Re: [Haskell-cafe] When does the UNPACK pragma work?

On Friday 28 October 2011, 11:41:15, Eugene Kirpichov wrote:

newtype Day = ModifiedJulianDay {toModifiedJulianDay :: Integer} newtype DiffTime = MkDiffTime Pico

And Pico is also essentially a newtype for Integer.

So, I'm getting warnings on this definition of UTCTime. QUESTION: Is it the case that I can only UNPACK primitive fields, and not even their newtypes?

The problem is that you can't {-# UNPACK #-} Integer. You can only unpack single-constructor types.