Question

I’m constructing a [CalendarDay] which looks like this

newtype CalendarDay = MKCal (Either AvailableDay UnAvailableDay) deriving Show

Right now, I am passing an intermediate data type through several filters with the intent
of constructing the [CalendarDay] once all information has been gathered. The problem is, the tuple now has become a four-value tuple. Which means it’s time to do something different.

My options appear to be one of two.

1) Construct a record holding the four values, passing that along to each filter, then construct the [CalendarDay].

2) Construct the [CalendarDay] as I go along through each filter, dispensing with the intermediate data type altogether.

Opinions welcome. I’m leaning towards option 2.

I’m going to write this up in a blog entry. Don’t have a blog, but Michael Snoyman’s site will serve until I fix that problem.

Answer 1

I’d try building up the type incrementally, replacing undefined values with their found value as it is discovered.

If relying on laziness is unappealing, you could guarantee safety by well-defined intermediate types for each stage.