How to nest unboxed vectors?

Question

This may be a pretty basic question, but I've searched around and I cannot seem to find the answer.

I would like to represent a 2D list using unboxed Vectors. This is easily done with normal vectors:

> import qualified Data.Vector as V
> V.fromList [V.fromList [1..5]]
[[1,2,3,4,5]]

But if I try with unboxed vectors:

> import qualified Data.Vector.Unboxed as U
> U.fromList [U.fromList [1..5]]

I get the following error:

• Non type-variable argument
    in the constraint: U.Unbox (U.Vector a)
  (Use FlexibleContexts to permit this)
• When checking the inferred type
    it :: forall a.
          (U.Unbox (U.Vector a), U.Unbox a, Num a, Enum a) =>
          U.Vector (U.Vector a)

I suspect it has something to do with this:

> V.fromList [1..5]
[1,2,3,4,5]

whereas

> U.fromList [1..5]
[1.0,2.0,3.0,4.0,5.0]

But I can't seem to understand how to avoid this.

Thanks in advance!

How to nest unboxed vectors?

1 Answers