Commit af7806cd authored by Felipe Cerqueira's avatar Felipe Cerqueira

Add new lemma about iter_fixpoint

parent a5f12a43
......@@ -124,6 +124,32 @@ Section Iteration.
(* We also show that any inductive property P is propagated
through the fixed-point iteration. *)
Lemma iter_fixpoint_ind:
forall max_steps x0 x,
iter_fixpoint max_steps x0 = Some x ->
forall P,
P x0 ->
(forall x, P x -> P (f x)) ->
P x.
induction max_steps; first by done.
intros x0 x SOME P P0 ALL.
move: SOME; simpl.
case EQ: (_ == _).
move: EQ => /eqP EQ.
case => SAME; subst.
by rewrite EQ; apply ALL.
intros SOME; clear EQ.
apply (IHmax_steps (f x0) x SOME P); first by apply ALL.
by apply ALL.
End BasicLemmas.
Section RelationLemmas.
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