Update Array inside Array

[user471]

x :: Array (Array Int)
x = [[1,2,3]] # ix 0 <<< ix 2 .~ 11

  No type class instance was found for

    Data.Lens.Index.Index (Array (Array Int))
                          Int
                          _0

  The instance head contains unknown type variables. Consider adding a type annotation.

I created this function aix

aix :: forall a. Int -> TraversalP (Array a) a
aix n = ix n
x = [[1,2,3]] # aix 0 <<< aix 2 .~ 11

Is there any better workaround?

[garyb]

I don't think so, until we have functional dependencies. The Index class needs a a -> b fundep so that the index can be determined by the type.

[LiamGoodacre]

Can be closed now that Index has the appropriate fundep?

[garyb]

Indeed! Thanks for the reminder.