/// <summary>
/// Creates an immutable hash set based on the contents of this instance.
/// </summary>
/// <returns>An immutable set.</returns>
/// <remarks>
/// This method is an O(n) operation, and approaches O(1) time as the number of
/// actual mutations to the set since the last call to this method approaches 0.
/// </remarks>
public ImmutableHashSet <T> ToImmutable()
{
// Creating an instance of ImmutableSortedMap<T> with our root node automatically freezes our tree,
// ensuring that the returned instance is immutable. Any further mutations made to this builder
// will clone (and unfreeze) the spine of modified nodes until the next time this method is invoked.
return(_immutable ??= ImmutableHashSet <T> .Wrap(_root, _equalityComparer, _count));
}
/// <summary>
/// Returns an immutable hash set that captures the result of this mutation.
/// </summary>
/// <param name="priorSet">The prior version of the set. Used to capture the equality comparer and previous count, when applicable.</param>
/// <returns>The new collection.</returns>
internal ImmutableHashSet <T> Finalize(ImmutableHashSet <T> priorSet)
{
Requires.NotNull(priorSet, "priorSet");
int count = this.Count;
if (this.CountType == ImmutableHashSet <T> .CountType.Adjustment)
{
count += priorSet._count;
}
return(priorSet.Wrap(this.Root, count));
}
