MoveEnd operator

MoreLinq.Test/MoveEnd.cs

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+#region License and Terms
+// MoreLINQ - Extensions to LINQ to Objects
+// Copyright (c) 2017 Leandro F. Vieira (leandromoh). 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 System.Collections.Generic;
+    using NUnit.Framework;
+
+    [TestFixture]
+    public class MoveEndTest
+    {
+        [Test]
+        public void MoveEndEndWithNegativeFromIndex()
+        {
+            AssertThrowsArgument.OutOfRangeException("fromIndex", () =>
+                new[] { 1 }.MoveEnd(-1, 0, 0));
+        }
+
+        [Test]
+        public void MoveEndWithNegativeCount()
+        {
+            AssertThrowsArgument.OutOfRangeException("count", () =>
+                new[] { 1 }.MoveEnd(0, -1, 0));
+        }
+
+        [Test]
+        public void MoveEndWithNegativeToIndex()
+        {
+            AssertThrowsArgument.OutOfRangeException("toIndex", () =>
+                new[] { 1 }.MoveEnd(0, 0, -1));
+        }
+
+        [Test]
+        public void MoveEndIsLazy()
+        {
+            new BreakingSequence<int>().MoveEnd(0, 0, 0);
+        }
+
+        [TestCaseSource(nameof(MoveEndSource))]
+        public void MoveEnd(int length, int fromIndex, int count, int toIndex)
+        {
+            var source = Enumerable.Range(0, length);
+
+            var exclude = source.Exclude(fromIndex, count);
+            var slice = source.Slice(fromIndex, count);
+            var expectations = exclude.SkipLast(toIndex).Concat(slice).Concat(exclude.TakeLast(toIndex));
+
+            using (var test = source.AsTestingSequence())
+            {
+                var result = test.MoveEnd(fromIndex, count, toIndex);
+                Assert.That(result, Is.EquivalentTo(expectations));
+            }
+        }
+
+        public static IEnumerable<object> MoveEndSource()
+        {
+            const int length = 10;
+
+            return from index in Enumerable.Range(0, length)
+                   from count in Enumerable.Range(0, length + 1)
+                   select new TestCaseData(length, index, count, index);
+        }
+
+        [TestCaseSource(nameof(MoveEndWithSequenceShorterThanToIndexSource))]
+        public void MoveEndWithSequenceShorterThanToIndex(int length, int fromIndex, int count, int toIndex)
+        {
+            var source = Enumerable.Range(0, length);
+
+            var exclude = source.Exclude(fromIndex, count);
+            var slice = source.Slice(fromIndex, count);
+
+            var expectations = slice.Concat(exclude);
+
+            using (var test = source.AsTestingSequence())
+            {
+                var result = test.MoveEnd(fromIndex, count, toIndex);
+                Assert.That(result, Is.EquivalentTo(expectations));
+            }
+        }
+
+        public static IEnumerable<object> MoveEndWithSequenceShorterThanToIndexSource()
+        {
+            const int length = 10;
+
+            return Enumerable.Range(length, length + 5)
+                             .Select(toIndex => new TestCaseData(length, 5, 2, toIndex));
+        }
+
+        [Test]
+        public void MoveEndWithFromIndexEqualsToIndex()
+        {
+            var source = Enumerable.Range(0, 10);
+            var result = source.MoveEnd(5, 999, 5);
+
+            Assert.That(source, Is.SameAs(result));
+        }
+
+        [Test]
+        public void MoveEndWithCountEqualsZero()
+        {
+            var source = Enumerable.Range(0, 10);
+            var result = source.MoveEnd(5, 0, 999);
+
+            Assert.That(source, Is.SameAs(result));
+        }
+    }
+}

MoreLinq/MoveEnd.cs

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+#region License and Terms
+// MoreLINQ - Extensions to LINQ to Objects
+// Copyright (c) 2017 Leandro F. Vieira (leandromoh). 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
+{
+    using System;
+    using System.Collections.Generic;
+
+    static partial class MoreEnumerable
+    {
+        /// <summary>
+        /// Returns a sequence with a range of elements in the source sequence
+        /// moved to a new offset.
+        /// </summary>
+        /// <typeparam name="T">Type of the source sequence.</typeparam>
+        /// <param name="source">The source sequence.</param>
+        /// <param name="fromIndex">
+        /// The zero-based index identifying the first element in the range of
+        /// elements to move.</param>
+        /// <param name="count">The count of items to move.</param>
+        /// <param name="toIndex">
+        /// The index where the specified range will be moved.</param>
+        /// <returns>
+        /// A sequence with the specified range moved to the new position.
+        /// </returns>
+        /// <remarks>
+        /// This operator uses deferred execution and streams its results.
+        /// </remarks>
+        /// <example>
+        /// <code><![CDATA[
+        /// var result = Enumerable.Range(0, 6).Move(3, 2, 0);
+        /// ]]></code>
+        /// The <c>result</c> variable will contain <c>{ 3, 4, 0, 1, 2, 5 }</c>.
+        /// </example>
+
+        public static IEnumerable<T> MoveEnd<T>(this IEnumerable<T> source, int fromIndex, int count, int toIndex)
+        {
+            if (source == null) throw new ArgumentNullException(nameof(source));
+            if (fromIndex < 0) throw new ArgumentOutOfRangeException(nameof(fromIndex), "The source index cannot be negative.");
+            if (count < 0) throw new ArgumentOutOfRangeException(nameof(count), "Count cannot be negative.");
+            if (toIndex < 0) throw new ArgumentOutOfRangeException(nameof(toIndex), "Target index of range to move cannot be negative.");
+
+            if (toIndex == fromIndex || count == 0)
+                return source;
+
+            return _(); IEnumerable<T> _()
+            {
+                var queue = new Queue<T>(toIndex);
+                var i = -1;
+                var endIndex = fromIndex + count - 1;
+                var list = new List<T>();
+
+                foreach (var item in source)
+                {
+                    i++;
+
+                    if (fromIndex <= i && i <= endIndex)
+                    {
+                        list.Add(item);
+                        continue;
+                    }
+
+                    if (queue.Count < toIndex)
+                    {
+                        queue.Enqueue(item);
+                        continue;
+                    }
+
+                    yield return queue.Dequeue();
+                    queue.Enqueue(item);
+                }
+
+                foreach (var item in list) yield return item;
+
+                foreach (var item in queue) yield return item;
+            }
+        }
+    }
+}