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Date: Sun, 1 Nov 2015 05:16:00 -0800 (PST)
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Subject: Re: A few questions
From: Laurent <lutgenl@icloud.com>
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Xref: news.eternal-september.org comp.lang.ada:28157
Date: 2015-11-01T05:16:00-08:00
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On Saturday, 31 October 2015 21:49:24 UTC+1, Dmitry A. Kazakov  wrote:

> > subtype Period is range Begin_Date .. End_Date;
> 
> 1. How is this subtype would be different from Date? 
> 
Perhaps in some declarative language where lists are an fundamental part of the language itself the compiler could be smart enough to make Period a list and fill it with dates from..to? Yeah I know mind-reading compiler and World of Fantasycraft :)

> 2. Date is not a numeric type to have ranges

Agreed

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

Nonsense :)

> > I naively thought that it could be so easy.
> 
> Yes, because it is wrong.

What? Being naive or thinking that it could/should be easy? :)
 
> > 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.

I actually mentioned the "-" only because it would spare me from having to roll my own to figure out how many days are between D1 and D2. 

But I think that it is probably not necessary at all.

> > 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.

I think getting the names done is the easiest part.

When first took a look at the log files I thought that it would be difficult to extract the informations I am looking for. But no getting some continuous dates from .. to is the real PITA.

Otherwise it would be boring.

Thanks