From 6718bbdbc6997a7f8acfa0b2622afa04179a7f53 Mon Sep 17 00:00:00 2001
From: Andreas Grois <andi@grois.info>
Date: Mon, 9 Sep 2024 08:54:44 +0200
Subject: Continue Day10 Part2

---
 Common/NonEmptyList.lean | 11 +++++++++++
 1 file changed, 11 insertions(+)
 create mode 100644 Common/NonEmptyList.lean

(limited to 'Common/NonEmptyList.lean')

diff --git a/Common/NonEmptyList.lean b/Common/NonEmptyList.lean
new file mode 100644
index 0000000..786e192
--- /dev/null
+++ b/Common/NonEmptyList.lean
@@ -0,0 +1,11 @@
+structure NonEmptyList (α : Type) where
+  head : α
+  tail : List α
+
+namespace NonEmptyList
+def toList (l : NonEmptyList α) : List α :=
+  l.head :: l.tail
+
+def ofList (l : List α) (_ : ¬l.isEmpty) : NonEmptyList α :=
+  match l with
+  | head :: tail => {head, tail}
-- 
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