YES proof: The input problem is infeasible because [1] the following set of Horn clauses is satisfiable: min(xs) = y & le(x, y) = false ==> min(cons(x, xs)) = y min(xs) = y & le(x, y) = true ==> min(cons(x, xs)) = x min(cons(x, nil)) = x le(s(x), s(y)) = le(x, y) le(0, s(y)) = true le(x, 0) = false min(nil) = x3 & le(x1, x3) = false ==> true__ = false__ true__ = false__ ==> \bottom This holds because [2] the following E does not entail the following G (Claessen-Smallbone's transformation (2018)): E: g1(false, x, xs) = min(xs) g1(le(x, min(xs)), x, xs) = min(cons(x, xs)) g1(true, x, xs) = x le(0, s(y)) = true le(s(x), s(y)) = le(x, y) le(x, 0) = false min(cons(x, nil)) = x t1(false) = false__ t1(le(x1, min(nil))) = true__ t2(false__) = true__ t2(true__) = false__ G: true__ = false__ This holds because [3] the following ground-complete ordered TRS entails E but does not entail G: g1(false, x, xs) -> min(xs) g1(le(Y0, min(nil)), Y0, nil) -> Y0 g1(true, x, xs) -> x le(0, s(y)) -> true le(s(x), s(y)) -> le(x, y) le(x, 0) -> false min(cons(x, xs)) -> g1(le(x, min(xs)), x, xs) t1(false) -> false__ t1(le(x1, min(nil))) -> true__ t2(false__) -> true__ t2(true__) -> false__ with the LPO induced by s > true > cons > le > false > nil > g1 > min > t1 > 0 > t2 > true__ > false__