Require Import Undecidability.Synthetic.Definitions.
Require Import Undecidability.FRACTRAN.FRACTRAN.
From Undecidability.FRACTRAN.Deciders Require
Halt_REV_FRACTRAN_dec.
Theorem Halt_REV_FRACTRAN_dec : decidable Halt_REV_FRACTRAN.
Proof.
exists Halt_REV_FRACTRAN_dec.decide.
exact Halt_REV_FRACTRAN_dec.decide_spec.
Qed.
Check Halt_REV_FRACTRAN_dec.