On Sun, 2008-10-05 at 17:39 +0200, Twan van Laarhoven wrote:
Hello list,
Almost all uses of sortBy in user code use 'comparing', 'on' or a similar construction [1]. I think we should add a function that makes this common behavior more convenient:
sortOn :: Ord b => (a -> b) -> [a] -> [a]
I think fewer names and more combinations is usually best unless there is a really compelling reason. Just because things are often used in combination doesn't mean we have to make a new name to represent that composition. As functional programmers we are very used to using composition, especially simple function application. What is wrong with sortBy (comparing fieldFoo) ? It's not very long, it's pretty descriptive and easily generalises using the 'on' function. The only thing missing here is equating. I still have to define that myself to write: groupBy (equating fieldBar) I know I can write groupBy ((==) `on` fieldBar) but that just does not read so nicely. So perhaps I should file a counter-proposal suggesting that all we need to do is to add equating to Data.Eq. :-) Duncan