check if an item is a date

[J. Landman Gay]

On 3/17/05 6:38 AM, xbury.cs at clearstream.com wrote:

> No matter that I get weird data gathering item 3 of it... yet ANOTHER bug!
> 
> But surprise! 
> 
> put (2485694 is a date)

I don't think this is a bug. Evaluating dates is a tricky business and I 
think the engine does a pretty good job of it. We can't expect it to 
read our minds and there will always be circumstances where we have to 
work around some things.

You would probably be just as angry if "20050318" was not a date, since 
that is a very common date notation in fixed-length databases. The 
number could also be the seconds; are those not dates?

> 
> It gets worse... 1 is also a date!
> 
> So either the << is a date>> function is useless as a date checker and we 
> all must roll our own AGAIN or
> there is a bug (or dare i add sarcastically "all of the above")... 

We roll our own all the time. There are some decisions to be made about 
how dates are evaluated, and I think Rev does a much better job of it 
than HyperCard ever did. We had long discussions about date notation on 
the HC list a few years ago. Because of the differences in system dates 
(HC was distributed in dozens of different languages) the engineers on 
the HC team decided to just use pattern matching to determine dates. 
Thus in HyperCard:

put "1dog2dog3" is a date  <-- TRUE

put "1dog2cat3" is a date <-- FALSE

Revolution says neither of these are dates. I think that is better.

> 
> Is there something I missed? Can you enforce dateformat checking like you 
> would in C via type casting?

Without variable typing, which is one of the strongest advantages of Rev 
in my opinion, I don't see how the engine can do it any differently than 
it does now. It certainly does a better job than HyperCard.

> 
> The documentation was useless... Another bugzilla would delay further the 
> other bugzillas which are 
> blocking the release of 3 softwares since months... 
> 
> Any ideas other than writing YetAnotherBugDetour function?

A work-around was posted on the HC list a few years ago, you might 
search those archives.

If you can think of a bullet-proof way to evaluate dates in all 
languages, with all types of delimiters, with all types of system date 
formats, without mistaking seconds or fixed-length notations as 
non-dates, you might consider submitting a feature request with your 
suggestions.

-- 
Jacqueline Landman Gay         |     jacque at hyperactivesw.com
HyperActive Software           |     http://www.hyperactivesw.com