Re: A few questions

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Sat, 31 Oct 2015 13:29:51 -0700 (PDT), Laurent wrote:

> I need a range of Dates.
>
> So I tried this:
> 
> Begin_Date: Dates.Object; 
> End_Date: Dates.Object;
> -- Dates is a package from an earlier example in my Ada95 book. It is based on Ada.Calendars. I prefer to use
> -- Dates because I actually need only the date, I don't care/ need the hour. I also find the name "Time" for 
> -- something like "2015/10/31 21:00:00" confusing but that's just my opinion.
> 
> That doesn't work unfortunately and the compiler is right to complain:
> 
> subtype Period is range Begin_Date .. End_Date;

1. How is this subtype would be different from Date? 

2. Date is not a numeric type to have ranges

3. Date cannot be a numeric type because arithmetic operations would not
make sense: D1 + D2 is what?

> I naively thought that it could be so easy.

Yes, because it is wrong.

> I have found in Ada.Calendar a: function "-" (L,R:Time) return Duration

Similarly D1 - D2 is a Duration, not a date. Likewise you can add duration
to a date, but not a date to date.

> Is it possible to make a casting to convert my Date type in (Ada.Calendar) Time type:
> 
> Today : Ada.Calendar.Time:= Time(Date); -- or something like that.

No problem. You would have an equivalent of Year, Month, Day functions
defined for Date. Then you would call Time_Of. That is.

> So is there an existing package which generates a range of Dates from .. to?

No, but you could have an abstract iterator for dates in Ada 2012.

> PS: need this range of dates because the log files I want to read and
> extract informations from are all named like this: vba-yyyymmdd.log where
> obviously yyyymmdd is the date. The program generates a new file every
> date an stores the communication it treated in it.

See Ada.Calendar.Formatting.Image.
 
-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de