code: func (v *variable) stringValue() string {
  	switch v.kind {
  	case boolKind:
  		return fmt.Sprint(v.boolValue())
  	case intKind:
  		return fmt.Sprint(v.intValue())
  	case floatKind:
  		return fmt.Sprint(v.floatValue())
  	}
  	return v.value
  }
docs: // stringValue returns a canonical representation for a variable.