Re: [office-formula] Calculation Settings

["David A. Wheeler" <dwheeler@dwheeler.com>]

robert_weir@us.ibm.com wrote:
> Here's what I'm thinking:
> 
> We have an abstract machine that does operations on dates.  Dates, when 
> stored, are stored as ISO 8601 strings.  We also define explicit and 
> implicit ways of converting numeric data into dates.  The implict coercion 
> method has one or more parameters, one of which is the date basis.
> ...   I don't think
> we should care.  What we really need to define is the type conversion. 
> 
> If we state it along those lines (conceptually -- obviously the text would 
> need to be more fully articulated) would that do the job?

Well, they really ARE numbers.  For example, ISNUMBER() must return 
TRUE() for a date or datetime value.   I know of no spreadsheet 
applications that has a true separate date type; I believe all 
applications simply use numbers, and whether or not it's a date or time 
or datetime is simply a formatting property of a particular cell.  ODF's 
storing of the 'current cell value' as an ISO date is still very nice; 
it partly isolates spreadsheets from some of the worst nastiness of 
epoch values.

If describing the operations as a separate type would be the best way to 
express what's required, then it might still be fine to word it as a 
"separate" type, if worded carefully.  Certainly there are a lot of 
languages with such types which could be used as a model.  Of course, 
good wording is always the trick :-).  Part of the reason the current 
text is so awkward is because it's trying to work around the obvious 
problem: Some applications (intentionally) calculate 1900's leap-year 
incorrectly, while others do it correctly.

If the current text isn't as clear as it should be, then by all means, 
please, propose an alternative!

--- David A. Wheeler