From 541469371a6a95cb45cc608cf96a936282dfb76f Mon Sep 17 00:00:00 2001
From: primo-ppcg <mike.tryczak@gmail.com>
Date: Fri, 8 Sep 2023 11:35:37 +0700
Subject: [PATCH] update `mean`

---
 src/boot/boot.janet | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/boot/boot.janet b/src/boot/boot.janet
index 93a2a393..0b7c0cb4 100644
--- a/src/boot/boot.janet
+++ b/src/boot/boot.janet
@@ -643,7 +643,12 @@
 (defn mean
   "Returns the mean of xs. If empty, returns NaN."
   [xs]
-  (/ (sum xs) (length xs)))
+  (if (lengthable? xs)
+    (/ (sum xs) (length xs))
+    (do
+      (var [accum total] [0 0])
+      (each x xs (+= accum x) (++ total))
+      (/ accum total))))
 
 (defn product
   "Returns the product of xs. If xs is empty, returns 1."