Chaddaï Fouché schreef op 23-2-2015 om 13:20:
Note that Roelof is doing the CIS 194 Homework http://www.seas.upenn.edu/~cis194/fall14/hw/03-ADTs.pdf (the older version of fall2014, not the one currently running). This is much clearer than Roelof's description, and gives among other information an algebraic datatype to represent log messages.


--
Jedaï

Correct and Im trying to do exercise 1 of Week 2,

I have tried this solution :

-- | Main entry point to the application.
{-# OPTIONS_GHC -Wall #-}

module LogAnalysis where

import Log;
import Data.Char (isLetter, isDigit)

isValid :: [Char] -> Bool
isValid s = go (words s)
    where
      go ([a]:b:_) = isLetter a && all isDigit b
      go _         = False

parseMessage :: [Char] -> [Char]
parseMessage s = isValid s
    where
        isValid = "Geldige string"
        _       = "Ongeldige string"

-- | The main entry point.
main :: IO ()
main = do
    putStrLn $ parseMessage "I 4764 He trusts to you to set them free,"


but I see this error message :

src/LogAnalysis.hs@16:18-16:27
Couldn't match expected type ‘[Char] -> [Char]’ with actual type
[Char]
The function
isValid
is applied to one argument, but its type
[Char]
has none … In the expression: isValid s In an equation for ‘parseMessage’: parseMessage s = isValid s where isValid = "Geldige string" _ = "Ongeldige string"