Exclude: Add test, fix implementation

MoreLinq.Test/ExcludeTest.cs

@@ -1,3 +1,20 @@
+#region License and Terms
+// MoreLINQ - Extensions to LINQ to Objects
+// Copyright (c) 2008 Jonathan Skeet. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#endregion
+
 namespace MoreLinq.Test
 {
     using NUnit.Framework;
@@ -143,5 +160,14 @@ public void TestExcludeStartIndexGreaterThanSequenceLength()
 
             Assert.That(result, Is.EqualTo(sequence));
         }
+
+        [TestCase(new[] { 0, 1, 2, 3, 4, 5 }, 0, 6, ExpectedResult = new int[0])]
+        [TestCase(new[] { 0, 1, 2, 3, 4, 5 }, 2, 6, ExpectedResult = new[] { 0, 1 })]
+        [TestCase(new[] { 0, 1, 2, 3, 4, 5 }, 0, 3, ExpectedResult = new[] { 3, 4, 5 })]
+        [TestCase(new[] { 0, 1, 2, 3, 4, 5 }, 2, 3, ExpectedResult = new[] { 0, 1, 5 })]
+        public int[] TestExcludeOnKnownInput(int[] source, int startIndex, int count)
+        {
+            return source.AsTestingSequence().Exclude(startIndex, count).ToArray();
+        }
     }
 }

MoreLinq/Exclude.cs

@@ -43,18 +43,30 @@ public static IEnumerable<T> Exclude<T>(this IEnumerable<T> sequence, int startI
 
             return _(); IEnumerable<T> _()
             {
-                var index = -1;
+                var index = 0;
                 var endIndex = startIndex + count;
-                var iter = sequence.GetEnumerator();
+                using var iter = sequence.GetEnumerator();
+
                 // yield the first part of the sequence
-                while (iter.MoveNext() && ++index < startIndex)
+                for (; index < startIndex; index++)
+                {
+                    if (!iter.MoveNext())
+                        yield break;
                     yield return iter.Current;
+                }
+
                 // skip the next part (up to count items)
-                while (++index < endIndex && iter.MoveNext())
-                    continue;
+                for (; index < endIndex; index++)
+                {
+                    if (!iter.MoveNext())
+                        yield break;
+                }
+
                 // yield the remainder of the sequence
                 while (iter.MoveNext())
+                {
                     yield return iter.Current;
+                }
             }
         }
     }