code: static double powerOfTwoD(int n) {
          assert(n >= DoubleConsts.MIN_EXPONENT && n <= DoubleConsts.MAX_EXPONENT);
          return Double.longBitsToDouble((((long)n + (long)DoubleConsts.EXP_BIAS) <<
                                          (DoubleConsts.SIGNIFICAND_WIDTH-1))
                                         & DoubleConsts.EXP_BIT_MASK);
      }
docs: Returns a floating-point power of two in the normal range.