code: func _float64(i interface{}) (float64, bool) {
  
  	switch v := i.(type) {
  
  	case float32:
  		return float64(v), true
  	case float64:
  		return v, true
  	}
  
  	return 0, false
  }
docs: // _float64 converts an interface{} to a float64 iff its native type is
  // a floating point.