Section TNF.
Fixpoint list_nat_sum(ls:list nat):nat :=
match ls with
| nil => O
| h::t => h+(list_nat_sum t)
end.
Definition isHaltTrans(tr:option (Trans Σ)):nat :=
match tr with
| Some _ => 0
| None => 1
end.

Lemma isHaltTrans_0 tr:
isHaltTrans tr = 0 <-> tr <> None.