtlconsxllappendl1l2ifappendl1l2l1ifappendl1l2nill2ifappendl1l2consxlconsxappendll22.1appendl1l2ifappendl1l2l1ifappendl1l2consxlappendll2trueappend217ifappend330append21ifappend30cons21append21ifappend3123cons22
AProVE
3d3b40ebf1f1cc0cfb76e51606fb79299fd7ea19 rene 20120105 unpublished dirty
http://aprove.informatik.rwth-aachen.de/
John
Doe