> Excel is inherently observable since it doesn't have any hidden state
Except that it does -- even in terms of simple numerical values what you see is not necessarily the actual value, but instead the result of passing the value through a format string that can vary by cell.
Sadly, most people don't use this feature, and are content to show values using the default format, even if it results in values displayed as 12904819.23 (which might be better displayed as 12.9m or 12.90m).
Except that it does -- even in terms of simple numerical values what you see is not necessarily the actual value, but instead the result of passing the value through a format string that can vary by cell.