MAYBE

We are left with following problem, upon which TcT provides the
certificate MAYBE.

Strict Trs:
  { rev(nil()) -> nil()
  , rev(.(x, y)) -> ++(rev(y), .(x, nil()))
  , ++(nil(), y) -> y
  , ++(.(x, y), z) -> .(x, ++(y, z))
  , car(.(x, y)) -> x
  , cdr(.(x, y)) -> y
  , null(nil()) -> true()
  , null(.(x, y)) -> false() }
Obligation:
  innermost runtime complexity
Answer:
  MAYBE

The input cannot be shown compatible

Arrrr..