Sorting tuples in haskell lists

Question

I'd like to sort a list of tuples by the third or fourth element (say c or d) in the list of type:

myList = [(a,b,c,d,e)]

I know if the tuple is of type (a,b) I can use the following approach:

mySort xmyList = sortBy (compare `on` snd) x

But the type of sortBy will not work on tuples with length greater than two (so obviously there is no point writing an accessor function for thd or fth ) :

(a -> a -> Ordering) -> [a] -> [a]

Answer 1

But the type of sortBy will not work on tuples with length greater than two

No, it actually works for any list. For instance, if you want to sort on c , just do:

mySort xmyList = sortBy (compare `on` (\(a,b,c,d,e) -> c)) x

or

mySort xmyList = sortBy (comparing thirdOf5) x
   where thirdOf5 (_,_,c,_,_) = c