code: func (t *Tag) Float(i int) (float64, error) {
  	if t.format != FloatVal {
  		return 0, t.typeErr(FloatVal)
  	}
  	return t.floatVals[i], nil
  }
docs: // Float returns the tag's i'th value as a float. It returns an error if the
  // tag's Format is not IntVal.  It panics if i is out of range.