-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On Tue, Jul 14, 2009 at 1:49 AM, Magicloud Magiclouds wrote:

Hi, I have a data structure, which shows like this: AttrBgColor {bgColor = Color 0 0 0} And the following is my Read code. But it failed parsing.... 31 instance Read Attribute where 32 readsPrec _ str = [ (mkAttr attr_ color, rest) | (attr_, rest1) 33 , (color, rest) 34 || (isPrefixOf " {fgColor = " rest1) 35 then case reads $ drop 12 rest1 of 36 [(color_, rest_)] -> [(color_, rest_)] 37 _ -> [(Color 0 0 0, rest1)] 38 else [(Color 0 0 0, rest1)] ] 39 where mkAttr "AttrFgColor" color = AttrFgColor color 40 mkAttr "AttrBgColor" color = AttrBgColor color 41 mkAttr "AttrInverse" _ = AttrInverse 42 mkAttr "AttrWeak" _ = AttrWeak 43 mkAttr "AttrUnderline" _ = AttrUnderline

Perhaps I am mis-understanding you, but why aren't you just deriving Read & Show? eg. data AttrBgColor = AttrBgColor { bgColor :: Color Int Int Int } deriving (Read, Show) It would certainly seem to be much easier and more reliable than hand-rolling an ad hoc parser. - -- gwern -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEAREKAAYFAkpdJS8ACgkQvpDo5Pfl1oI/1QCfUgfHVsD/PMmgS6Z1sMMPljWt zOkAn0hQ3GBLFxHCO6ryoYyvPZ+nDJdp =qR5d -----END PGP SIGNATURE-----