From a23fcf204e3ceaf2f21092b8efc4b43e0f33659c Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@github.com>
Date: Mon, 14 Mar 2016 18:30:44 -0400
Subject: [PATCH] Add an Alternative instance over Adjoined.

---
 src/Data/Adjoined.hs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/Data/Adjoined.hs b/src/Data/Adjoined.hs
index 4bc955acf..6a7c81d23 100644
--- a/src/Data/Adjoined.hs
+++ b/src/Data/Adjoined.hs
@@ -1,6 +1,7 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 module Data.Adjoined where
 
+import Control.Applicative
 import Control.Monad
 import Data.Align
 import Data.Bifunctor.These
@@ -38,6 +39,10 @@ instance Applicative Adjoined where
   pure = return
   (<*>) = ap
 
+instance Alternative Adjoined where
+  empty = Adjoined mempty
+  Adjoined a <|> Adjoined b = Adjoined (a >< b)
+
 instance Monad Adjoined where
   return = Adjoined . return
   Adjoined a >>= f = case viewl a of