diff options
Diffstat (limited to 'src/Util/ListUtil.v')
-rw-r--r-- | src/Util/ListUtil.v | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/src/Util/ListUtil.v b/src/Util/ListUtil.v index cbd7bd58c..9a9ce9a06 100644 --- a/src/Util/ListUtil.v +++ b/src/Util/ListUtil.v @@ -616,3 +616,12 @@ Proof. apply IHxs. omega. Qed. + +Lemma set_nth_nth_default : forall {A} (d:A) n x l i, (0 <= i < length l)%nat -> + nth_default d (set_nth n x l) i = + if (eq_nat_dec i n) then x else nth_default d l i. +Proof. + induction n; (destruct l; [intros; simpl in *; omega | ]); simpl; + destruct i; break_if; try omega; intros; try apply nth_default_cons; + rewrite !nth_default_cons_S, ?IHn; try break_if; omega || reflexivity. +Qed.
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