On Tue 22/12/09 13:27 , "Stewart, Robert" <Robert.Stewart@sig.com> wrote:

Jeff Garland wrote:

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Stewart, Robert wrote:

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Thomas Lemm wrote:

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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.

Possibly opening a can of worms here, but a quarter in my line of work is invariably three months. If your mileage varies, then there could be a problem in providing a fully meaningful quarter duration type if people think it means different things.

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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

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. period.

The issue routinely occurs with months already though. Month durations and date_periods spanning a specific month already have to work closely with each other: date_period month_containing(date d) { return date_period(date(d.year(),d.month(),1) , months(1) ); } so it may not be a big issue.