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instance Read

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tenho como trabalho realizar uma instance show e read relativamente a manipulaçao de tipos.

como objectivo no show tenho que passar, por exemplo show (BF [Read, While (BF [Print, DecVal])]) vai ser igual a string ",[.-]", e read ",[.-]" vai ter como resultado BF [Read, While (BF [Print, DecVal])]

de codigo realizado (acho eu que correcto) tenho:

data BF=BF [bFCommand]
               -- deriving (Eq,Show)
data BFCommand =IncPtr  |DecPtr |IncVal |DecVal |Read |Print |While BF

instance Show BF where
    show (BF is)=concatMap show is

instance Show BFCommand where
        show IncPtr =  ">"
        show DecPtr =  "<"
        show IncVal =  "+"
        show DecVal =  "-"
        show Read   =  ","
        show Print  =  "."
        show (While s) = "["++show s++"]"

este realiza o pretendido, a minha duvida esta toda no read:

instance Read BF where
      readsPrec _ = readBF

agradecia que alguem me desse ajudas relativamente a completar a parte do read, pois nao sei como defenir o readBF.

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