[Haskell-cafe] First time haskell - parse error!

[Kyle Murphy]

Seems like a good time to mention the Maybe monad looks like it would be a
good fit here.

score :: String -> String -> Maybe String
score s [] = Nothing
score s g =
    if valid 4 g
    then let s1 = "Golds "
        s2 = show (gold s g)
        s3 = ", Silvers "
        s4 = show (silver s g)
        in Just (s1 ++ s2 ++ s3 ++ s4)
    else Just "Bad Guess"

-R. Kyle Murphy
--
Curiosity was framed, Ignorance killed the cat.


On Tue, Mar 9, 2010 at 17:42, Brent Yorgey <byorgey at seas.upenn.edu> wrote:

> On Tue, Mar 09, 2010 at 08:42:44PM +0100, Sebastian Hungerecker wrote:
> > On 09.03.2010 20:04, boblettoj wrote:
> >> score :: String ->  String ->  String
> >> score [s] [] = false
> >> score [s] [g] =
> >>      if valid 4 g
> >>      then (s1 ++ s2 ++ s3 ++ s4) where
> >>              s1 = "Golds "
> >>              s2 = show (gold s g)
> >>              s3 = ", Silvers "
> >>              s4 = show (silver s g)
> >>      else "Bad Guess"
> >>
> >
> > Apart from the parse error there is also a type error
> > in your code:
> > When the second argument is empty, you return false
> > although you declared the function to return a String,
> > not a boolean.
>
> Not quite; data Bool = True | False, and the code uses a lowercase 'f'
> 'false'. Perhaps 'false' is defined as a String somewhere else?  A bit
> odd, perhaps, but not necessarily a type error.
>
> -Brent
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