public static ImmutableHashSet <T> IntersectSet <T>(this ImmutableHashSet <T> set1, ImmutableHashSet <T> set2)
{
if (set1.IsEmpty || set2.IsEmpty)
{
return(ImmutableHashSet <T> .Empty);
}
else if (set1.Count == 1)
{
return(set2.Contains(set1.First()) ? set1 : ImmutableHashSet <T> .Empty);
}
else if (set2.Count == 1)
{
return(set1.Contains(set2.First()) ? set2 : ImmutableHashSet <T> .Empty);
}
var builder = PooledHashSet <T> .GetInstance();
foreach (var item in set1)
{
if (set2.Contains(item))
{
builder.Add(item);
}
}
if (builder.Count == set1.Count)
{
builder.Free();
return(set1);
}
else if (builder.Count == set2.Count)
{
builder.Free();
return(set2);
}
return(builder.ToImmutableAndFree());
}
