let R be the TRS under consideration

U11(tt) -> snd(splitAt(_1,_2)) is in elim_R(R)
let l be the left-hand side and r be the right-hand side of this rule
let p = 0.0
let theta = {_1/U11(tt)}
let theta' = {}
we have r|p = _1 and
theta'(theta(l)) = theta(r|p)
so, theta(l) = U11(tt) is non-terminating w.r.t. R

Termination disproved by the backward process
proof stopped at iteration i=0, depth k=0
1 rule(s) generated