Add Eq1, Show1, Read1 Complex instances

2 files changed, 23 insertions, 0 deletions

diff --git a/libraries/base/Data/Functor/Classes.hs b/libraries/base/Data/Functor/Classes.hs
index e719c8ffe8..80b662372c 100644
--- a/libraries/base/Data/Functor/Classes.hs
+++ b/libraries/base/Data/Functor/Classes.hs
@@ -70,6 +70,7 @@ import Data.Functor.Identity (Identity(Identity))
 import Data.Proxy (Proxy(Proxy))
 import Data.List.NonEmpty (NonEmpty(..))
 import Data.Ord (Down(Down))
+import Data.Complex (Complex((:+)))
 
 import GHC.Read (expectP, list, paren)
 
@@ -661,6 +662,25 @@ instance Read1 Down where
 instance Show1 Down where
     liftShowsPrec sp _ d (Down x) = showsUnaryWith sp "Down" d x
 
+-- | @since 4.16.0.0
+instance Eq1 Complex where
+    liftEq eq (x :+ y) (u :+ v) = eq x u && eq y v
+
+-- | @since 4.16.0.0
+instance Read1 Complex where
+    liftReadPrec rp _  = parens $ prec 9 $ do
+        x <- step rp
+        expectP (Symbol ":+")
+        y <- step rp
+        return (x :+ y)
+
+    liftReadListPrec = liftReadListPrecDefault
+    liftReadList     = liftReadListDefault
+
+-- | @since 4.16.0.0
+instance Show1 Complex where
+    liftShowsPrec sp _ d (x :+ y) = showParen (d >= 10) $
+        sp 10 x . showString " :+ " . sp 10 y
 
 -- Building blocks
 
diff --git a/libraries/base/changelog.md b/libraries/base/changelog.md
index 9c25b92b4c..71649ad175 100644
--- a/libraries/base/changelog.md
+++ b/libraries/base/changelog.md
@@ -11,6 +11,9 @@
   * Add `Semigroup` and `Monoid` instances for `Data.Functor.Product` and
     `Data.Functor.Compose`.
 
+  * Add `Eq1`, `Read1` and `Show1` instance for `Complex`;
+    add `Eq1`, `Ord1`, `Show1` and `Read1` instances for 3 and 4-tuples.
+
 ## 4.15.0.0 *TBA*
 
   * `openFile` now calls the `open` system call with an `interruptible` FFI