From b37fc3089eb0ca8fc37a82ae6d6071b0accbca19 Mon Sep 17 00:00:00 2001
From: Andreas Grois <andi@grois.info>
Date: Sat, 21 Dec 2024 21:37:51 +0100
Subject: Continue Day17

---
 Common/HashSet.lean | 9 +++++++++
 1 file changed, 9 insertions(+)
 create mode 100644 Common/HashSet.lean

(limited to 'Common/HashSet.lean')

diff --git a/Common/HashSet.lean b/Common/HashSet.lean
new file mode 100644
index 0000000..1845443
--- /dev/null
+++ b/Common/HashSet.lean
@@ -0,0 +1,9 @@
+import Std.Data.HashSet
+import Common.Finite
+
+open Std.HashSet
+namespace Std.HashSet
+
+theorem finite_size {α : Type u} [Finite α] [BEq α] [LawfulBEq α] [Hashable α] (set : Std.HashSet α) : set.size ≤ Finite.cardinality α := by
+
+  sorry
-- 
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