diff options
| author | iori tsu <matsuhara.iori@scrive.com> | 2021-04-25 08:58:15 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-04-27 00:00:08 -0400 |
| commit | d9ceb2fb51b037a330a6cfaf129c24ea7f1ac644 (patch) | |
| tree | 6b79ed23abfb1694172aaeab6e3793ac8a242633 | |
| parent | c1549069c15117b06c521bd3de966754f3fc62ec (diff) | |
| download | haskell-d9ceb2fb51b037a330a6cfaf129c24ea7f1ac644.tar.gz | |
Add documentation for GHC.Exts.sortWith
sortWith has the same type definition as `Data.List.sortOn` (eg: `Ord b => (a -> b) -> [a] -> [a]`).
Nonetheless, they behave differently, sortOn being more efficient.
This merge request add documentation to reflect on this differences
| -rwxr-xr-x | libraries/base/GHC/Exts.hs | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/libraries/base/GHC/Exts.hs b/libraries/base/GHC/Exts.hs index 0e3cd14407..d0a32b03d1 100755 --- a/libraries/base/GHC/Exts.hs +++ b/libraries/base/GHC/Exts.hs @@ -149,6 +149,11 @@ the [] = errorWithoutStackTrace "GHC.Exts.the: empty list" -- | The 'sortWith' function sorts a list of elements using the -- user supplied function to project something out of each element +-- +-- In general if the user supplied function is expensive to compute then +-- you should probably be using 'Data.List.sortOn', as it only needs +-- to compute it once for each element. 'sortWith', on the other hand +-- must compute the mapping function for every comparison that it performs. sortWith :: Ord b => (a -> b) -> [a] -> [a] sortWith f = sortBy (\x y -> compare (f x) (f y)) |