```{-# LANGUAGE NoImplicitPrelude, UnicodeSyntax #-}

{-|
Module     : Data.List.Unicode
Copyright  : 2009–2011 Roel van Dijk
Maintainer : Roel van Dijk <vandijk.roel@gmail.com>
-}

module Data.List.Unicode
( (⧺)
, (∈), (∋), (∉), (∌)
, (∪), (∖), (∆), (∩)
) where

-------------------------------------------------------------------------------
-- Imports
-------------------------------------------------------------------------------

-- from base:
import Data.Bool     ( Bool )
import Data.Eq       ( Eq )
import Data.Function ( flip )
import Data.List     ( (++), elem, notElem, union, (\\), intersect )

-------------------------------------------------------------------------------
-- Fixities
-------------------------------------------------------------------------------

infix  4 ∈
infix  4 ∋
infix  4 ∉
infix  4 ∌
infixr 5 ⧺
infixl 6 ∪
infixr 6 ∩
infixl 9 ∖
infixl 9 ∆

-------------------------------------------------------------------------------
-- Symbols
-------------------------------------------------------------------------------

{-|
(&#x29FA;) = ('++')

U+29FA, DOUBLE PLUS
-}
(⧺) ∷ [α] → [α] → [α]
(⧺) = (++)

{-|
(&#x2208;) = 'elem'

U+2208, ELEMENT OF
-}
(∈) ∷ Eq α ⇒ α → [α] → Bool
(∈) = elem

{-|
(&#x220B;) = 'flip' (&#x2208;)

U+220B, CONTAINS AS MEMBER
-}
(∋) ∷ Eq α ⇒ [α] → α → Bool
(∋) = flip (∈)

{-|
(&#x2209;) = 'notElem'

U+2209, NOT AN ELEMENT OF
-}
(∉) ∷ Eq α ⇒ α → [α] → Bool
(∉) = notElem

{-|
(&#x220C;) = 'flip' (&#x2209;)

U+220C, DOES NOT CONTAIN AS MEMBER
-}
(∌) ∷ Eq α ⇒ [α] → α → Bool
(∌) = flip (∉)

{-|
(&#x222A;) = 'union'

U+222A, UNION
-}
(∪) ∷ Eq α ⇒ [α] → [α] → [α]
(∪) = union

{-|
(&#x2216;) = ('\\')

U+2216, SET MINUS
-}
(∖) ∷ Eq α ⇒ [α] → [α] → [α]
(∖) = (\\)

{-|
Symmetric difference

a &#x2206; b = (a &#x2216; b) &#x222A; (b &#x2216; a)

U+2206, INCREMENT
-}
(∆) ∷ Eq α ⇒ [α] → [α] → [α]
a ∆ b = (a ∖ b) ∪ (b ∖ a)

{-|
(&#x2229;) = 'intersect'

U+2229, INTERSECTION
-}
(∩) ∷ Eq α ⇒ [α] → [α] → [α]
(∩) = intersect
```