gistfile1.hs

slice :: (Slice sh, Shape sh, Elt a) => Int -> Int -> Array (sh :. Int) a -> Array (sh :. Int) a
slice from to array = 
         fromFunction (z :. (to - from + 1)) (\(z :. ix) -> array ! (z :. (ix + from)))
    where (z :. _) = extent array

cumsum :: 
    (FullShape uf ~ uf,
    Slice uf,
    Slice (SliceShape uf),
    Shape uf,
    Shape (SliceShape uf),
    Elt a,
    Num a) =>
    Array (uf :. Int) a -> Array (uf :. Int) a
cumsum array = traverse array id $ cumsum' array
    where 
        cumsum' array f (sh :. outer) = 
            Repa.sumAll $ 
            Surf.slice 0 outer $ 
            Repa.slice array (sh :. All)