[Haskell] Help-me read file

kahl at cas.mcmaster.ca kahl at cas.mcmaster.ca
Mon Oct 18 15:44:13 EDT 2010

 > I have a file with 100 lists, with 100 ints.
 > I have to read the file and apply the map and sort functions on lists.
 > II did it to read file:
 > learquivo :: FilePath -> IO ([[Int]])
 > learquivo s = do
 >            conteudo <- readFile s
 >            return (read conteudo)
 > But now applying the sort, the error appears:
 > <interactive>:1:5:
 >    Couldn't match expected type `[a]'
 >           against inferred type `IO [[Int]]'
 > how can I fix?

You did not even say how you produced that error.

Assuming you are in GHCi, you want to do:

m <- learquivo "miarquivo"

:t m

(Think of the interactive GHCi prompt as inside a big ``do''.)

Hope this helps!


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