ReaderWriterIO: instance Semigroup enables compatibility with GHC-8.4…

….1 (#168) * ReaderWriterIO: instance Semigroup enables compatibility with GHC-8.4.1 * Cabal: allow pqueue-1.4 * Prim.Types: Semigroup instances * Prim.Types: explicit import of Monoid compatibility with GHC-7.6.3 * Cabal.Test-Suite.Build-Depends: add semigroups package
HeinrichApfelmus · Mar 22, 2018 · d911162 · d911162
1 parent d42fb55
commit d911162
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Showing 3 changed files with 22 additions and 8 deletions.
diff --git a/reactive-banana/reactive-banana.cabal b/reactive-banana/reactive-banana.cabal
@@ -48,7 +48,7 @@ Library
                         vault == 0.3.*,
                         unordered-containers >= 0.2.1.0 && < 0.3,
                         hashable >= 1.1 && < 1.3,
-                        pqueue >= 1.0 && < 1.4
+                        pqueue >= 1.0 && < 1.5
 
     exposed-modules:
                         Control.Event.Handler,
@@ -85,5 +85,6 @@ Test-Suite tests
                         HUnit >= 1.2 && < 2,
                         test-framework >= 0.6 && < 0.9,
                         test-framework-hunit >= 0.2 && < 0.4,
-                        reactive-banana, vault, containers, transformers,
+                        reactive-banana, vault, containers,
+                        semigroups, transformers,
                         unordered-containers, hashable, psqueues, pqueue
diff --git a/reactive-banana/src/Control/Monad/Trans/ReaderWriterIO.hs b/reactive-banana/src/Control/Monad/Trans/ReaderWriterIO.hs
@@ -15,6 +15,7 @@ import Control.Monad.IO.Class
 import Control.Monad.Trans.Class
 import Data.IORef
 import Data.Monoid
+import Data.Semigroup
 
 {-----------------------------------------------------------------------------
     Type and class instances
@@ -35,6 +36,9 @@ instance MonadFix m => MonadFix (ReaderWriterIOT r w m) where mfix = mfixR
 instance MonadIO m => MonadIO (ReaderWriterIOT r w m)   where liftIO = liftIOR
 instance MonadTrans (ReaderWriterIOT r w)               where lift = liftR
 
+instance (Monad m, a ~ ()) => Semigroup (ReaderWriterIOT r w m a) where
+    mx <> my = mx >> my
+
 instance (Monad m, a ~ ()) => Monoid (ReaderWriterIOT r w m a) where
     mempty          = return ()
     mx `mappend` my = mx >> my

diff --git a/reactive-banana/src/Reactive/Banana/Prim/Types.hs b/reactive-banana/src/Reactive/Banana/Prim/Types.hs
@@ -10,7 +10,8 @@ import           Control.Monad.Trans.Reader
 import           Control.Monad.Trans.ReaderWriterIO
 import           Data.Functor
 import           Data.Hashable
-import           Data.Monoid
+import           Data.Monoid (Monoid, mempty, mappend)
+import           Data.Semigroup
 import qualified Data.Vault.Lazy                    as Lazy
 import           System.IO.Unsafe
 import           System.Mem.Weak
@@ -51,9 +52,12 @@ newtype BuildW = BuildW (DependencyBuilder, [Output], Action, Maybe (Build ()))
     --          , late build actions
     --          )
 
+instance Semigroup BuildW where
+    BuildW x <> BuildW y = BuildW (x <> y)
+
 instance Monoid BuildW where
-    mempty                          = BuildW mempty
-    (BuildW x) `mappend` (BuildW y) = BuildW (x `mappend` y)
+    mempty  = BuildW mempty
+    mappend = (<>)
 
 type BuildIO = Build
 
@@ -70,9 +74,11 @@ ground = 0
 
 -- | 'IO' actions as a monoid with respect to sequencing.
 newtype Action = Action { doit :: IO () }
+instance Semigroup Action where
+    Action x <> Action y = Action (x >> y)
 instance Monoid Action where
     mempty = Action $ return ()
-    (Action x) `mappend` (Action y) = Action (x >> y)
+    mappend = (<>)
 
 -- | Lens-like functionality.
 data Lens s a = Lens (s -> a) (a -> s -> s)
@@ -185,9 +191,12 @@ beginning = T 0
 next :: Time -> Time
 next (T n) = T (n+1)
 
+instance Semigroup Time where
+    T x <> T y = T (max x y)
+
 instance Monoid Time where
-    mappend (T x) (T y) = T (max x y)
-    mempty              = beginning
+    mappend = (<>)
+    mempty  = beginning
 
 {-----------------------------------------------------------------------------
     Notes