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Pull `Additive` into its own module

The getting base-orphans instances indirectly via monoidal is a sin we were already committing. It is just properly documented now. I would rather fix it separately.

commit807269ff4e4684a378348dfe65adad2b7ea36aff authorJohn Ericson <John.Ericson@Obsidian.Systems> dateWed 13 Oct 2021, 17:26 (5 years ago) parent0019cce
4 files changed+55−13
compare with develop
unifiedsplit
ChangeLog.md+3 patch.cabal+1 src/Data/Patch.hs+1−13 src/Data/Semigroup/Additive.hs+50
ChangeLog.md+3
@@ -2,6 +2,9 @@
22
33## Unreleased
44
5+* `Additive` now lives in `Data.Semigroup.Additive`, but is still reexported
6+ from `Data.Patch` for compatability.
7+
58* Rewrite `PatchMapWithMove` in terms of `PatchMapWithPatchingMove`.
69 Care is taken to make this not a breaking change.
710 In particular, `PatchMapWithMove` is a newtype of `PatchMapWithPatchingMove`, as is the `NodeInfo` and `From` of `PatchMapWithPatchingMove`'s versions of those.
patch.cabal+1
@@ -53,6 +53,7 @@ library
5353 , Data.Patch.Map
5454 , Data.Patch.MapWithMove
5555 , Data.Patch.MapWithPatchingMove
56+ , Data.Semigroup.Additive
5657
5758 ghc-options: -Wall -fwarn-redundant-constraints -fwarn-tabs
5859 default-extensions: PolyKinds
src/Data/Patch.hs+1−13
@@ -23,6 +23,7 @@ import Data.Semigroup (Semigroup (..))
2323#endif
2424import GHC.Generics
2525
26+import Data.Semigroup.Additive as X
2627import Data.Patch.Class as X
2728import Data.Patch.DMap as X hiding (getDeletions)
2829import Data.Patch.DMapWithMove as X
@@ -45,9 +46,6 @@ class (Semigroup q, Monoid q) => Group q where
4546 (~~) :: q -> q -> q
4647 r ~~ s = r <> negateG s
4748
48−-- | An 'Additive' 'Semigroup' is one where (<>) is commutative
49−class Semigroup q => Additive q where
50−
5149-- | The elements of an 'Additive' 'Semigroup' can be considered as patches of their own type.
5250newtype AdditivePatch p = AdditivePatch { unAdditivePatch :: p }
5351
@@ -58,19 +56,15 @@ instance Additive p => Patch (AdditivePatch p) where
5856instance (Ord k, Group q) => Group (MonoidalMap k q) where
5957 negateG = fmap negateG
6058
61−instance (Ord k, Additive q) => Additive (MonoidalMap k q)
62−
6359-- | Trivial group.
6460instance Group () where
6561 negateG _ = ()
6662 _ ~~ _ = ()
67−instance Additive ()
6863
6964-- | Product group. A Pair of groups gives rise to a group
7065instance (Group a, Group b) => Group (a, b) where
7166 negateG (a, b) = (negateG a, negateG b)
7267 (a, b) ~~ (c, d) = (a ~~ c, b ~~ d)
73−instance (Additive a, Additive b) => Additive (a, b)
7468
7569-- See https://gitlab.haskell.org/ghc/ghc/issues/11135#note_111802 for the reason Compose is not also provided.
7670-- Base does not define Monoid (Compose f g a) so this is the best we can
@@ -78,29 +72,23 @@ instance (Additive a, Additive b) => Additive (a, b)
7872instance Group (f (g a)) => Group ((f :.: g) a) where
7973 negateG (Comp1 xs) = Comp1 (negateG xs)
8074 Comp1 xs ~~ Comp1 ys = Comp1 (xs ~~ ys)
81−instance Additive (f (g a)) => Additive ((f :.: g) a)
8275
8376-- | Product of groups, Functor style.
8477instance (Group (f a), Group (g a)) => Group ((f :*: g) a) where
8578 negateG (a :*: b) = negateG a :*: negateG b
8679 (a :*: b) ~~ (c :*: d) = (a ~~ c) :*: (b ~~ d)
87−instance (Additive (f a), Additive (g a)) => Additive ((f :*: g) a)
8880
8981-- | Trivial group, Functor style
9082instance Group (Proxy x) where
9183 negateG _ = Proxy
9284 _ ~~ _ = Proxy
93−instance Additive (Proxy x)
9485
9586-- | Const lifts groups into a functor.
9687deriving instance Group a => Group (Const a x)
97−instance Additive a => Additive (Const a x)
9888-- | Ideitnty lifts groups pointwise (at only one point)
9989deriving instance Group a => Group (Identity a)
100−instance Additive a => Additive (Identity a)
10190
10291-- | Functions lift groups pointwise.
10392instance Group b => Group (a -> b) where
10493 negateG f = negateG . f
10594 (~~) = liftA2 (~~)
106−instance Additive b => Additive (a -> b)
src/Data/Semigroup/Additive.hsnew file+50
@@ -0,0 +1,50 @@
1+{-# LANGUAGE CPP #-}
2+{-# LANGUAGE TypeOperators #-}
3+{-# LANGUAGE TypeFamilies #-}
4+-- |
5+-- Module:
6+-- Data.Semigroup.Additive
7+-- Description:
8+-- This module defines a class for commutative semigroups, until it is moved
9+-- to another library.
10+module Data.Semigroup.Additive
11+ ( Additive
12+ ) where
13+
14+import Data.Functor.Const (Const (..))
15+import Data.Functor.Identity
16+-- For base-orphans, TODO don't cheat.
17+import Data.Map.Monoidal ()
18+import Data.Proxy
19+#if !MIN_VERSION_base(4,11,0)
20+import Data.Semigroup (Semigroup (..))
21+#endif
22+import GHC.Generics
23+
24+-- | An 'Additive' 'Semigroup' is one where (<>) is commutative
25+class Semigroup q => Additive q where
26+
27+-- | Trivial group.
28+instance Additive ()
29+
30+-- | Product group. A Pair of groups gives rise to a group
31+instance (Additive a, Additive b) => Additive (a, b)
32+
33+-- See https://gitlab.haskell.org/ghc/ghc/issues/11135#note_111802 for the reason Compose is not also provided.
34+-- Base does not define Monoid (Compose f g a) so this is the best we can
35+-- really do for functor composition.
36+instance Additive (f (g a)) => Additive ((f :.: g) a)
37+
38+-- | Product of groups, Functor style.
39+instance (Additive (f a), Additive (g a)) => Additive ((f :*: g) a)
40+
41+-- | Trivial group, Functor style
42+instance Additive (Proxy x)
43+
44+-- | Const lifts groups into a functor.
45+instance Additive a => Additive (Const a x)
46+-- | Ideitnty lifts groups pointwise (at only one point)
47+instance Additive a => Additive (Identity a)
48+
49+-- | Functions lift groups pointwise.
50+instance Additive b => Additive (a -> b)