Ashley Yakeley
data T = Y Int | M Int T | Wy Int T | Wm Int T | Dy Int T | Dm Int T | Dw Int T | Hr Int T | Min Int T deriving (Eq,Show)
The idea is that time can be a year, or a month in some year, or a week in some year (yes, I know it's ambigous), week in month (in year), day in year, day in month in year, and so on.
This seems to be equivalent to DateTime::Incomplete in Perl's DateTime.
(That's a pretty odd name for it.)
If so I'd consider representing it more like this:
data T = MkT y :: Maybe Int m :: Maybe Int wy :: Maybe Int wm :: Maybe Int ...
Yes, that's a possibility. And of course, it is possible to leave fields undefined in a record as well. I'd like there to be a good way of using the type system to ensure that the dates are "sensible" (e.g. you don't specify both wm and wy etc), but I'm not sure how. Note that MkT is not quite similar, in my suggestion, you would need at least to specify the year to have the precise date. So if I want to specify my birthday, the natural representation would be as a function: \(Y y) -> (Dm 19 (M 5 (Y y))) Perhaps another approach, making better use of the type system, would be to say something like: data Year = Y Int data Month = M Int Year data Week = Wy Int Year | Wm Int Month data Day = Dy Int Year | Dm Int Month | Dw Int Week : data Second = S Int Hour | S Int Day -- of year, for UTC I guess I'm just rambling, and should sit down and think things through a bit. Or at least post to -cafe :-) -kzm -- If I haven't seen further, it is by standing in the footprints of giants