Question

I am trying to implement a ray data type using the Vector type found here: http://www.haskell.org/haskellwiki/Numeric_Haskell:_A_Vector_Tutorial#Importing_the_library

The Vector will only hold doubles, so I would like to use the Unboxed version of the Vector type.

Here is the code I am trying to compile:

module Main where

    import qualified Data.Vector.Unboxed as Vector

    data Ray = Ray Data.Vector.Unboxed Data.Vector.Unboxed

The error I get is

Not in scope: type constructor or class `Data.Vector.Unboxed'
Failed, modules loaded: none.

Answer 1

The module Data.Vector.Unboxed exports a type constructor Vector which takes as an argument the type you want to store. Since you renamed this module to Vector as well, the qualified name for this type is Vector.Vector. Assuming you want two vectors of doubles, you should therefore use it like this:

data Ray = Ray (Vector.Vector Double) (Vector.Vector Double)