Section Move.
Variable (sig : finType) (sigX X : Type) (cX : codable sigX X) (I : Retract sigX sig).
Definition isStop  (s: sig^+) := match s with inl STOP => true | _ => false end.
Definition isStart (s: sig^+) := match s with inl START => true | _ => false end.

Lemma MoveLeft_Realise : MoveLeft ⊨ MoveLeft_Rel.