[Haskell-beginners] How to get each list in a list of lists for filter

[Harald Bögeholz]

Am 31.12.13 19:48, schrieb Angus Comber:
> I am getting a list of lists from chop9.  I want to somehow filter each
> element in the list.  How do I do that.
> 
> I have encoded binary data eg [1,1,0,0,1,0] etc
> 
> Each 9th bit is a parity bit which is checked using this function:
> 
> type Bit = Int
> 
> paritychecker :: [Bit] -> Bool
> paritychecker xs | length xs == 9 && ((sum (init xs)) `mod` 2) == (last xs)
> = True
>                  | otherwise = False
> 
> 
> In the stream (the list) I use chop to retrieve each block of 9 bits as in:
> 
> chop9 :: [Bit] -> [[Bit]]
> chop9 [] = []
> chop9 bits = take 8 bits : chop9 (drop 8 bits)
> 
> I have been playing with this sort of thing:
> filter paritychecker ??? chop9 [1,0,0,0,1,1,1,0,0,...]
> 
> But doesn't work.

Could a simple typo be the problem?

Shouldn't chop9 .. take 9 bits ... and ... drop 9 bits ... instead of 8?

Harald
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