Proposal #2659: Add sortOn and friends to Data.List

[apfelmus]

Duncan Coutts wrote:
>> +1 concerning Down,
>>
>> but I don't like the name. In particular I don't like the "get" prefix
>> in "getDown". I'd simply use
> 
> Can't we do it with just some compare flip function:
> 
> sortBy (thing compare)
> 
> or
> 
> sortBy (thing $ comparing fieldFoo)
> 
> Would that work and what would be a good name?

thing = flip  works :)

But  Down  could be useful on its own, for instance for converting
a heap that stores elements in maximum order into one that stores them
in minimum order, i.e. when there is an Ord class constraint instead of
a simple higher-order function. Some exploration of the design space here

  http://thread.gmane.org/gmane.comp.lang.haskell.cafe/35988

Hm, I think that the  Cache b a  thing is more general, though, it may
be worth extending this to a full proposal.


Regards,
apfelmus