From 0b2b27ff218f08178536cdb41136e1dffe8619b4 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 16:40:56 -0400
Subject: [PATCH 01/17] Stub in an AppMerge semigroup.

---
 semantic.cabal            | 1 +
 src/Data/Semigroup/App.hs | 7 +++++++
 2 files changed, 8 insertions(+)
 create mode 100644 src/Data/Semigroup/App.hs

diff --git a/semantic.cabal b/semantic.cabal
index 132722e06..9b8c4b9af 100644
--- a/semantic.cabal
+++ b/semantic.cabal
@@ -72,6 +72,7 @@ library
                      , Data.Patch
                      , Data.Range
                      , Data.Record
+                     , Data.Semigroup.App
                      , Data.Source
                      , Data.Span
                      , Data.SplitDiff
diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
new file mode 100644
index 000000000..7f183d5eb
--- /dev/null
+++ b/src/Data/Semigroup/App.hs
@@ -0,0 +1,7 @@
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module Data.Semigroup.App where
+
+import Control.Applicative
+
+newtype AppMerge f a = AppMerge { runAppMerge :: f a }
+  deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)

From 541e23043148cc626c15de951c6eb16c80b60eb7 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 16:41:32 -0400
Subject: [PATCH 02/17] Define a Semigroup instance for AppMerge.

---
 src/Data/Semigroup/App.hs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 7f183d5eb..07d5c0ec0 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -2,6 +2,10 @@
 module Data.Semigroup.App where
 
 import Control.Applicative
+import Data.Semigroup
 
 newtype AppMerge f a = AppMerge { runAppMerge :: f a }
   deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)
+
+instance (Applicative f, Semigroup a) => Semigroup (AppMerge f a) where
+  AppMerge a <> AppMerge b = AppMerge ((<>) <$> a <*> b)

From 794a03a49c124887ff3b3a172386d76688fda05b Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 16:41:41 -0400
Subject: [PATCH 03/17] :memo: AppMerge.

---
 src/Data/Semigroup/App.hs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 07d5c0ec0..9b393f126 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -4,6 +4,7 @@ module Data.Semigroup.App where
 import Control.Applicative
 import Data.Semigroup
 
+-- | 'Semigroup' under '<*>' and '<>'.
 newtype AppMerge f a = AppMerge { runAppMerge :: f a }
   deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)
 

From 88230df1fe910acd5c7cf4840313b488413f90b5 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 16:41:49 -0400
Subject: [PATCH 04/17] Define a Monoid instance for AppMerge.

---
 src/Data/Semigroup/App.hs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 9b393f126..639c1c87c 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -10,3 +10,7 @@ newtype AppMerge f a = AppMerge { runAppMerge :: f a }
 
 instance (Applicative f, Semigroup a) => Semigroup (AppMerge f a) where
   AppMerge a <> AppMerge b = AppMerge ((<>) <$> a <*> b)
+
+instance (Applicative f, Monoid a, Semigroup a) => Monoid (AppMerge f a) where
+  mempty = AppMerge (pure mempty)
+  mappend = (<>)

From 8f22cb26f885e9a302a0233de71cc5bea62cc724 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 16:44:35 -0400
Subject: [PATCH 05/17] Explicitly list the exports.

---
 src/Data/Semigroup/App.hs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 639c1c87c..875d3319d 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -1,5 +1,7 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
-module Data.Semigroup.App where
+module Data.Semigroup.App
+( AppMerge(..)
+) where
 
 import Control.Applicative
 import Data.Semigroup

From 6399cb3c58a3d0963b58331f266e2d36c7a452d8 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:07:49 -0400
Subject: [PATCH 06/17] Define an App semigroup.

---
 src/Data/Semigroup/App.hs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 875d3319d..6fec42eb1 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -1,6 +1,7 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 module Data.Semigroup.App
 ( AppMerge(..)
+, App(..)
 ) where
 
 import Control.Applicative
@@ -16,3 +17,7 @@ instance (Applicative f, Semigroup a) => Semigroup (AppMerge f a) where
 instance (Applicative f, Monoid a, Semigroup a) => Monoid (AppMerge f a) where
   mempty = AppMerge (pure mempty)
   mappend = (<>)
+
+
+newtype App f a = App { runApp :: f a }
+  deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)

From 5ea6482e96571f026780686f0c7d1068f3460ea1 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:07:55 -0400
Subject: [PATCH 07/17] :memo: App.

---
 src/Data/Semigroup/App.hs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 6fec42eb1..4708edb27 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -19,5 +19,6 @@ instance (Applicative f, Monoid a, Semigroup a) => Monoid (AppMerge f a) where
   mappend = (<>)
 
 
+-- | 'Semigroup' under '*>'.
 newtype App f a = App { runApp :: f a }
   deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)

From 3329bd0a5176ca5d17f39b9e39497368895d6ddd Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:08:06 -0400
Subject: [PATCH 08/17] Define a Semigroup instance for App.

---
 src/Data/Semigroup/App.hs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 4708edb27..4218a110c 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -22,3 +22,6 @@ instance (Applicative f, Monoid a, Semigroup a) => Monoid (AppMerge f a) where
 -- | 'Semigroup' under '*>'.
 newtype App f a = App { runApp :: f a }
   deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)
+
+instance Applicative f => Semigroup (App f a) where
+  App a <> App b = App (a *> b)

From e0245ed7524cbfbbb0021769a2642d037ced7680 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:08:14 -0400
Subject: [PATCH 09/17] Define a Monoid instance for App.

---
 src/Data/Semigroup/App.hs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 4218a110c..414ce1c9b 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -25,3 +25,7 @@ newtype App f a = App { runApp :: f a }
 
 instance Applicative f => Semigroup (App f a) where
   App a <> App b = App (a *> b)
+
+instance (Applicative f, Monoid a) => Monoid (App f a) where
+  mempty = App (pure mempty)
+  mappend = (<>)

From 256623a81816f02703d336d246febe8fd50a8f90 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:08:25 -0400
Subject: [PATCH 10/17] eval lists in App.

---
 src/Data/Abstract/Evaluatable.hs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Data/Abstract/Evaluatable.hs b/src/Data/Abstract/Evaluatable.hs
index adf41de29..21d7c6a98 100644
--- a/src/Data/Abstract/Evaluatable.hs
+++ b/src/Data/Abstract/Evaluatable.hs
@@ -16,6 +16,7 @@ import Data.Abstract.Value
 import Data.Functor.Classes
 import Data.Proxy
 import Data.Semigroup.Foldable
+import Data.Semigroup.App
 import Data.Term
 import Prelude hiding (fail)
 import Prologue
@@ -51,7 +52,7 @@ instance Evaluatable s => Evaluatable (TermF s a) where
 --   3. Only the last statement’s return value is returned.
 instance Evaluatable [] where
   -- 'nonEmpty' and 'foldMap1' enable us to return the last statement’s result instead of 'unit' for non-empty lists.
-  eval = maybe unit (runImperative . foldMap1 (Imperative . subtermValue)) . nonEmpty
+  eval = maybe unit (runApp . foldMap1 (App . subtermValue)) . nonEmpty
 
 -- | A 'Semigroup' providing an imperative context which extends the local environment with new bindings.
 newtype Imperative m a = Imperative { runImperative :: m a }

From 69a4e4cc2eff281725274f3bff8018e0bb8e9fa8 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:08:52 -0400
Subject: [PATCH 11/17] :fire: Imperative.

---
 src/Data/Abstract/Evaluatable.hs | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/src/Data/Abstract/Evaluatable.hs b/src/Data/Abstract/Evaluatable.hs
index 21d7c6a98..c4cb0ff63 100644
--- a/src/Data/Abstract/Evaluatable.hs
+++ b/src/Data/Abstract/Evaluatable.hs
@@ -53,13 +53,3 @@ instance Evaluatable s => Evaluatable (TermF s a) where
 instance Evaluatable [] where
   -- 'nonEmpty' and 'foldMap1' enable us to return the last statement’s result instead of 'unit' for non-empty lists.
   eval = maybe unit (runApp . foldMap1 (App . subtermValue)) . nonEmpty
-
--- | A 'Semigroup' providing an imperative context which extends the local environment with new bindings.
-newtype Imperative m a = Imperative { runImperative :: m a }
-
-instance MonadEnvironment value m => Semigroup (Imperative m a) where
-  Imperative a <> Imperative b = Imperative (a *> b)
-
-instance (MonadEnvironment value m, MonadValue value m) => Monoid (Imperative m value) where
-  mempty = Imperative unit
-  mappend = (<>)

From c6148c6cad3f5322ab5a6bcc54f6319fb1815859 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:16:09 -0400
Subject: [PATCH 12/17] Test the associativity of the semigroup instances.

---
 src/Data/Semigroup/App.hs | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 414ce1c9b..78922f68c 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -7,10 +7,17 @@ module Data.Semigroup.App
 import Control.Applicative
 import Data.Semigroup
 
+-- $setup
+-- >>> import Test.QuickCheck
+-- >>> instance Arbitrary (f a) => Arbitrary (App f a) where arbitrary = App <$> arbitrary
+-- >>> instance Arbitrary (f a) => Arbitrary (AppMerge f a) where arbitrary = AppMerge <$> arbitrary
+
 -- | 'Semigroup' under '<*>' and '<>'.
 newtype AppMerge f a = AppMerge { runAppMerge :: f a }
   deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)
 
+-- $ Associativity:
+--   prop> \ a b c -> a <> (b <> c) == (a <> b) <> (c :: AppMerge Maybe String)
 instance (Applicative f, Semigroup a) => Semigroup (AppMerge f a) where
   AppMerge a <> AppMerge b = AppMerge ((<>) <$> a <*> b)
 
@@ -23,6 +30,8 @@ instance (Applicative f, Monoid a, Semigroup a) => Monoid (AppMerge f a) where
 newtype App f a = App { runApp :: f a }
   deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)
 
+-- $ Associativity:
+--   prop> \ a b c -> a <> (b <> c) == (a <> b) <> (c :: App Maybe Integer)
 instance Applicative f => Semigroup (App f a) where
   App a <> App b = App (a *> b)
 

From 6be056bd9ad6ac5fdce2b38754932d77a2b43255 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:16:31 -0400
Subject: [PATCH 13/17] Swap the order of the types.

---
 src/Data/Semigroup/App.hs | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 78922f68c..8292024e7 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -1,7 +1,7 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 module Data.Semigroup.App
-( AppMerge(..)
-, App(..)
+( App(..)
+, AppMerge(..)
 ) where
 
 import Control.Applicative
@@ -12,20 +12,6 @@ import Data.Semigroup
 -- >>> instance Arbitrary (f a) => Arbitrary (App f a) where arbitrary = App <$> arbitrary
 -- >>> instance Arbitrary (f a) => Arbitrary (AppMerge f a) where arbitrary = AppMerge <$> arbitrary
 
--- | 'Semigroup' under '<*>' and '<>'.
-newtype AppMerge f a = AppMerge { runAppMerge :: f a }
-  deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)
-
--- $ Associativity:
---   prop> \ a b c -> a <> (b <> c) == (a <> b) <> (c :: AppMerge Maybe String)
-instance (Applicative f, Semigroup a) => Semigroup (AppMerge f a) where
-  AppMerge a <> AppMerge b = AppMerge ((<>) <$> a <*> b)
-
-instance (Applicative f, Monoid a, Semigroup a) => Monoid (AppMerge f a) where
-  mempty = AppMerge (pure mempty)
-  mappend = (<>)
-
-
 -- | 'Semigroup' under '*>'.
 newtype App f a = App { runApp :: f a }
   deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)
@@ -38,3 +24,17 @@ instance Applicative f => Semigroup (App f a) where
 instance (Applicative f, Monoid a) => Monoid (App f a) where
   mempty = App (pure mempty)
   mappend = (<>)
+
+
+-- | 'Semigroup' under '<*>' and '<>'.
+newtype AppMerge f a = AppMerge { runAppMerge :: f a }
+  deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)
+
+-- $ Associativity:
+--   prop> \ a b c -> a <> (b <> c) == (a <> b) <> (c :: AppMerge Maybe String)
+instance (Applicative f, Semigroup a) => Semigroup (AppMerge f a) where
+  AppMerge a <> AppMerge b = AppMerge ((<>) <$> a <*> b)
+
+instance (Applicative f, Monoid a, Semigroup a) => Monoid (AppMerge f a) where
+  mempty = AppMerge (pure mempty)
+  mappend = (<>)

From b55010c2c1e5339bd311287a28dd10ec329a98a7 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:22:34 -0400
Subject: [PATCH 14/17] Define shrinking.

---
 src/Data/Semigroup/App.hs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 8292024e7..506fafe80 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -9,8 +9,8 @@ import Data.Semigroup
 
 -- $setup
 -- >>> import Test.QuickCheck
--- >>> instance Arbitrary (f a) => Arbitrary (App f a) where arbitrary = App <$> arbitrary
--- >>> instance Arbitrary (f a) => Arbitrary (AppMerge f a) where arbitrary = AppMerge <$> arbitrary
+-- >>> instance Arbitrary (f a) => Arbitrary (App f a) where arbitrary = App <$> arbitrary ; shrink = map App . shrink . runApp
+-- >>> instance Arbitrary (f a) => Arbitrary (AppMerge f a) where arbitrary = AppMerge <$> arbitrary ; shrink = map AppMerge . shrink . runAppMerge
 
 -- | 'Semigroup' under '*>'.
 newtype App f a = App { runApp :: f a }

From aab509cf63ea1d858e39b64f75f00c79a2a2c6f2 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:26:07 -0400
Subject: [PATCH 15/17] Test the identity properties.

---
 src/Data/Semigroup/App.hs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 506fafe80..ccd10f4f5 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -21,6 +21,9 @@ newtype App f a = App { runApp :: f a }
 instance Applicative f => Semigroup (App f a) where
   App a <> App b = App (a *> b)
 
+-- $ Identity:
+--   prop> \ a -> mempty <> a == (a :: App Maybe String)
+--   prop> \ a -> a <> mempty == (a :: App Maybe String)
 instance (Applicative f, Monoid a) => Monoid (App f a) where
   mempty = App (pure mempty)
   mappend = (<>)
@@ -35,6 +38,9 @@ newtype AppMerge f a = AppMerge { runAppMerge :: f a }
 instance (Applicative f, Semigroup a) => Semigroup (AppMerge f a) where
   AppMerge a <> AppMerge b = AppMerge ((<>) <$> a <*> b)
 
+-- $ Identity:
+--   prop> \ a -> mempty <> a == (a :: AppMerge Maybe String)
+--   prop> \ a -> a <> mempty == (a :: AppMerge Maybe String)
 instance (Applicative f, Monoid a, Semigroup a) => Monoid (AppMerge f a) where
   mempty = AppMerge (pure mempty)
   mappend = (<>)

From 6a785e0b30beb64d8feda6666f54a36c7816b8d4 Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:26:32 -0400
Subject: [PATCH 16/17] =?UTF-8?q?Remove=20the=20Monoid=20instance=20for=20?=
 =?UTF-8?q?App,=20as=20it=E2=80=99s=20unlawful.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/Data/Semigroup/App.hs | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index ccd10f4f5..58d666076 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -21,13 +21,6 @@ newtype App f a = App { runApp :: f a }
 instance Applicative f => Semigroup (App f a) where
   App a <> App b = App (a *> b)
 
--- $ Identity:
---   prop> \ a -> mempty <> a == (a :: App Maybe String)
---   prop> \ a -> a <> mempty == (a :: App Maybe String)
-instance (Applicative f, Monoid a) => Monoid (App f a) where
-  mempty = App (pure mempty)
-  mappend = (<>)
-
 
 -- | 'Semigroup' under '<*>' and '<>'.
 newtype AppMerge f a = AppMerge { runAppMerge :: f a }

From d645481dcfd182b2d3fbd5d68359087d3bd4838b Mon Sep 17 00:00:00 2001
From: Rob Rix <rob.rix@me.com>
Date: Wed, 21 Mar 2018 17:29:48 -0400
Subject: [PATCH 17/17] :memo: AppMerge is a Monoid too.

---
 src/Data/Semigroup/App.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Data/Semigroup/App.hs b/src/Data/Semigroup/App.hs
index 58d666076..4ed13ff3c 100644
--- a/src/Data/Semigroup/App.hs
+++ b/src/Data/Semigroup/App.hs
@@ -22,7 +22,7 @@ instance Applicative f => Semigroup (App f a) where
   App a <> App b = App (a *> b)
 
 
--- | 'Semigroup' under '<*>' and '<>'.
+-- | 'Semigroup' and 'Monoid' under '<*>' and '<>'.
 newtype AppMerge f a = AppMerge { runAppMerge :: f a }
   deriving (Alternative, Applicative, Bounded, Enum, Eq, Foldable, Functor, Monad, Ord, Show, Traversable)