CODEWITHSUNDEEP
haskell
user1198582
user1198582

Reputation:

What would I need to do to be able to apply `sort` to this type?

I have this complicated type

newtype CalendarDay = MkCal (Either AvailableDay UnAvailableDay)
                           deriving (Show,Ord,Eq)

Which is made up of

newtype AvailableDay = MkAD (Text, C.Day)
                      deriving (Show,Eq,Ord)

and

newtype UnAvailableDay = MkUAD (Either ScheduledDay (C.Day, Out_Of_Office))
                          deriving (Show,Ord,Eq)

ScheduledDay looks like this

data ScheduledDay = MkSDay C.Day Product ScheduledState
                   deriving (Show,Ord,Eq)

I will have a [CalendarDay], that I want to sort by the Day that is buried in all those other types. What will I have to do to make that happen?

Upvotes: 1

Views: 103

Answers (1)

hammar
hammar

Reputation: 139840

Define a function day :: CalendarDay -> Day which extracts the day from your type. You can do this with your current types, but as I mentioned in my comments, I would recommend refactoring those first. It should then be a simple matter of doing some pattern matching to extract the Day field from your type.

Once you have this function, use sortBy from Data.List to sort using a custom comparison function. You can build one with comparing from Data.Ord, like so:

sortBy (comparing day) foo

where foo :: [CalendarDay] is your list of calendar days.

Upvotes: 3

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