> > But seriously I'm willing to add it, but I don't think I've heard > > a compelling use case yet... > > I wrote a date formatting function. This function can take a datetime, > date, or time duration, and format it to text. The core however, is > implemented using datetime_t. The function implements the format > as described in Microsoft's documentation: > >http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vbaac10/html/acproFormatDate.asp
Any chance you are going to contribute this? > However, to implement format "General Date" (format letter "c"), I > need to know if the given input contains a date, a time, or a > datetime. Since the functions pretty much perform the same > thing, I have a core that implements functionality for datetime and > then I use this in the function that implements date/time separately. > > However, to implement the no time I have to query whether the time > is 0:0:0.000. This is obviously problematic, since this is a > perfectly valid time. For the date, I don't even have a "start date" to > use. So I pass the core function a bool that tells it whether to ignore > the date, and pass in an arbitrary date when I want just the time. > > It would be nicer, though, if I could just pass "not_a_date" or > "not_a_time". I could even expect the datetime function to throw > an exception if the requested format is for "month" and the > "not_a_date" was passed. Seems like there will be cases where you will want to print the 'not_a_date' value instead of throwing an exception. Without a bit more detail, however, it is unclear to me how this bears on a default constructor. You can already test a date to find out if it is not_a_date_time? > There is also a problem in serialization. A lot of serialization > systems first construct an empty struct, and then read in the > values. Doing it this way prevents serialization in those > systems of dates. Yes, this is a reasonable use case although my preference for this sort of design is for the factory to use a pre-constructed prototype object since only rarely does the default constructor do the right thing -- but it really just depends. Anyway, I'm seriously considering putting in a default constructor since their don't really see serious downsides... Jeff _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
