Re: a reliable way of dropping levity args?

28 Jan 2016


      It might be nice to actually replace `drop (length args `div` 2) args` with a
function `dropLevityArgs = dropWhile (isLevityTy . typeKind)` (I did this in my
branch). When I see a code that drops half of the type arguments it doesn't
make sense right away, but `dropLevityArgs` is at least giving an idea of
what's actually happening.

2016-01-28 20:30 GMT-05:00 Ömer Sinan Ağacan :
...
Ahh, levity is type of kinds, right? For some reason I thought kinds are now
levities (or whatever it's called). This makes sense. I just tried and I think
it works, thanks.
2016-01-28 19:39 GMT-05:00 Richard Eisenberg :
...
On Jan 28, 2016, at 5:48 PM, Ömer Sinan Ağacan  wrote:
...
| Just (tc, args) <- splitTyConApp_maybe ty
   , isUnboxedTupleTyCon tc
   = pprTrace "elimUbxSumRepTypes"
       (text "orig args:" <+> ppr args $$
        text "dropWhile isLevityTy args = " <+> ppr (dropWhile
isLevityTy args)) $
     concatMap go (drop (length args `div` 2) args)
You want (dropWhile (isLevityTy . typeKind) args). isLevityTy simply checks if its argument is exactly `Levity`.
Does that work?
Richard