Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

added 'Relude.List.permutations' #397

Open
wants to merge 1 commit into
base: main
Choose a base branch
from
Open

added 'Relude.List.permutations' #397

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
27 changes: 26 additions & 1 deletion src/Relude/List.hs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -20,16 +20,18 @@ module Relude.List
, (!!?)
, maybeAt
, partitionWith
, permutations
) where


import Relude.Base ((<))
import Relude.Bool (otherwise)
import Relude.Function (flip, (.))
import Relude.Function (flip, (.), id)
import Relude.List.NonEmpty
import Relude.List.Reexport
import Relude.Monad (Either, Maybe (..), partitionEithers)
import Relude.Numeric (Int, (-))
import Relude.Foldable (foldr)


-- $setup
Expand Down Expand Up @@ -108,6 +110,29 @@ partitionWith :: (a -> Either b c) -> [a] -> ([b], [c])
partitionWith f = partitionEithers . map f
{-# INLINE partitionWith #-}

{- | The 'permutations' function returns the list of all permutations of the argument.
Unlike its Prelude implementation, thiv version returns NonEmpty.

>>> permutations "abc"
"abc" :| ["bac","cba","bca","cab","acb"]

>>> permutations []
[] :| []

@since 1.1.0.0
-}
permutations :: [a] -> NonEmpty [a]
permutations xs0 = xs0 :| perms xs0 []
where
perms [] _ = []
perms (t:ts) is = foldr interleave (perms ts (t:is)) (permutations is)
where interleave xs r = let (_,zs) = interleave' id xs r in zs
interleave' _ [] r = (ts, r)
interleave' f (y:ys) r = let (us,zs) = interleave' (f . (y:)) ys r
in (y:us, f (t:y:us) : zs)
{-# INLINE permutations #-}


{- $reexport
Most of the "Data.List" types and function.

Expand Down
2 changes: 1 addition & 1 deletion src/Relude/List/Reexport.hs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ module Relude.List.Reexport

import Data.List (break, drop, dropWhile, filter, genericDrop, genericLength, genericReplicate,
genericSplitAt, genericTake, group, inits, intercalate, intersperse, isPrefixOf,
iterate, map, permutations, repeat, replicate, reverse, scanl, scanl', scanl1,
iterate, map, repeat, replicate, reverse, scanl, scanl', scanl1,
scanr, scanr1, sort, sortBy, sortOn, span, splitAt, subsequences, tails, take,
takeWhile, transpose, uncons, unfoldr, unzip, unzip3, zip, zip3, zipWith, (++))
import GHC.Exts (sortWith)
Expand Down