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

Subject: Re: [boost] [gsoc 2013] draft proposal for chrono::date
From: Anurag Kalia (anurag.kalia_at_[hidden])
Date: 2013-05-04 11:57:54

> Just to be sure I'm not trying to solve an issue that doesn't needs to 
> be solved:
> Given
> 
>    date d = day(33) / month(5) / 2013;
> 
> Note that I has a typo on the day. This is equivalent on my 
> implementation to
> 
> date d(year(2013), month(5), day(33));
> 
> If I want to throw a bad date exception I would need to check that the 
> day/month and year are in range. Next follows the code:
> 
>      days_date::days_date(year y, month m, day d)
>      {
>        if (set_if_valid_date(y, m, d))
>          return;
>        throw bad_date("day " + to_string(d) + " is out of range for "
>            + to_string(y) + '-' + to_string(m));
>      }
> 
>      bool days_date::set_if_valid_date(year y, month m, day d) noexcept
>      {
>        // [0]
>        bool leap = is_leap(y.value()); // [1]
>        const day_of_year::rep* year_data = days_in_year_before(leap);
> 
>        if (!(d.value() <= year_data[m.value()] - 
> year_data[m.value()-1])) // [2]
>        {
>          return false;
>        }
>        year::rep by = y.value() + 32799; // [3]
>        x_ = days_before_year(by) + year_data[m.value()-1] + d.value(); 
> // [4]
>        return true;
>      }

I have a question here. Why are we not throwing the exception from
set_if_valid_date() itself? Why did we include noexcept in its definition?

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