[Haskell-cafe] Clausula where

[vieira.ufpi at gmail.com]

I’m using GHCi in a Haskell  version 7.10.2 and using this fragmente of coding:


data ArvBinA t = Folha t | No Int (ArvBinA t) (ArvBinA t) deriving (Eq, Ord, Show)


arvbina = No 4 (No 2 (Folha 14) (Folha 09)) (No 2 (Folha 19) (Folha 51))


tamArvBinA :: ArvBinA t -> Int
tamArvBinA (Folha x) = 1
tamArvBinA (No n xt yt) = n


rotula :: ArvBinA t -> ArvBinA t -> ArvBinA t
rotula ae ad
   = No n ae ad where n = (tamArvBinA ae) + (tamArvBinA ad)


listoArvBinA ::  (Eq t) => [t] -> ArvBinA t
listoArvBinA xs
   |m == 0    = Folha (head xs)
   |otherwise = rotula (listoArvBinA xse) (listoArvBinA xsd)
                          where  m              =  (length xs) `div` 2 
                                       (xse, xsd)  =  (take m xs,  drop m xs) 


After compiling there is this message: 


parse error on input   ‘=’. 


There is someone that he/she can help me? I think that’is na error by clause where and the offside rule, or so, but I’m not right of this.


Thanks in advance for some help

Francisco Vieira






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