Add Ord instances for Interval, IntervalSet and IntervalMap

The primary intended use case for these is to allow storage in maps and
sets.

src/Data/Interval/Internal.hs

@@ -55,7 +55,14 @@ data Interval r
   | LeftOpen !r !r
   | RightOpen !r !r
   | BothOpen !r !r
-  deriving (Eq, Typeable)
+  deriving
+    ( Eq,
+      Ord,
+      -- ^ Note that this Ord is derived and not semantically meaningful.
+      -- The primary intended use case is to allow using 'Interval'
+      -- in maps and sets that require ordering.
+      Typeable
+    )
 
 peekInterval :: (Applicative m, Monad m, Ord r) => m Int8 -> m r -> m r -> m (Interval r)
 peekInterval tagM x y = do

src/Data/IntervalMap/Base.hs

@@ -123,7 +123,14 @@ import qualified GHC.Exts as GHCExts
 -- Unlike 'IntervalSet', 'IntervalMap' never merge adjacent mappings,
 -- even if adjacent intervals are connected and mapped to the same value.
 newtype IntervalMap r a = IntervalMap (Map (LB r) (Interval r, a))
-  deriving (Eq, Typeable)
+  deriving
+    ( Eq,
+      Ord,
+      -- ^ Note that this Ord is derived and not semantically meaningful.
+      -- The primary intended use case is to allow using 'IntervalSet'
+      -- in maps and sets that require ordering.
+      Typeable
+    )
 
 #if __GLASGOW_HASKELL__ >= 708
 type role IntervalMap nominal representational

src/Data/IntervalSet.hs

@@ -88,7 +88,14 @@ import qualified GHC.Exts as GHCExts
 --
 -- Any connected intervals are merged together, and empty intervals are ignored.
 newtype IntervalSet r = IntervalSet (Map (Extended r) (Interval r))
-  deriving (Eq, Typeable)
+  deriving
+    ( Eq,
+      Ord,
+      -- ^ Note that this Ord is derived and not semantically meaningful.
+      -- The primary intended use case is to allow using 'IntervalSet'
+      -- in maps and sets that require ordering.
+      Typeable
+    )
 
 #if __GLASGOW_HASKELL__ >= 708
 type role IntervalSet nominal