Re: [boost] [gsoc 2013] draft proposal for chrono::date

Subject: Re: [boost] [gsoc 2013] draft proposal for chrono::date
From: Michael Marcin (mike.marcin_at_[hidden])
Date: 2013-05-03 11:07:10

On 5/3/2013 8:30 AM, Vicente J. Botet Escriba wrote:
> Le 03/05/13 13:52, Rob Stewart a écrit :
>> On May 3, 2013, at 3:47 AM, "Vicente J. Botet Escriba"
>> <vicente.botet_at_[hidden]> wrote:
>>
>>>> You can even handle other orders that way:
>>>>
>>>> date(month, unsigned, year);
>>>> date(month, day, unsigned);
>>>> date(unsigned, day, month);
>>>> date(year, unsigned, month);
>>>>
>>>> One can also be explicit for both day and year:
>>>>
>>>> date(year, month, day);
>>>> date(month, day, year);
>>>> date(day, month, year);
>>>> date(day, year, month);
>>> I don't think that the constructor should support different orderings.
>> It could, easily, so why not? Different locales have different
>> preferred orderings. All can learn to use the descending magnitude
>> order, but a little flexibility, without ambiguity, would be nice.
>>
>>>> I'm assuming explicit constructors for day and year, of course.
>>> Of course. And implicit conversion to his representation, so that
>>>
>>>   date(2013, may, 3, no_check)
>>>
>>> is yet valid.
>> That's where I disagree. If you have explicit constructors for year
>> and day, and no constructor accepting two ::rep arguments, then your
>> example won't compile.
>>
>> That's also what enables support for other argument orders.
> The no_check constructor allows only year,month,day order of arguments.
> If the user know that the date is valid it can know the order. This is a
> low level function.
>>
>>> We could have a factory make_date function that doesn't checks the
>>> validity of the date and avoids the no_check parameter
>>>
>>>   make_ymd_date(2013, may, 3)
>> I don't understand what no_check has to do with such a function. Add
>> an overload that accepts no_check_t to get that.
>>
>>
> The name is not the good one.
>
>   make_unchecked_date(2013, may, 3);
> or
>
>   make_valid_date(2013, may, 3);
>

This reminds me of the constexpr date constructor sketched out at:

http://akrzemi1.wordpress.com/2011/05/06/compile-time-computations/