[Haskell-beginners] Re: confusion about parameterized types.

[Michael Litchard]

Okay, ski (of Freenode fame) helped me with the first problem. Now I
need to figure out how to use specific types.

given


> module Main where
> import System.Environment
> import PrepData

> data ProcessData =
>    ProcessData { flatfile :: String
>                , processfunc :: [String] -> Table StudentsOrActivities Value
>                }

> main = undefined

and

> module PrepData where
> data Value = Cost Int | ID Int
> type Tname = String
> data StudentsOrActivities = Students String | Activities String
> data Table soa v = PopTable
>       { tableName :: Tname
>       , tableColumns :: [(soa, v)]
>       } deriving (Show, Read)

> popStudents :: [String] -> Table Students ID
> popStudents flatFile = undefined

is it clear what I am trying to do in popStudents?

here's the error I get
PrepData.lhs:10:35:
    Not in scope: type constructor or class `Students'

PrepData.lhs:10:44: Not in scope: type constructor or class `ID'