Proposal: add an order-reversing newtype to Data.Ord

Andreas Abel andreas.abel at
Wed Jul 11 08:11:13 CEST 2012

On 11.07.12 4:31 AM, Conrad Parker wrote:
> On 10 July 2012 23:28, Twan van Laarhoven<twanvl at>  wrote:
>> On 10/07/12 14:31, Strake wrote:
>>> On 09/07/2012, Edward Kmett<ekmett at>  wrote:
>>>> I would be happy enough with just re-exporting Down and calling it a day.
>>>> Last time this topic came up it was bikeshedded to death without
>>>> resolution.
>>> Why is it called "Down"? Is this a mathematical term?
>> I believe the Down newtype was introduced for use with extended list
>> comprehension, things like
>>      [ name u | u<- users, then sort (Down (salary x)) ].
> That is illustrative; it reads much better than Reverse or DualOrd
> would, and I expect that sort is the most common use of an Ord
> instance.
> +1 for re-exporting Down.

+1 for Down.   (DualOrd would be also ok, but sounds artifical.  Reverse 
has too much connotation of list-reverse for my taste.)

Andreas Abel  <><      Du bist der geliebte Mensch.

Theoretical Computer Science, University of Munich
Oettingenstr. 67, D-80538 Munich, GERMANY

andreas.abel at

More information about the Libraries mailing list