[Haskell-cafe] Why this cannot be compiled?

[Magicloud Magiclouds]

Hum.... I must lost my mind....
Thank you.

On Mon, Jul 13, 2009 at 3:33 PM, Ketil Malde<ketil at malde.org> wrote:
> Magicloud Magiclouds <magicloud.magiclouds at gmail.com> writes:
>
>>  43 instance Read Attribute where
>>  44   readsPrec _ str = [ (mkAttr attr_ color, rest) | (attr_, rest1) <- lex str
>>  45                                                  , (color, rest)  <- case reads rest1 of
>>  46                                                        [(color_, rest_)] -> (color_, rest_)
>>  47                                                        _ -> (Color 0 0 0, rest1) ]
>
> Doesn't the (color,rest) pair in the list comprehension need to be
> pulled from a list?  The case expression only returns a pair so you're
> basically left with [something| something, (color,rest) <- (somecolor,somerest) ]
>
> Since you're only producing a single (color,rest) for each rest1, you might
> consider lifting it out in the left side of the list comprehension.
>
> -k
> --
> If I haven't seen further, it is by standing in the footprints of giants
>



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