half 0 0 half s 0 0 half s s x s half x lastbit 0 0 lastbit s 0 s 0 lastbit s s x lastbit x zero 0 true zero s x false conv x conviter x cons 0 nil conviter x l if zero x x l if true x l l if false x l conviter half x cons lastbit x l 2.2 conv x conviter x cons 0 nil conviter x l if zero x x l conviter x l zero x if false x l lastbit x if false x l conviter half x cons lastbit x l lastbit s s x lastbit x half s s x half x if false x l half x true conv x conviter x cons 0 nil false if false x l conviter half x cons lastbit x l conviter x l if zero x x l true Failed! NaTT certifiable-1.6