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-rw-r--r--libraries/base/Data/Functor/Classes.hs10
-rw-r--r--libraries/base/tests/T19719.hs26
-rw-r--r--libraries/base/tests/T19719.stdout16
-rw-r--r--libraries/base/tests/all.T1
4 files changed, 50 insertions, 3 deletions
diff --git a/libraries/base/Data/Functor/Classes.hs b/libraries/base/Data/Functor/Classes.hs
index 6a0d008982..d672c340d7 100644
--- a/libraries/base/Data/Functor/Classes.hs
+++ b/libraries/base/Data/Functor/Classes.hs
@@ -848,11 +848,13 @@ instance Eq1 Complex where
-- [(2 % 3 :+ 3 % 4,"")]
--
instance Read1 Complex where
- liftReadPrec rp _ = parens $ prec 9 $ do
+ liftReadPrec rp _ = parens $ prec complexPrec $ do
x <- step rp
expectP (Symbol ":+")
y <- step rp
return (x :+ y)
+ where
+ complexPrec = 6
liftReadListPrec = liftReadListPrecDefault
liftReadList = liftReadListDefault
@@ -863,8 +865,10 @@ instance Read1 Complex where
-- "2 :+ 3"
--
instance Show1 Complex where
- liftShowsPrec sp _ d (x :+ y) = showParen (d >= 10) $
- sp 10 x . showString " :+ " . sp 10 y
+ liftShowsPrec sp _ d (x :+ y) = showParen (d > complexPrec) $
+ sp (complexPrec+1) x . showString " :+ " . sp (complexPrec+1) y
+ where
+ complexPrec = 6
-- Building blocks
diff --git a/libraries/base/tests/T19719.hs b/libraries/base/tests/T19719.hs
new file mode 100644
index 0000000000..613f92ad6c
--- /dev/null
+++ b/libraries/base/tests/T19719.hs
@@ -0,0 +1,26 @@
+module Main (main) where
+
+import Data.Complex (Complex(..))
+import Data.Functor.Classes (readPrec1, showsPrec1)
+import Text.ParserCombinators.ReadPrec (readPrec_to_S)
+import Text.Read (Read(..))
+
+comp :: Complex Int
+comp = 1 :+ 1
+
+compareInstances :: Int -> IO ()
+compareInstances p = do
+ let precBanner = " (at precedence " ++ show p ++ ")"
+ putStrLn $ "Read vs. Read1" ++ precBanner
+ print (readPrec_to_S readPrec p "1 :+ 1" :: [(Complex Int, String)])
+ print (readPrec_to_S readPrec1 p "1 :+ 1" :: [(Complex Int, String)])
+ putStrLn ""
+ putStrLn $ "Show vs. Show1" ++ precBanner
+ putStrLn $ showsPrec p comp ""
+ putStrLn $ showsPrec1 p comp ""
+ putStrLn ""
+
+main :: IO ()
+main = do
+ compareInstances 6
+ compareInstances 7
diff --git a/libraries/base/tests/T19719.stdout b/libraries/base/tests/T19719.stdout
new file mode 100644
index 0000000000..8f59bd40f0
--- /dev/null
+++ b/libraries/base/tests/T19719.stdout
@@ -0,0 +1,16 @@
+Read vs. Read1 (at precedence 6)
+[(1 :+ 1,"")]
+[(1 :+ 1,"")]
+
+Show vs. Show1 (at precedence 6)
+1 :+ 1
+1 :+ 1
+
+Read vs. Read1 (at precedence 7)
+[]
+[]
+
+Show vs. Show1 (at precedence 7)
+(1 :+ 1)
+(1 :+ 1)
+
diff --git a/libraries/base/tests/all.T b/libraries/base/tests/all.T
index b02d77ef11..7ea69949e2 100644
--- a/libraries/base/tests/all.T
+++ b/libraries/base/tests/all.T
@@ -263,3 +263,4 @@ test('T16643', normal, compile_and_run, [''])
test('clamp', normal, compile_and_run, [''])
test('T18642', extra_run_opts('+RTS -T -RTS'), compile_and_run, ['-O2'])
test('T19288', exit_code(1), compile_and_run, [''])
+test('T19719', normal, compile_and_run, [''])