Move Unzip to the bottom of type-class hierarchy

Every Functor can be Unzip. Some can be more efficient than default.

Author: phadej

semialign/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 1.4
+
+- Reorder class hierarchy. `Unzip` is now at the bottom, right above `Functor`.
+
 # 1.3.1
 
 - Support GHC-8.6.5...GHC-9.10.1

semialign/semialign.cabal

@@ -1,7 +1,6 @@
 cabal-version:      >=1.10
 name:               semialign
-version:            1.3.1
-x-revision:         1
+version:            1.4
 synopsis:
   Align and Zip type-classes from the common Semialign ancestor.
 

semialign/src/Data/Semialign/Internal.hs

@@ -121,7 +121,7 @@ oops = error . ("Data.Align: internal error: " ++)
 --          ≡ mapMaybe justHere (toList (align x y))
 -- @
 --
-class Functor f => Semialign f where
+class Unzip f => Semialign f where
     -- | Analogous to @'zip'@, combines two structures by taking the union of
     --   their shapes and using @'These'@ to hold the elements.
     align :: f a -> f b -> f (These a b)
@@ -295,7 +295,7 @@ class Zip f => Repeat f where
 --
 -- For sequence-like types this holds, but for Map-like it doesn't.
 --
-class Zip f => Unzip f where
+class Functor f => Unzip f where
     unzipWith :: (c -> (a, b)) -> f c -> (f a, f b)
     unzipWith f = unzip . fmap f
 
@@ -337,6 +337,12 @@ class (ZipWithIndex i f, Repeat f) => RepeatWithIndex i f | f -> i where
 -- base
 -------------------------------------------------------------------------------
 
+-- |
+--
+-- @since 1.4
+instance Unzip ((->) e) where
+    unzip = unzipDefault
+
 instance Semialign ((->) e) where
     align f g x = These (f x) (g x)
     alignWith h f g x = h (These (f x) (g x))
@@ -661,6 +667,13 @@ instance (RepeatWithIndex i f, RepeatWithIndex j g) => RepeatWithIndex (i, j) (C
 -------------------------------------------------------------------------------
 
 -- Based on the Data.Vector.Fusion.Stream.Monadic zipWith implementation
+
+-- |
+--
+-- @since 1.4
+instance Monad m => Unzip (Stream m) where
+    unzip = unzipDefault
+
 instance Monad m => Align (Stream m) where
     nil = Stream.empty
 
@@ -688,9 +701,16 @@ instance Monad m => Semialign (Stream m) where
                     _               -> Skip (sa, sb, Nothing, False)
 #endif
 
+
 instance Monad m => Zip (Stream m) where
     zipWith = Stream.zipWith
 
+-- |
+--
+-- @since 1.4
+instance Monad m => Unzip (Bundle m v) where
+    unzip = unzipDefault
+
 instance Monad m => Align (Bundle m v) where
     nil = Bundle.empty