code: func _round(x float64) float64 {
  	// Round is a faster implementation of:
  	//
  	// func Round(x float64) float64 {
  	//   t := Trunc(x)
  	//   if Abs(x-t) >= 0.5 {
  	//     return t + Copysign(1, x)
  	//   }
  	//   return t
  	// }
  	const (
  		signMask = 1 << 63
  		fracMask = 1<<shift - 1
  		half     = 1 << (shift - 1)
  		one      = bias << shift
  	)
  
  	bits := math.Float64bits(x)
  	e := uint(bits>>shift) & mask
  	if e < bias {
  		// Round abs(x) < 1 including denormals.
  		bits &= signMask // +-0
  		if e == bias-1 {
  			bits |= one // +-1
  		}
  	} else if e < bias+shift {
  		// Round any abs(x) >= 1 containing a fractional component [0,1).
  		//
  		// Numbers with larger exponents are returned unchanged since they
  		// must be either an integer, infinity, or NaN.
  		e -= bias
  		bits += half >> e
  		bits &^= fracMask >> e
  	}
  	return math.Float64frombits(bits)
  }
docs: // Round returns the nearest integer, rounding half away from zero.
  //
  // Special cases are:
  //	Round(±0) = ±0
  //	Round(±Inf) = ±Inf
  //	Round(NaN) = NaN