Is there anyway to write the following function more elegantly?
I can see some patterns but I'm not sure how to abstract them or how to find a simpler way to write the function.
type HasRemainder = Boolean
tomorrow :: Date -> Date
tomorrow date = unsafePartial $ canonicalDate y (fst m) (fst d)
where d :: Tuple Day HasRemainder
d = case toEnum $ 1 + fromEnum (day date) of
Just v -> Tuple v false
Nothing -> Tuple (unsafePartial $ fromJust $ toEnum 1) true
m :: Tuple Month HasRemainder
m = if snd d then
case toEnum $ 1 + fromEnum (month date) of
Just v -> Tuple v false
Nothing -> Tuple (unsafePartial $ fromJust $ toEnum 1) true
else Tuple (month date) false
y :: Year
y = if snd m then
case toEnum $ 1 + fromEnum (year date) of
Just v -> v
-- use 2018 arbitrarly if the conversion from int to Date fails
Nothing -> unsafePartial $ fromJust $ toEnum 2018
else (year date)
I'd do something like this:
import Data.DateTime as DT
import Data.Maybe (maybe)
import Data.Time.Duration (Days(..))
tomorrow :: DT.Date -> DT.Date
tomorrow dt = maybe dt DT.date $ DT.adjust (Days 1.0) (DT.DateTime dt bottom)
Although it will return the input date in the unlikely event that the given date is top
(which is 31st December 275759 if I remember correctly).
There is an adjust
function for Time
and DateTime
so it's just an oversight that Date
is missing one.