From: kingos@optusnet.com.au
Hi,
I am hoping to use boost::date_time to do some date calculations. What I want to do is basically work out the number of days to a given date with various exclusions applied.
eg.
How many working days are there to christmas?
using namespace boost::gregorian;
int CalculateDaysToChristmas() { date_period someHoliday(date(2006, Dec, 01), date_duration(1));
date today(2006, Sep, 1);
date christmas(2006, Dec, 25);
int days = 0; for (day_iterator i = today; i != christmas; ++i) { if (is_weekday(*i) && !someHoliday.contains(*i)) ++days; }
return days; }
However, I can't find a simply way to work out is_weekday ... Secondly, is there some way to put every sunday in as a date_period? Thirdly, this doesn't seem very optimal ... is there a better way of doing this?
First off, is_weekday is pretty simple, something like: bool is_weekday(const gregorian::date& d) { return d.day_of_week != Saturday && d.day_of_week != Sunday; } Second, I don't understand your question about Sundays. Third, you're right, it isn't very optimal. You'd be better off to note that weekdays in a period are equal to: complete weeks in the period * 5 + extra weekdays at the end of the period - holidays in the period Complete weeks in the period is easy to compute (days_between/7); the extra weekdays could be done via iterator (but guarantee to be <= 6 times through the loop) or via lookup table if you want really fast results. So this just leaves holidays in the period. It would be pretty easy to build a class which implemented a fast (constant-time) lookup for the # of holidays given a starting and ending date. Once you've got that, voila. If you're looking for some really quick way to do this in Boost::DateTime, I don't think it's possible. Holidays aren't even localizable, since different businesses in the same locale can have different holiday schedules. It might be nice to include some sort of "date-exclusion" functionality in Boost that would implement the class I propose above, but I'm not sure this would be generally useful enough to bother with. Anyone else have an opinion on this? - James Jones Administrative Data Mgmt. Webmaster 375 Raritan Center Pkwy, Suite A Data Architect Edison, NJ 08837