[Haskell-cafe] Main function error

[Alexander Dunlap]

On Tue, May 12, 2009 at 9:59 AM, applebiz89 <applebiz89 at hotmail.com> wrote:
>
> I have compiled each function independently and they have compiled the only
> problem is the main function..
>
> I keep getting the error 'films not defined' and I am not sure why
>
> [code]
>
> type Title = String
> type Director = String
> type Year = Int
> type Fan = String
>
> data Film = Film Title Director Year [Fan] deriving Show
>
> -- List of films
>
> testDatabase :: [Film]
> testDatabase = [ (Film "Casino Royale" "Martin Campbell" 2006 ["Garry",
> "Dave", "Zoe"])]
>
> -- Function
>
> filmsInGivenYear :: Year -> [Film] -> [String]
> filmsInGivenYear year' films = [ title | (Film title director year fans) <-
> films, year == year']
>
> doFilmsInGivenYear :: [Film] -> IO ()
> doFilmsInGivenYear films  = do putStrLn "which year?"
>                               text <- getLine
>                               let year' = read text :: Int
>                               let answer = filmsInGivenYear year' films
>                               print answer
>
> main :: IO ()
> main = do
>         doFilmsInGivenYear films
>         main
>
> [/code]
>
> if the other functions are compiling without this error im not sure as to
> why the main function does not compile because of the films...any light on
> this?
>
> Thanks

When you say 'doFilmsInGivenYear films', where does the variable
'films' come from? It's not defined anywhere in your program. That's
what the compiler is complaining about.

Alex