I expect you'll get many replies...
row (Grid s l) n = if (n >= s) then [] else l !! n
col g@(Grid s l) n = if (n >= s) then [] else col_ g n 0 where col_ (Grid s l) n i = if (i >= s) then [] else (head l !! n) : col_ (Grid s (tail l)) n (i + 1)
While such low-level approach (focus on the element) can certainly be made to work, but Haskell encourages you to think in higher level constructs. I haven't seen this problem before but I would map the original array from [[Int]] -> [(Int, (Int, Int), Int, Int)], that is: a list of tuples consisting of the original element, its coordinate, the row maximum and the column minimum. From there its a trivial filter to find your results. (I'm sure there's a more elegant solution).
My question: With the way Haskell works (thunks, lazy evaluation, and all that mystery), is it actually worth the trouble of /precalculating/ the maximum row values and minimum column values, to compare cell values against? Or will, for example, something like (smallest_list_value (col array 1)) definitely only evaluate once?
There's not enough context to answer the specific question, but lazy evaluation isn't magic and the answer is probably "no". Tommy