Try: | main :: IO () | main = do | msgs <- testParse parse 10 "error.log" | print msgs Your plan is good. GHCi handles IO values specially, for convenience, which blurs the distinction between values which can be fed to `print` directly, and those in IO, which need to be bound as above. On 2015-02-24 at 13:48, Roelof Wobben wrote:

Hello,

According to the manual of the CIS 194 course I have to do this in GHCI :  testParse parse 10 "error.log" This to test my code.

Now my problem is that I cannot use GHCI because I use Fpcomplete. So I thought I will use main for this :

So I tried  this :

main :: IO () main = do    print  $ testParse parse 10 "error.log"

but then I see this error message :

src/LogAnalysis.hs@39:4-39:9 No instance for (Show (IO [LogMessage])) arising from a use of print … In the expression: print In a stmt of a 'do' block: print $ testParse parse 10 "error.log" In the expression: do { print $ testParse parse 10 "error.log" }

The testparse function looks like this :

-- | @testParse p n f@ tests the log file parser @p@ by running it --   on the first @n@ lines of file @f@. testParse :: (String -> [LogMessage])           -> Int           -> FilePath           -> IO [LogMessage] testParse parse n file = take n . parse <$> readFile file

Roelof

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