Hello victor I decided to use your solution, since I find it more elegant than mine :)) data Chunk n a = Chunk !a !n !n deriving instance (Show n, Show a) => Show (Chunk n a) cweight :: Num n => Chunk n a -> n cweight (Chunk _ l h) = h - l csplit :: Num n => Chunk n a -> n -> (Chunk n a, Chunk n a) csplit (Chunk a l h) n = ( (Chunk a l (l + n)), (Chunk a (l+n) h) ) chunk :: (Num n, Ord n) => n -> [Chunk n a] -> [[Chunk n a]] chunk target = go target target where go _ _ [] = [] go tgt gap [x] = golast tgt gap x go tgt gap ~(x:xs) = let gap' = gap - cweight x in if | gap' > 0 -> cons1 x $ go tgt gap' xs | gap' == 0 -> [x] : go tgt tgt xs | (x1, x2) <- csplit x gap -> [x1] : go tgt tgt (x2 : xs) cons1 !x ~(c:cs) = (x : c) : cs golast tgt gap x = if | cweight x <= gap -> [x] : [] | (x1, x2) <- csplit x gap -> [x1] : golast tgt tgt x2 {-# SPECIALIZE chunk :: Int -> [Chunk Int FilePath] -> [[Chunk Int FilePath]] #-} But when compiling I have these warning
src/Hkl/Projects/Sixs.hs:(59,5)-(65,69): warning: [-Wincomplete-uni-patterns] Pattern match(es) are non-exhaustive In a pattern binding: Patterns not matched: [] | 59 | go _ _ [] = [] | ^^^^^^^^^^^^^^^^^^^^^^^...
I do not understand this one
src/Hkl/Projects/Sixs.hs:67:5-35: warning: [-Wincomplete-uni-patterns] Pattern match(es) are non-exhaustive In a pattern binding: Patterns not matched: [] | 67 | cons1 !x ~(c:cs) = (x : c) : cs | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If this is something which can not be reach, is it possible to explain to ghc how to avoid these warning ? cheers Fred