Time library design proposal

Bayley, Alistair Alistair_Bayley at ldn.invesco.com
Wed Feb 2 09:44:31 EST 2005

[Oops, replied only to Ashley, not to list.]

> From: Ashley Yakeley [mailto:ashley at semantic.org] 
> There's something to be said for representing date and time of day 
> separately in calendar time, something like this:
>   data CalendarDate = CalendarDate ...
>   data TimeOfDay = TimeOfDay ...
>   data CalendarTime = CalendarTime
>   {
>     ctDate :: CalendarDate,
>     ctTime :: TimeOfDay
>   }
> On the other hand, it adds two levels of construction to CalendarTime.

I'm not convinced. I think it would be simpler and just as functional to
have just a CalendarTime and a Duration. You would represent a time by a
Duration (i.e. time since midnight), and a day with no time component would
be represented by that date at midnight. You could add a Duration to a
CalendarTime to get a date-with-time.

Durations have other uses (differences between two CalendarTimes, summing
other Durations, etc), whereas a TimeOfDay is limited to a 24hr period.


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