[Haskell-cafe] is there already a function that does this?
lennart at augustsson.net
Sat Mar 3 16:48:17 EST 2007
Those both look roughly like what I would do.
On Mar 3, 2007, at 21:35 , Jared Jennings wrote:
> -- Sort the [a]'s by the [b]'s.
> sortByKeys :: (Ord b) => [b] -> [a] -> [a]
> sortByKeys keys values = map snd $ sortBy compareFst (zip keys values)
> where compareFst x y = compare (fst x) (fst y)
> -- Sort a list by an IO-returning compare function.
> sortByM :: (Monad m, Ord b) => (a -> m b) -> [a] -> m [a]
> sortByM fun lis = mapM fun lis >>= \keys -> return $ sortByKeys
> keys lis
> Is there a function that can make sortByM out of sortByKeys? I don't
> know of one, but having been writing haskell for a few weeks, it sort
> of smells to me like there probably is one.
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