#2406: Data.List.sortFun
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Reporter: lpsmith | Owner:
Type: feature request | Status: new
Priority: normal | Component: libraries/base
Version: 6.8.3 | Severity: normal
Keywords: | Testcase:
Architecture: Unknown | Os: Unknown
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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...
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2406>
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