From a1289c75dcc5382b7e9cab31958fa60965f77c27 Mon Sep 17 00:00:00 2001
From: Jason Gross <jagro@google.com>
Date: Thu, 14 Jun 2018 22:17:17 -0400
Subject: Add some lemmas and defs to ListUtil.FoldBool

---
 src/Util/ListUtil/FoldBool.v | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

(limited to 'src/Util/ListUtil')

diff --git a/src/Util/ListUtil/FoldBool.v b/src/Util/ListUtil/FoldBool.v
index fcdc6d2e6..6cfe6734a 100644
--- a/src/Util/ListUtil/FoldBool.v
+++ b/src/Util/ListUtil/FoldBool.v
@@ -1,3 +1,4 @@
+Require Import Coq.Classes.Morphisms.
 Require Import Coq.Lists.List.
 
 Lemma fold_left_orb_true ls
@@ -6,3 +7,39 @@ Proof. induction ls as [|?? IHls]; [ reflexivity | assumption ]. Qed.
 Lemma fold_left_orb_pull ls v
   : List.fold_left orb ls v = orb v (List.fold_left orb ls false).
 Proof. destruct v; [ apply fold_left_orb_true | reflexivity ]. Qed.
+
+Fixpoint fold_andb_map {A B} (f : A -> B -> bool) (ls1 : list A) (ls2 : list B)
+  : bool
+  := match ls1, ls2 with
+     | nil, nil => true
+     | nil, _ => false
+     | cons x xs, cons y ys => andb (f x y) (@fold_andb_map A B f xs ys)
+     | cons _ _, _ => false
+     end.
+Lemma fold_andb_map_map {A B C} f g ls1 ls2
+  : @fold_andb_map A B f ls1 (@List.map C _ g ls2)
+    = fold_andb_map (fun a b => f a (g b)) ls1 ls2.
+Proof. revert ls1 ls2; induction ls1, ls2; cbn; congruence. Qed.
+
+Lemma fold_andb_map_map1 {A B C} f g ls1 ls2
+  : @fold_andb_map A B f (@List.map C _ g ls1) ls2
+    = fold_andb_map (fun a b => f (g a) b) ls1 ls2.
+Proof. revert ls1 ls2; induction ls1, ls2; cbn; congruence. Qed.
+
+Lemma fold_andb_map_length A B f ls1 ls2
+      (H : @fold_andb_map A B f ls1 ls2 = true)
+  : length ls1 = length ls2.
+Proof.
+  revert ls1 ls2 H; induction ls1, ls2; cbn; intros;
+    rewrite ?Bool.andb_true_iff in *;
+    f_equal; try congruence; intuition auto.
+Qed.
+
+Global Instance fold_andb_map_Proper {A B}
+  : Proper (pointwise_relation _ (pointwise_relation _ eq) ==> eq ==> eq ==> eq) (@fold_andb_map A B).
+Proof.
+  unfold pointwise_relation.
+  intros f g H ls1 y ? ls2 z ?; subst y z.
+  revert ls2; induction ls1, ls2; cbn; try reflexivity.
+  apply f_equal2; eauto.
+Qed.
-- 
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