Define `RC` and `RV` with mutual recursion

Now, RV is a bit of a hack:

Definition RV (k : nat) (T : Ty) (rho : tymapping) (v v' : Term) : Prop :=
  value v /\ value v' /\ RC k T rho v v'.

And we have a "converting" lemma:

Lemma RV_RC k T rho e e' :
  RC k T rho e e' <->
  (forall j (Hlt_j : j < k) e_f,
    e =[j]=> e_f ->
    exists e'_f j', e' =[j']=> e'_f /\ RV (k - j) T rho e_f e'_f
  ).

This means that:

A lot of places that use RV will have to be updated, unclear in what way
Use mutual recursion with non-structural induction on the step index k (i < k). So preferably use equation again, does it support mutual recursion?

jaccokrijnen / plutus-cert

Define `RC` and `RV` with mutual recursion #38