From ae564f2d20a40863246286119882e8fb25a5fd3b Mon Sep 17 00:00:00 2001
From: "O'Keefe, Colin B" <cbokeefe@hrl.com>
Date: Mon, 2 Oct 2023 10:13:34 -0700
Subject: [PATCH] Add Into (Optional :a) (List :a) instance.

---
 library/list.lisp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/library/list.lisp b/library/list.lisp
index 9f0126361..bb8cf99b5 100644
--- a/library/list.lisp
+++ b/library/list.lisp
@@ -757,6 +757,12 @@ This function is equivalent to all size-N elements of `(COMBS L)`."
                         (cl:setf current top)))
            :finally (cl:return top)))))
 
+  (define-instance (Into (Optional :a) (List :a))
+    (define (into opt)
+      (match opt
+        ((None) Nil)
+        ((Some a) (Cons a Nil)))))
+
   (define-instance (Default (List :a))
     (define (default) Nil)))