fix #4876

[ghc-base.git] / Data / Complex.hs

diff --git a/Data/Complex.hs b/Data/Complex.hs
index 60ee834..6965547 100644 (file)
--- a/Data/Complex.hs
+++ b/Data/Complex.hs
@@ -44,6 +44,9 @@ module Data.Complex
 import Prelude
 
 import Data.Typeable
+#ifdef __GLASGOW_HASKELL__
+import Data.Data (Data)
+#endif
 
 #ifdef __HUGS__
 import Hugs.Prelude(Num(fromInt), Fractional(fromDouble))
@@ -62,7 +65,11 @@ infix  6  :+
 data (RealFloat a) => Complex a
   = !a :+ !a    -- ^ forms a complex number from its real and imaginary
                 -- rectangular components.
+# if __GLASGOW_HASKELL__
+        deriving (Eq, Show, Read, Data)
+# else
         deriving (Eq, Show, Read)
+# endif
 
 -- -----------------------------------------------------------------------------
 -- Functions over Complex
@@ -191,4 +198,4 @@ instance  (RealFloat a) => Floating (Complex a) where
 
     asinh z        =  log (z + sqrt (1+z*z))
     acosh z        =  log (z + (z+1) * sqrt ((z-1)/(z+1)))
-    atanh z        =  log ((1+z) / sqrt (1-z*z))
+    atanh z        =  0.5 * log ((1.0+z) / (1.0-z))