From 9c17aae35a5d8194776bc348028e78b36c023d6b Mon Sep 17 00:00:00 2001
From: Atif Aziz <code@raboof.com>
Date: Tue, 24 Jan 2023 08:41:45 +0100
Subject: [PATCH] Improve optimisation for a list source in "CountDown"

---
 MoreLinq/CountDown.cs | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/MoreLinq/CountDown.cs b/MoreLinq/CountDown.cs
index a46186a89..1f5f72dad 100644
--- a/MoreLinq/CountDown.cs
+++ b/MoreLinq/CountDown.cs
@@ -65,15 +65,11 @@ public static IEnumerable<TResult> CountDown<T, TResult>(this IEnumerable<T> sou
 
             IEnumerable<TResult> IterateList(IListLike<T> list)
             {
-                var countdown = Math.Min(count, list.Count);
+                var listCount = list.Count;
+                var countdown = Math.Min(count, listCount);
 
-                for (var i = 0; i < list.Count; i++)
-                {
-                    var cd = list.Count - i <= count
-                           ? --countdown
-                           : (int?) null;
-                    yield return resultSelector(list[i], cd);
-                }
+                for (var i = 0; i < listCount; i++)
+                    yield return resultSelector(list[i], listCount - i <= count ? --countdown : null);
             }
 
             IEnumerable<TResult> IterateCollection(int i)