Added Eq1, Ord1, Read1 and Show1 instances for NonEmpty

Reviewers: austin, hvr, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2755

2 files changed, 25 insertions, 0 deletions

diff --git a/libraries/base/Data/List/NonEmpty.hs b/libraries/base/Data/List/NonEmpty.hs
index 1cba3e5301..b4da532b1d 100644
--- a/libraries/base/Data/List/NonEmpty.hs
+++ b/libraries/base/Data/List/NonEmpty.hs
@@ -109,7 +109,9 @@ import           Data.Data           (Data)
 import           Data.Foldable       hiding (length, toList)
 import qualified Data.Foldable       as Foldable
 import           Data.Function       (on)
+import           Data.Functor.Classes (Eq1(..), Ord1(..), Read1(..), Show1(..))
 import qualified Data.List           as List
+import           Data.Monoid         ((<>))
 import           Data.Ord            (comparing)
 import qualified GHC.Exts            as Exts (IsList(..))
 import           GHC.Generics        (Generic, Generic1)
@@ -122,6 +124,27 @@ infixr 5 :|, <|
 data NonEmpty a = a :| [a]
   deriving ( Eq, Ord, Show, Read, Data, Generic, Generic1 )
 
+-- | @since 4.10.0.0
+instance Eq1 NonEmpty where
+  liftEq eq (a :| as) (b :| bs) = eq a b && liftEq eq as bs
+
+-- | @since 4.10.0.0
+instance Ord1 NonEmpty where
+  liftCompare cmp (a :| as) (b :| bs) = cmp a b <> liftCompare cmp as bs
+
+-- | @since 4.10.0.0
+instance Read1 NonEmpty where
+  liftReadsPrec rdP rdL p s = readParen (p > 5) (\s' -> do
+    (a, s'') <- rdP 6 s'
+    (":|", s''') <- lex s''
+    (as, s'''') <- rdL s'''
+    return (a :| as, s'''')) s
+
+-- | @since 4.10.0.0
+instance Show1 NonEmpty where
+  liftShowsPrec shwP shwL p (a :| as) = showParen (p > 5) $
+    shwP 6 a . showString " :| " . shwL as
+
 -- | @since 4.9.0.0
 instance Exts.IsList (NonEmpty a) where
   type Item (NonEmpty a) = a
diff --git a/libraries/base/changelog.md b/libraries/base/changelog.md
index dcc171979f..5983747a96 100644
--- a/libraries/base/changelog.md
+++ b/libraries/base/changelog.md
@@ -28,6 +28,8 @@
 
   * Add `Data` instance for `Const` (#12438)
 
+  * Added `Eq1`, `Ord1`, `Read1` and `Show1` instances for `NonEmpty`.
+
 ## 4.9.0.0  *May 2016*
 
   * Bundled with GHC 8.0