Generating random numbers

SampleArcTanh is at , the seam between the two forms of approximation. Here is a straightforward test function:

  void RandomTest(int testCount) {
      TUniformRandomDouble randomDelta;   // initialize generator
      const double_t kBand = 0x1.0p-10;   // width of test band
      const double_t kSeam = 0x1.0p-27;
      const double_t kTolerance = 1.0E-15;
      for (int i = 0; i < testCount; i++) {
          double testArg = kSeam + (randomDelta.Next() - 0.5) * kBand;
          if (ExcessiveRelativeError(
                  SampleArcTanh(testArg),
                  SlowButSureArcTanh(testArg),
                  kTolerance))
              ReportSuspiciousError(testArg);
      }
  }