refactor the pair matcher

Author: egisatoshi

src/Control/Egison/Matcher/Collection.hs

@@ -181,7 +181,7 @@ eqAs :: (Matcher m1 t1, Matcher m2 t2,
 eqAs m1 m2 xs ys = match
   dfs
   (xs, ys)
-  (Pair m1 m2)
+  (m1, m2)
   [ [mc| ([], []) -> True |]
   , [mc| ($x : $xs, #x : $ys) -> eqAs m1 m2 xs ys |]
   , [mc| _ -> False |]

src/Control/Egison/Matcher/Pair.hs

@@ -5,8 +5,7 @@
 -- Stability:   experimental
 
 module Control.Egison.Matcher.Pair
-  ( Pair(..)
-  , tuple2
+  ( tuple2
   , tuple2M
   )
 where
@@ -17,18 +16,16 @@ import           Control.Egison.Match
 import           Control.Egison.Matcher
 import           Control.Egison.QQ
 
-data Pair m1 m2 = Pair m1 m2
+instance (Matcher m1 t1, Matcher m2 t2) => Matcher (m1, m2) (t1, t2)
 
-instance (Matcher m1 t1, Matcher m2 t2) => Matcher (Pair m1 m2) (t1, t2)
+tuple2 :: Pattern (PP t1, PP t2) (m1, m2) (t1, t2) (t1, t2)
+tuple2 _ (_, _) (t1, t2) = pure (t1, t2)
 
-tuple2 :: Pattern (PP t1, PP t2) (Pair m1 m2) (t1, t2) (t1, t2)
-tuple2 _ (Pair _ _) (t1, t2) = pure (t1, t2)
+tuple2M :: (m1, m2) -> (t1, t2) -> (m1, m2)
+tuple2M (m1, m2) _ = (m1, m2)
 
-tuple2M :: Pair m1 m2 -> (t1, t2) -> (m1, m2)
-tuple2M (Pair m1 m2) _ = (m1, m2)
-
-instance (Eq a1, Matcher m1 a1, ValuePattern m1 a1, Eq a2, Matcher m2 a2, ValuePattern m2 a2) => ValuePattern (Pair m1 m2) (a1, a2) where
-  value (e1, e2) () (Pair m1 m2) (v1, v2) =
+instance (Eq a1, Matcher m1 a1, ValuePattern m1 a1, Eq a2, Matcher m2 a2, ValuePattern m2 a2) => ValuePattern (m1, m2) (a1, a2) where
+  value (e1, e2) () (m1, m2) (v1, v2) =
     if eqAs m1 e1 v1 && eqAs m2 e2 v2 then pure () else mzero
 
 eqAs :: (Matcher m t, ValuePattern m t) => m -> t -> t -> Bool

test/Control/EgisonSpec.hs

@@ -42,7 +42,7 @@ test_pair =
   [ testCase "pair" $ assertEqual "simple" (1, 2) $ match
       dfs
       (1, 2)
-      (Pair Something Something)
+      (Something, Something)
       [[mc| ($x, $y) -> (x, y) |]]
   ]