1 files changed, 132 insertions, 0 deletions
diff --git a/main/src/core/Mono.Texteditor/Mono.TextEditor.Utils/ImmutableStack.cs b/main/src/core/Mono.Texteditor/Mono.TextEditor.Utils/ImmutableStack.cs
new file mode 100644
index 0000000000..4611571c0d
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+++ b/main/src/core/Mono.Texteditor/Mono.TextEditor.Utils/ImmutableStack.cs
@@ -0,0 +1,132 @@
+// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text;
+
+namespace Mono.TextEditor.Utils
+{
+	/// <summary>
+	/// An immutable stack.
+	/// 
+	/// Using 'foreach' on the stack will return the items from top to bottom (in the order they would be popped).
+	/// </summary>
+	[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1710:IdentifiersShouldHaveCorrectSuffix")]
+	[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1711:IdentifiersShouldNotHaveIncorrectSuffix")]
+	[Serializable]
+	public sealed class ImmutableStack<T> : IEnumerable<T>
+	{
+		/// <summary>
+		/// Gets the empty stack instance.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes", Justification = "ImmutableStack is immutable")]
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1000:DoNotDeclareStaticMembersOnGenericTypes")]
+		public static readonly ImmutableStack<T> Empty = new ImmutableStack<T>();
+
+		readonly T value;
+		readonly ImmutableStack<T> next;
+
+		private ImmutableStack()
+		{
+		}
+
+		private ImmutableStack(T value, ImmutableStack<T> next)
+		{
+			this.value = value;
+			this.next = next;
+		}
+
+		/// <summary>
+		/// Pushes an item on the stack. This does not modify the stack itself, but returns a new
+		/// one with the value pushed.
+		/// </summary>
+		public ImmutableStack<T> Push(T item)
+		{
+			return new ImmutableStack<T>(item, this);
+		}
+
+		/// <summary>
+		/// Gets the item on the top of the stack.
+		/// </summary>
+		/// <exception cref="InvalidOperationException">The stack is empty.</exception>
+		public T Peek()
+		{
+			if (IsEmpty)
+				throw new InvalidOperationException("Operation not valid on empty stack.");
+			return value;
+		}
+
+		/// <summary>
+		/// Gets the item on the top of the stack.
+		/// Returns <c>default(T)</c> if the stack is empty.
+		/// </summary>
+		public T PeekOrDefault()
+		{
+			return value;
+		}
+
+		/// <summary>
+		/// Gets the stack with the top item removed.
+		/// </summary>
+		/// <exception cref="InvalidOperationException">The stack is empty.</exception>
+		public ImmutableStack<T> Pop()
+		{
+			if (IsEmpty)
+				throw new InvalidOperationException("Operation not valid on empty stack.");
+			return next;
+		}
+
+		/// <summary>
+		/// Gets if this stack is empty.
+		/// </summary>
+		public bool IsEmpty {
+			get { return next == null; }
+		}
+
+		/// <summary>
+		/// Gets an enumerator that iterates through the stack top-to-bottom.
+		/// </summary>
+		public IEnumerator<T> GetEnumerator()
+		{
+			ImmutableStack<T> t = this;
+			while (!t.IsEmpty) {
+				yield return t.value;
+				t = t.next;
+			}
+		}
+
+		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
+		{
+			return this.GetEnumerator();
+		}
+
+		/// <inheritdoc/>
+		public override string ToString()
+		{
+			StringBuilder b = new StringBuilder("[Stack");
+			foreach (T val in this) {
+				b.Append(' ');
+				b.Append(val);
+			}
+			b.Append(']');
+			return b.ToString();
+		}
+	}
+}
+\ No newline at end of file