The code by Twan can be reduced to this:
diagN = concat . foldr f [[[]]]
f :: [a] -> [[[a]]] -> [[[a]]]
f xs ys = foldr (g ys) [] xs
g :: [[[a]]] -> a -> [[[a]]] -> [[[a]]]
g ys x xs = merge (map (map (x:)) ys) ([] : xs)
merge :: [[a]] -> [[a]] -> [[a]]
merge [] ys = ys
merge xs [] = xs
merge (x:xs) (y:ys) = (x++y) : merge xs ys
But my feeling is that this can still be simplified further. Or at
least refactored so it is clear what actually is going on!
--
Sjoerd Visscher
sjo...@w3future.com
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