public void AddLongTest()
        {
            foreach (MultiPrecision <Pow2.N8> a in vs)
            {
                foreach (long b in us)
                {
                    MultiPrecision <Pow2.N8> c_actual = MultiPrecision <Pow2.N8> .Add(a, b);

                    MultiPrecision <Pow2.N8> c_expect = MultiPrecision <Pow2.N8> .Add(a, (MultiPrecision <Pow2.N8>) b);

                    Trace.WriteLine($"{a} + {b} = {c_expect}");
                    Trace.WriteLine($"{a} + {b} = {c_actual}");

                    if (c_actual.IsNaN && c_expect.IsNaN)
                    {
                        continue;
                    }

                    if (a.IsNaN)
                    {
                        if (!c_actual.IsNaN)
                        {
                            Console.WriteLine($"{a} + {b} = {c_expect}");
                            Console.WriteLine($"{a} + {b} = {c_actual}");
                            Console.Write("\n");

                            Assert.Fail();
                        }
                    }
                    else
                    {
                        Console.WriteLine($"{a} + {b} = {c_expect}");
                        Console.WriteLine($"{a} + {b} = {c_actual}");
                        Console.Write("\n");

                        Assert.AreEqual(c_expect, c_actual);
                    }
                }
            }
        }