The List Trifecta, Part 1

// This file is part of the Loyc project. Licence: LGPL
using System;
using System.Collections.Generic;
using System.Text;

namespace Loyc.Collections
{
	[Serializable]
	public class EmptyList<T> : IList<T>, IRange<T>
	{
		public static readonly EmptyList<T> Value = new EmptyList<T>();

		public int IndexOf(T item)
		{
			return -1;
		}
		public void Insert(int index, T item)
		{
			ReadOnly();
		}
		private void ReadOnly()
		{
			throw new InvalidOperationException("Collection is read-only");
		}
		public void RemoveAt(int index)
		{
			ReadOnly();
		}
		public T this[int index]
		{
			get {
				throw new IndexOutOfRangeException();
			}
			set {
				throw new IndexOutOfRangeException();
			}
		}
		public T TryGet(int index, ref bool fail)
		{
			fail = true;
			return default(T);
		}
		public void Add(T item)
		{
			ReadOnly();
		}
		public void Clear()
		{
		}
		public bool Contains(T item)
		{
			return false;
		}
		public void CopyTo(T[] array, int arrayIndex)
		{
		}
		public int Count
		{
			get { return 0; }
		}
		public bool IsReadOnly
		{
			get { return true; }
		}
		public bool Remove(T item)
		{
			return false;
		}
		public IEnumerator<T> GetEnumerator()
		{
			return EmptyEnumerator<T>.Value;
		}
		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
		{
			return EmptyEnumerator<T>.Value;
		}
		public IRange<T> Slice(int start, int count)
		{
			return this;
		}

		#region IRange<T> members

		public bool IsEmpty
		{
			get { return true; }
		}
		public T Front
		{
			get { throw new EmptySequenceException(); }
		}
		public T Back
		{
			get { throw new EmptySequenceException(); }
		}

		public T PopBack(out bool fail)
		{
			fail = true; return default(T);
		}
		public T PopFront(out bool fail)
		{
			fail = true; return default(T);
		}

		IFRange<T> ICloneable<IFRange<T>>.Clone() { return this; }
		IBRange<T> ICloneable<IBRange<T>>.Clone() { return this; }
		IRange<T> ICloneable<IRange<T>>.Clone() { return this; }
		
		#endregion
	}
}