Set Collections for C#

// Copyright � Keith Barrett 2008.

using System;
using System.Collections.Generic;
using System.Text;
using Iesi.Collections;
using System.Collections;

namespace KMB.Library.Collections
{
    /// <summary>
    /// A value type for small sets of integers.  
    /// It uses the bits of a 16 bit integer to record membership.
    /// </summary>
    public struct SetOfInts16 : ISet
    {
        private short _bits;

        public SetOfInts16(short val)
        {
            _bits = val;
        }
        
        /// <summary>
        /// Copy constructor.
        /// </summary>
        public SetOfInts16(SetOfInts16 that)
        {
            _bits = that._bits;
        }

        #region ISet Members

        public ISet Union(ISet a)
        {
            if (a is SetOfInts16)
                return Union((SetOfInts16)a);
            else
                return new UnionSet(this, a);
        }

        public SetOfInts16 Union(SetOfInts16 a)
        {
            short newBits = (short)(this._bits | a._bits);
            return new SetOfInts16(newBits);
        }

        public ISet Intersect(ISet a)
        {
            if (a is SetOfInts16)
                return Intersect((SetOfInts16)a);
            else
                return new IntersectSet(this, a);
        }

        public SetOfInts16 Intersect(SetOfInts16 a)
        {
            short newBits = (short)(this._bits & a._bits);
            return new SetOfInts16(newBits);
        }

        public ISet Minus(ISet a)
        {
            if (a is SetOfInts16)
                return Minus((SetOfInts16)a);
            else
                return new MinusSet(this, a);
        }

        public SetOfInts16 Minus(SetOfInts16 a)
        {
            short newBits = (short)(this._bits & ~a._bits);
            return new SetOfInts16(newBits);
        }

        public ISet ExclusiveOr(ISet a)
        {
            if (a is SetOfInts16)
                return ExclusiveOr((SetOfInts16)a);
            else
                return new ExclusiveOrSet(this, a);
        }

        public SetOfInts16 ExclusiveOr(SetOfInts16 a)
        {
            short newBits = (short)(this._bits ^ a._bits);
            return new SetOfInts16(newBits);
        }

        public bool Contains(int i)
        {
            if (i < 0 || i > 15)
                return false;
            int x = (_bits & (1 << i));
            return (x != 0);
        }

        public bool Contains(object o)
        {
            if (o == null)
                return false;
            try
            {
                int i = (int)o;
                return Contains(i);
            }
            catch (Exception)
            {
                return false;
            }
        }

        public bool Set(int i, bool val)
        {
            if (i < 0 || i > 15)
               throw new Exception("range error");

            bool bOldVal = Contains(i);

            if( val )
                _bits |= (short)(1 << i);
            else
                _bits &= (short) ~(1 << i);

            return (bOldVal != val);
        }

        public void SetRange(int first, int last, bool val)
        {
            for (int i = first; i <= last; i++)
                Set(i, val);
        }

        public bool Add(int i)
        {
            return Set(i, true);
        }

        public bool Add(object o)
        {
            if (o == null)
                return false;
            try
            {
                int i = (int)o;
                return Add(i);
            }
            catch (Exception)
            {
                return false;
            }
        }

        public bool Remove(int i)
        {
            if (i < 0 || i >= 16)
                return false;
            else
                return Set(i, false);
        }

        public bool Remove(object o)
        {
            if (o == null)
                return false;
            try
            {
                int i = (int)o;
                return Remove(i);
            }
            catch (Exception)
            {
                return false;
            }
        }

        public void Clear()
        {
            _bits = 0;
        }

        #endregion

        #region ICollection Members

        int GetCount()
        {
            int total = 0;
            for (int i = 0; i < 16; i++)
            {
                if (Contains(i))
                    total++;
            }
            return total;
        }

        #endregion

        #region IEnumerable Members

        public System.Collections.IEnumerator GetEnumerator()
        {
            for(int i=0; i < 16; i++)
            {
                if( Contains(i) )
                    yield return i;
            }
        }

        #endregion

        #region ICloneable Members

        public object Clone()
        {
            return new SetOfInts16(this);
        }

        // How can I make this belong to the class type, 
        // so that set1.GetType().GetElementType() works?
        public Type GetElementType()
        {
            return typeof(int);
        }
        #endregion

        #region ISet Members


        public bool ContainsAll(ICollection c)
        {
            return Sets.ContainsAll(this, c);
        }

        public bool IsEmpty
        {
            get { return (_bits == 0); }
        }

        public bool AddAll(ICollection c)
        {
            foreach (object o in c)
            {
                if (!this.Add(o))
                    return false;
            }
            return true;
        }

        public bool RemoveAll(ICollection c)
        {
            foreach (object o in c)
            {
                if (!this.Remove(o))
                    return false;
            }
            return true;
        }

        public bool RetainAll(ICollection c)
        {
            throw new Exception("The method or operation is not implemented.");
        }

        #endregion

        #region ICollection Members

        public void CopyTo(Array array, int index)
        {
            Sets.CopyTo(this, array, index);
        }

        public int Count
        {
            get { return GetCount(); }
        }

        public bool IsSynchronized
        {
            get { throw new Exception("The method or operation is not implemented."); }
        }

        public object SyncRoot
        {
            get { throw new Exception("The method or operation is not implemented."); }
        }

        #endregion

        public override bool Equals(object o)
        {
            if (o == null)
                return false;
            if (o is SetOfInts16)
                return Equals((SetOfInts16)o);
            return false;
        }

        public bool Equals(SetOfInts16 that)
        {
            return (_bits == that._bits);
        }

        public override int GetHashCode()
        {
            return _bits.GetHashCode();
        }

        public override string ToString()
        {
            return Sets.ToString(this);
        }
    }
}