[phobos] datetime review

[Andrei Alexandrescu]

On 10/14/10 17:01 CDT, Jonathan M Davis wrote:
> What's really annoying is when you want to create a range which iterates over
> time points which are apart by some combination of years, months, and smaller
> units.

The more I think of it the more I want this feature out. It would be 
borderline nice if it were a natural consequence of the design, but 
sweating over it doesn't sit well at all.

> Before, you could just give the function something like Dur.years(5) +
> Dur.months(1) + Dur.days(2) and it would produce a function which gave you a
> time point 5 years, 1 month, and 2 days after the previous one. But without
> MonthDuration or JointDuration, that becomes much more awkward. I'm still
> ironing out the best way to deal with the function signature for that.

I could say

d.addYear(5);
d.addMonths(1);
d.addDays(2);

This is acceptable considering that it's not that often you really need 
to be 5 years, 1 month, and 2 days from now. Besides it's weird. What if 
I take 27 January 2010 and then skip that duration? Will I be on Feb 28 
2015 or Mar 1 2015? I don't know, and the simple fact that I need to ask 
myself (and that the library needs to respond) such an awkard question 
is embarrassing.

If it were me I'd even postulate that addMonths takes you to the 1st of 
the landing month. Or eliminate addMonths and addYears altogether, 
because adding 1 year to 29 February 2008 does not land on a good date. 
Allow the user to construct a new Date from the current year, month, and 
day.


Andrei