Use opaque type for Error

Author: paf31

README.md

@@ -4,7 +4,7 @@
 
 ### Types
 
-    type Error  = { stack :: String, message :: String }
+    data Error :: *
 
     data Exception :: !
 
@@ -13,4 +13,10 @@
 
     catchException :: forall a eff. (Error -> Eff eff a) -> Eff (err :: Exception | eff) a -> Eff eff a
 
+    error :: String -> Error
+
+    message :: Error -> String
+
+    stackTrace :: Error -> String
+
     throwException :: forall a eff. Error -> Eff (err :: Exception | eff) a

src/Control/Monad/Eff/Exception.purs

@@ -4,7 +4,22 @@ import Control.Monad.Eff
 
 foreign import data Exception :: !
 
-type Error = { message :: String, stack :: String }
+foreign import data Error :: *
+			    
+foreign import message 
+  "function message(e) {\
+  \  return e.message;\
+  \}" :: Error -> String
+  
+foreign import stackTrace
+  "function stack(e) {\
+  \  return e.stack;\
+  \}" :: Error -> String
+
+foreign import error
+  "function error(msg) {\
+  \  return new Error(msg);\
+  \}" :: String -> Error
 
 foreign import throwException 
   "function throwException(e) {\