sortOn package:sort

sortOn :: Ord b => (a -> b) -> [a] -> [a]

Sort a list by comparing the results of a key function applied to each element. sortOn f is equivalent to sortBy (comparing f), but has the performance advantage of only evaluating f once for each element in the input list. This is called the decorate-sort-undecorate paradigm, or Schwartzian transform.

groupSortOn :: Ord k => (a -> k) -> (k -> a -> [a] -> b) -> [a] -> [b]

sort Data.Sort

Sort a list of elements with a stable sort, using the argument compare function determine the ordering, grouping together the equal elements with the grouping function

monoidSortOn :: (Monoid a, Ord k) => (a -> k) -> [a] -> [a]

sort Data.Sort

Sort the list, agregating duplicates with the monoid and ordering the elements by the items generated by the argument function.

uniqueSortOn :: Ord k => (a -> k) -> [a] -> [a]

sort Data.Sort

Sort the list, discarding duplicates and ordering the elements by the items generated by the argument function.