Look also at safe package <http://hackage.haskell.org/package/safe> 2012/3/13 Chris Wong <chrisyco+haskell-cafe@gmail.com>
On Tue, Mar 13, 2012 at 12:24 PM, Chris Smith <cdsmith@gmail.com> wrote:
On Mon, Mar 12, 2012 at 3:14 PM, Kevin Clees <k.clees@web.de> wrote:
Now my function looks like this:
tmp:: [(Int, Int)] -> Int -> (Int, Int) tmp [] y = (0,0) tmp xs y = xs !! (y-1)
Just a warning that this will still crash if the list is non-empty by the index exceeds the length. That's because your function is no longer recursive, so you only catch the case where the top-level list is empty. The drop function doesn't crash when dropping too many elements though, so you can do this and get a non-recursive function that's still total:
tmp :: [(Int,Int)] -> Int -> (Int, Int) tmp xs y = case drop (y-1) xs of [] -> (0,0) Just (x:_) -> x
That last line should be
(x:_) -> x
without the "Just". Hopefully that'll save a bit of confusion.
Chris
-- Chris Smith
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