Re: [boost] [chrono/date] Unit specifiers arithmetic

Subject: Re: [boost] [chrono/date] Unit specifiers arithmetic
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-05-06 09:55:39

Le 06/05/13 15:34, Howard Hinnant a écrit :
> On May 6, 2013, at 6:31 AM, "Vicente J. Botet Escriba" <vicente.botet_at_[hidden]> wrote:
>
>> Hi,
>>
>> Moving from checked dates to unchecked ones by default and forcing to user the Unit specifiers year/month/day in any date constructor (even the unchecked ones) has some ugly consequences. Note that I was able to build an unchecked date as
>>
>> date d(2013,5,6, no_check);
>>
>> Given
>>
>>   year y;
>> month m;
>>   day d;
>>
>> the following will not compile now as the constructors expects a year but y+1 is an int.
>>
>>   date d(y+1, m, d);
>>
>> The user needs to type
>>
>>   date d(year(y+1), m, d);
>>
>> Is this what we want to provide to the user or should we add basic arithmetic on these unit specifiers?
> This is an example of where flexible ordering and implicit last unit starts to shine.  Examples from my 2011 paper:
>
>          start = mon <= jan4/(d.year()-1);
>
>          date next_start = mon <= jan4/(start.year()+1);
>
> Or translated to your example and syntax:
>
>      date d(d, m, y+1);  // works because last unit can be int
Last unit or any unit but only one?
>
> If we start adding arithmetic to the unit specifier day, it becomes indistinguishable from a duration.  Now it is possible that we could use durations as unit specifiers.
-1

Vicente