From 034ba56bd6e459bb7dde418eea6d921adaa557d1 Mon Sep 17 00:00:00 2001
From: Atif Aziz <code@raboof.com>
Date: Sat, 1 Apr 2023 14:28:42 +0200
Subject: [PATCH] Fix "Unfold" bug so iterations are repeatable

---
 MoreLinq.Test/UnfoldTest.cs | 13 +++++++++++++
 MoreLinq/Unfold.cs          |  4 ++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/MoreLinq.Test/UnfoldTest.cs b/MoreLinq.Test/UnfoldTest.cs
index 0f5a581cb..ef2a3ee1b 100644
--- a/MoreLinq.Test/UnfoldTest.cs
+++ b/MoreLinq.Test/UnfoldTest.cs
@@ -81,5 +81,18 @@ public void UnfoldEmptySequence()
                                                   e => e.Result);
             Assert.That(result, Is.Empty);
         }
+
+        [Test(Description = "https://github.com/morelinq/MoreLINQ/issues/990")]
+        public void UnfoldReiterationsReturnsSameResult()
+        {
+            var xs = MoreEnumerable.Unfold(1, n => (Result: n, Next: n + 1),
+                                           _ => true,
+                                           n => n.Next,
+                                           n => n.Result)
+                                   .Take(5);
+
+            xs.AssertSequenceEqual(1, 2, 3, 4, 5);
+            xs.AssertSequenceEqual(1, 2, 3, 4, 5);
+        }
     }
 }
diff --git a/MoreLinq/Unfold.cs b/MoreLinq/Unfold.cs
index c61ef9745..d6f5b8738 100644
--- a/MoreLinq/Unfold.cs
+++ b/MoreLinq/Unfold.cs
@@ -61,9 +61,9 @@ public static IEnumerable<TResult> Unfold<TState, T, TResult>(
             if (stateSelector == null) throw new ArgumentNullException(nameof(stateSelector));
             if (resultSelector == null) throw new ArgumentNullException(nameof(resultSelector));
 
-            return _(); IEnumerable<TResult> _()
+            return _(state); IEnumerable<TResult> _(TState initialState)
             {
-                while (true)
+                for (var state = initialState; ;)
                 {
                     var step = generator(state);