applebiz89 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
Well, because it is not defined :)
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
At this point, the following names are defined:
- testDatabase
- filmsInGivenYear
- doFilmsInGivenYear
- main
- (and names from libraries)
doFilmsInGivenYear films
main
Here you use three names:
- doFilmsInGivenYear (ok, is defined)
- films (oups, not defined)
- main (ok, is defined)
So ghc tries to figure out what you mean with films, and fails, because
it was not defined. Try using one of the defined names instead of films.
Tillmann
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