Am Samstag, 21. Februar 2009 23:29 schrieb Thomas Davie:
How about this:
maxTableColumnWidths :: [[String]] -> [Int] maxTableColumnWidths = map (maximum . map length)
That's not what he needs, maxTableColumnWidths = map (maximum . map length) . transpose would be it. But I'm afraid that wouldn't solve his memory problems. Regarding the memory problems: String is rather a memory hog anyway. Keith, have you considered using ByteStrings? That might solve your memory problems with a straightforward algorithm. Also, if the rows can contain many columns, it is wasteful to calculate the length of prevMaxValues for every row. You could either have that as a parameter, or use a custom zipWith: zipWithD :: (a -> a -> a) -> [a] -> [a] -> [a] zipWithD f (x:xt) (y:yt) = f x y:zipWithD f xt yt zipWithD _ [] ys = ys zipWithD _ xs [] = xs Then maxRowFieldWidths would become maxRowFieldWidths row prev = zipWithD max (map length row) prev or, pointfree: maxRowFieldWidths = zipWithD max . map length seqList can also be written as seqList = foldr seq False That would make maxTableColumnWidths = foldr ((seqList .) . zipWithD max) [] I'm not sure if that is strict enough, though. Also, you might try maxTCWs = foldr seq [] . foldr (zipWithD max) [] , but I expect that to be a bad memory citizen.
Bob
Cheers, Daniel