Thanks folks. Francesco Cool - I just came to that conclusion too and did tupleOrder :: (Char, Int) -> (Char, Int) -> Ordering tupleOrder (c1, x1) (c2, x2) -- char compared by ord and a is less than b! | x1 == x2 && c1 <= c2 = GT | x1 == x2 && c1 >= c2 = LT | x1 < x2 = LT | x1 > x2 = GT and then did sortBy. Erlend I’ll try that - Monoids have such an understated elegance. :)

On 13 Dec 2016, at 16:01, Erlend Hamberg wrote:

There is a really nice solution that takes advantage of Ordering's Monoid instance (see https://wiki.haskell.org/Monoid https://wiki.haskell.org/Monoid).

The imports you need:

import Data.List (sortBy) import Data.Ord (Down(..), comparing) import Data.Monoid ((<>)) -- the “mappend” operator

You can then combine two calls to `comparing`

sortBy (comparing (Down . snd) <> comparing fst) xs

(`Down` is just a newtype that reverses the ordering, since you wanted the first element in descending order and the second in ascending order.)

On Tue, 13 Dec 2016 at 16:30 Francesco Ariis mailto:fa-ml@ariis.it> wrote: On Tue, Dec 13, 2016 at 02:36:39PM +0000, mike h wrote:

...

Hi,

I’m trying to sort a list of tuples. A char and a count of that char (Char , Int) e.g.

[ ('r',2), ('c',2),('a', 2), ('b',3), ('f',2)]

e.g. ‘r’ occurs twice etc. The order should be based on the count first and then ties broken by the natural ordering of char.

You should provide sortBy with an appropriate compare function, e.g.

comp (a,b) (c,d) | a > c = GT | -- etc etc.

or go with the manky but working hack:

λ> :m Data.List λ> sortOn (\(a, b) -> b*(-100) + fromEnum a) [('r',2), ('c',2),('a', 2), ('b',3), ('f',2)] [('b',3),('a',2),('c',2),('f',2),('r',2)]

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