Re: [Haskell-cafe] Why this cannot be compiled?

Hum.... I must lost my mind.... Thank you. On Mon, Jul 13, 2009 at 3:33 PM, Ketil Malde wrote:

Magicloud Magiclouds 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

-- 竹密岂妨流水过 山高哪阻野云飞