{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE Safe              #-}

module List
       ( ordNub
       , sortOn
       , list
       , unzip
       , unzip3
       , zip
       , zip3
       ) where

import           Data.Function ((.))
import           Data.Functor  (fmap)
import           Data.List     (sortBy, unzip, unzip3, zip, zip3)
import           Data.Ord      (Ord, comparing)
import qualified Data.Set      as Set

sortOn :: (Ord o) => (a -> o) -> [a] -> [a]
sortOn = sortBy . comparing

-- O(n * log n)
ordNub :: (Ord a) => [a] -> [a]
ordNub l = go Set.empty l
  where
    go _ []     = []
    go s (x:xs) =
      if x `Set.member` s
      then go s xs
      else x : go (Set.insert x s) xs

list :: [b] -> (a -> b) -> [a] -> [b]
list def f xs = case xs of
  [] -> def
  _  -> fmap f xs