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// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
namespace ICSharpCode.NRefactory.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();
}
}
}
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