I tried this version,
however....
nsortBy cmp l = mergesort compare l should be:
nsortBy cmp l = mergesort cmp l
Thanks Sorry, with this version I meant:
nsort l = mergesort compare l nsortBy cmp l = mergesort compare l
mergesort :: (a -> a -> Ordering) -> [a] -> [a] mergesort cmp = mergesort' cmp . map wrap
mergesort' :: (a -> a -> Ordering) -> [[a]] -> [a] mergesort' cmp [] = [] mergesort' cmp [xs] = xs mergesort' cmp xss = mergesort' cmp (merge_pairs cmp xss)
merge_pairs :: (a -> a -> Ordering) -> [[a]] -> [[a]] merge_pairs cmp [] = [] merge_pairs cmp [xs] = [xs] merge_pairs cmp (xs:ys:xss) = merge cmp xs ys : merge_pairs cmp xss
merge :: (a -> a -> Ordering) -> [a] -> [a] -> [a] merge cmp xs [] = xs merge cmp [] ys = ys merge cmp (x:xs) (y:ys) = case x `cmp` y of GT -> y : merge cmp (x:xs) ys LT -> x : merge cmp xs (y:ys) EQ -> x : merge cmp xs ys
wrap :: a -> [a] wrap x = [x]