Re: [boost] [date_time] quarters as new durations?

Subject: Re: [boost] [date_time] quarters as new durations?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-12-22 08:27:22

Jeff Garland wrote:
> Stewart, Robert wrote:
> > Thomas Lemm wrote:
> >> I am happily using the boost date_time library and I plan to
> >> extend it towards including quarters as new (gregorian) date
> >> durations, just the way months are included already
> >> (excluding parsing of quarters)
> >
> > Why excluding parsing?  That would imply only partial
> > support relative to other durations, right?
> >
> Well, so quarters turns out to be like months as far as
> durations go -- that is, it's mathematical like days and
> weeks. So the big drawback you face is dealing with the
> associated "fuzzy math".  For example, what's the result
> of
>
>    date("2008-Feb-28") + quarters(1) = ?
>    date("2008-Feb-27") + quarters(1) = ?
>
> Month durations play some games to handle this problem (see
> docs for details) which quarters could adopt.  But if you
> adopt the month rules then I don't thing you buy much more
> than simply writing
>
>    const months quarters = months(3);

That's an excellent point.  I don't think the fuzzy math approach is appropriate for quarters because they have a precise definition: 1/4 of a year.  Months are less precise, though 365 / 4 is not a whole number, of course.

There is probably still a need to use some fuzzy math in order to determine the calendar date for quarter boundaries.  Quarters are usually associated with a fiscal year and there are different definitions of those, so you probably need to add fiscal year support and make quarters a derived concept.

> There's also an argument against adding quarters as a
> duration.  I have an app somewhere in which I have quarter
> defined as a date_period so I could write:
>
>     date_period q = quarter(2009, 1);
>
> To me at least this seems like the more likely application.

I agree.  I didn't consider the ramifications of duration versus period.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

IMPORTANT: The information contained in this email and/or its attachments is confidential. If you are not the intended recipient, please notify the sender immediately by reply and immediately delete this message and all its attachments. Any review, use, reproduction, disclosure or dissemination of this message or any attachment by an unintended recipient is strictly prohibited. Neither this message nor any attachment is intended as or should be construed as an offer, solicitation or recommendation to buy or sell any security or other financial instrument. Neither the sender, his or her employer nor any of their respective affiliates makes any warranties as to the completeness or accuracy of any of the information contained herein or that this message or any of its attachments is free of viruses.