[Haskell-cafe] Read Instance code.

[Ivan Lazar Miljenovic]

Andy Stewart <lazycat.manatee at gmail.com> writes:

> Hi all,
>
> I have some incorrect "Read instance" make i got error "Prelude.read: no
> parse", and i don't know how to fix it. 
>
>
> newtype SerializedWindow = SerializedWindow (Maybe DrawWindow)
>     
> instance Show SerializedWindow where    
>   show _ = "SerializedWindow Nothing"
>            
> instance Read SerializedWindow where           
>     readsPrec _ str = [(SerializedWindow Nothing, idStr) 
>                            | (val :: String, idStr) <- reads str]

Try using Derive or DrIFT to generate a proto-typical instance for you,
and then hack that and make it neater.  If you don't care about
cross-compiler compatability, using ReadP rather than ReadS also results
in nicer parsing code.

-- 
Ivan Lazar Miljenovic
Ivan.Miljenovic at gmail.com
IvanMiljenovic.wordpress.com