MAYBE
0.08/0.18	MAYBE
0.08/0.18	
0.08/0.18	Problem:
0.08/0.18	 sum(cons(s(n),x),cons(m,y)) -> sum(cons(n,x),cons(s(m),y))
0.08/0.18	 sum(cons(0(),x),y) -> sum(x,y)
0.08/0.18	 sum(nil(),y) -> y
0.08/0.18	 empty(nil()) -> true()
0.08/0.18	 empty(cons(n,x)) -> false()
0.08/0.18	 tail(nil()) -> nil()
0.08/0.18	 tail(cons(n,x)) -> x
0.08/0.18	 head(cons(n,x)) -> n
0.08/0.18	 weight(x) -> if(empty(x),empty(tail(x)),x)
0.08/0.18	 if(true(),b,x) -> weight_undefined_error()
0.08/0.18	 if(false(),b,x) -> if2(b,x)
0.08/0.18	 if2(true(),x) -> head(x)
0.08/0.18	 if2(false(),x) -> weight(sum(x,cons(0(),tail(tail(x)))))
0.08/0.18	
0.08/0.18	Proof:
0.08/0.18	 Open
0.08/0.19	EOF