Data.List.sortFun
I've found these two functions useful often enough to suggest adding it to Data.List:
{-# RULES
"sortFun/fst" forall . sortFun fst = sortFun' fst
"sortFun/snd" forall . sortFun snd = sortFun' snd
#-}
sortFun :: Ord b => (a -> b) -> [a] -> [a]
sortFun f = map snd . sortFun' fst . map (\x -> (f x, x))
sortFun' :: Ord b => (a -> b) -> [a] -> [a]
sortFun' f = Data.List.sortBy (\x y -> compare (f x) (f y))
I am not terribly fond of the name "sortFun". If anybody has a better suggestion...
Trac metadata
Trac field | Value |
---|---|
Version | 6.8.3 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | libraries/base |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | Unknown |
Architecture | Unknown |