Definition codeArityLNTF (f : nat) :=
switchPR f
(switchPR (pred f)
(switchPR (pred (pred f)) (switchPR (pred (pred (pred f))) 0 1) 2) 3)
3.

Lemma codeArityLNNFIsCorrect1 :
forall f : Functions LNN,
codeArityLNTF (codeLNTFunction f) = S (arity LNN (inr _ f)).