/// <summary>
/// Performs a "union" of the two sets, where all the elements
/// in both sets are present. That is, the element is included if it is in either <c>a</c> or <c>b</c>.
/// Neither this set nor the input set are modified during the operation. The return value
/// is a <c>Clone()</c> of this set with the extra elements added in.
/// </summary>
/// <param name="a">A collection of elements.</param>
/// <returns>A new <c>Set</c> containing the union of this <c>Set</c> with the specified collection.
/// Neither of the input objects is modified by the union.</returns>
public Set Union(Set a)
{
Set resultSet = (Set)this.Clone();
if (a != null)
{
resultSet.AddAll(a);
}
return(resultSet);
}
/// <summary>
/// Adds all the elements in the specified collection to the set if they are not already present.
/// </summary>
/// <param name="c">A collection of objects to add to the set.</param>
/// <returns><c>true</c> is the set changed as a result of this operation, <c>false</c> if not.</returns>
public sealed override bool AddAll(ICollection c)
{
Set temp;
lock (c.SyncRoot)
{
temp = new HybridSet(c);
}
lock (_syncRoot)
{
return(_basisSet.AddAll(temp));
}
}
