From a0fe6f6c779c66a8e61b3103ebc97871b8012f9e Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Mon, 7 Dec 2020 12:07:39 -0500
Subject: [PATCH] Remove Group which is not needed by this library

This is a breaking change here, but need not be a breaking change for Reflex.

The version in the cabal file is bumped to remind whoever does the
future release that this is breaking change.

Closes #4 as far as this library is concerned, though work is still
needed on the Reflex side when supported the new patch version to fix
this issue for real.
---
 ChangeLog.md      |  8 +++++
 patch.cabal       | 16 ++--------
 src/Data/Patch.hs | 79 +----------------------------------------------
 3 files changed, 11 insertions(+), 92 deletions(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index 6223cc06..f1109731 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,13 @@
 # Revision history for patch
 
+## Unreleased
+
+* Remove `Group`, which is unused by the rest of this library and best defined elsewhere.
+  It shouldn't have been included when this library was split from `reflex`.
+
+* Remove the `split-these` flag.
+  We no longer need it as we only use the `These` datatype which is provided in all versions.
+
 ## 0.0.3.2
 
 * Update version bounds
diff --git a/patch.cabal b/patch.cabal
index 53072e7a..27a41611 100644
--- a/patch.cabal
+++ b/patch.cabal
@@ -1,5 +1,5 @@
 Name: patch
-Version: 0.0.3.2
+Version: 0.1.0.0
 Synopsis: Data structures for describing changes to other data structures.
 Description:
   Data structures for describing changes to other data structures.
@@ -25,11 +25,6 @@ tested-with:
   GHC ==8.0.2 || ==8.2.2 || ==8.4.4 || ==8.6.5 || ==8.8.1
   GHCJS ==8.4
 
-flag split-these
-  description: Use split these/semialign packages
-  manual:      False
-  default:     True
-
 library
   hs-source-dirs: src
   default-language: Haskell2010
@@ -40,6 +35,7 @@ library
                , dependent-sum >= 0.6 && < 0.8
                , lens >= 4.7 && < 5
                , semigroupoids >= 4.0 && < 6
+               , these >= 0.4 && < 1.2
                , transformers >= 0.5.6.0 && < 0.6
                , witherable >= 0.3 && < 0.4
 
@@ -56,14 +52,6 @@ library
 
   ghc-options: -Wall -fwarn-redundant-constraints -fwarn-tabs
 
-  if flag(split-these)
-    build-depends: these >= 1 && <1.2
-                 , semialign >=1 && <1.2
-                 , monoidal-containers >= 0.6 && < 0.7
-  else
-    build-depends: these >= 0.4 && <0.9
-                 , monoidal-containers == 0.4.0.0
-
 test-suite hlint
   default-language: Haskell2010
   type: exitcode-stdio-1.0
diff --git a/src/Data/Patch.hs b/src/Data/Patch.hs
index 7b6eb85e..da62065c 100644
--- a/src/Data/Patch.hs
+++ b/src/Data/Patch.hs
@@ -9,20 +9,9 @@
 -- Description:
 --   This module defines the 'Patch' class.
 module Data.Patch
-  ( module Data.Patch
-  , module X
+  ( module X
   ) where
 
-import Control.Applicative
-import Data.Functor.Const (Const (..))
-import Data.Functor.Identity
-import Data.Map.Monoidal (MonoidalMap)
-import Data.Proxy
-#if !MIN_VERSION_base(4,11,0)
-import Data.Semigroup (Semigroup (..))
-#endif
-import GHC.Generics
-
 import Data.Patch.Class as X
 import Data.Patch.DMap as X hiding (getDeletions)
 import Data.Patch.DMapWithMove as X
@@ -38,69 +27,3 @@ import Data.Patch.MapWithMove as X
   , patchMapWithMoveNewElementsMap, unPatchMapWithMove
   , unsafePatchMapWithMove
   )
-
--- | A 'Group' is a 'Monoid' where every element has an inverse.
-class (Semigroup q, Monoid q) => Group q where
-  negateG :: q -> q
-  (~~) :: q -> q -> q
-  r ~~ s = r <> negateG s
-
--- | An 'Additive' 'Semigroup' is one where (<>) is commutative
-class Semigroup q => Additive q where
-
--- | The elements of an 'Additive' 'Semigroup' can be considered as patches of their own type.
-newtype AdditivePatch p = AdditivePatch { unAdditivePatch :: p }
-
-instance Additive p => Patch (AdditivePatch p) where
-  type PatchTarget (AdditivePatch p) = p
-  apply (AdditivePatch p) q = Just $ p <> q
-
-instance (Ord k, Group q) => Group (MonoidalMap k q) where
-  negateG = fmap negateG
-
-instance (Ord k, Additive q) => Additive (MonoidalMap k q)
-
--- | Trivial group.
-instance Group () where
-  negateG _ = ()
-  _ ~~ _ = ()
-instance Additive ()
-
--- | Product group.  A Pair of groups gives rise to a group
-instance (Group a, Group b) => Group (a, b) where
-  negateG (a, b) = (negateG a, negateG b)
-  (a, b) ~~ (c, d) = (a ~~ c, b ~~ d)
-instance (Additive a, Additive b) => Additive (a, b)
-
--- See https://gitlab.haskell.org/ghc/ghc/issues/11135#note_111802 for the reason Compose is not also provided.
--- Base does not define Monoid (Compose f g a) so this is the best we can
--- really do for functor composition.
-instance Group (f (g a)) => Group ((f :.: g) a) where
-  negateG (Comp1 xs) = Comp1 (negateG xs)
-  Comp1 xs ~~ Comp1 ys = Comp1 (xs ~~ ys)
-instance Additive (f (g a)) => Additive ((f :.: g) a)
-
--- | Product of groups, Functor style.
-instance (Group (f a), Group (g a)) => Group ((f :*: g) a) where
-  negateG (a :*: b) = negateG a :*: negateG b
-  (a :*: b) ~~ (c :*: d) = (a ~~ c) :*: (b ~~ d)
-instance (Additive (f a), Additive (g a)) => Additive ((f :*: g) a)
-
--- | Trivial group, Functor style
-instance Group (Proxy x) where
-  negateG _ = Proxy
-  _ ~~ _ = Proxy
-instance Additive (Proxy x)
-
--- | Const lifts groups into a functor.
-deriving instance Group a => Group (Const a x)
-instance Additive a => Additive (Const a x)
--- | Ideitnty lifts groups pointwise (at only one point)
-deriving instance Group a => Group (Identity a)
-instance Additive a => Additive (Identity a)
-
--- | Functions lift groups pointwise.
-instance Group b => Group (a -> b) where
-  negateG f = negateG . f
-  (~~) = liftA2 (~~)
-instance Additive b => Additive (a -> b)