/// <summary>
/// Helper for registering a plus operator.
/// </summary>
/// <param name="left">The type on the left side.</param>
/// <param name="right">The type on the right side.</param>
/// <param name="add">The function to execute.</param>
protected static void RegisterPlus(Type left, Type right, Func <Value, Value, Value> add)
{
PlusOperator.Register(left, right, add);
}