On Thursday 02 September 2010 19:29:23, Alec Benzer wrote:
I came up with this (dealing with non-multiple of 8 numbers of bits)
bitsToBytes :: [Bool] -> [Word8] bitsToBytes [] = [] bitsToBytes bits = map bitsToByte (getChunks bits) where bitsToByte = foldl' (\byte bit -> byte*2 + if bit then 1 else 0) 0
getChunks :: [Bool] -> [[Bool]] getChunks [] = [] getChunks xs | length xs < 8 = getChunks $ take 8 (xs ++ repeat False)
Pet peeve. Don't use `length xs < k' (or <=, ==, >=, >). That fails hard on infinite lists, also it is slow and prone to cause a space leak on long lists. Remember, length must walk the entire list. Instead of length xs < k use null (drop (k-1) xs), other combinations of not, null and drop for the other tests. Or you can use lazy Peano numbers and check genericLength xs < (8 :: Peano).
| otherwise = let (these,rest) = splitAt 8 xs in these:getChunks rest