proposition: Lemma Halt_FRACTRAN_iff P : Halt_FRACTRAN P <-> FRACTRAN_HALTING P.
proof: Proof. destruct P as (P, n). unfold Halt_FRACTRAN. now setoid_rewrite eval_iff. Qed.
imports: List Arith Undecidability.Shared.Libs.DLW(gcd rel_iter pos vec) Undecidability.FRACTRAN.Util(prime_seq) Undecidability.FRACTRAN.FRACTRAN