imprecise-exceptions.md

@@ -6,7 +6,12 @@ See [ExtensionDescriptionHowto](extension-description-howto) for information on
 ## Brief Explanation
 
 
-Exceptions may be thrown by pure code and caught in the `IO` monad.
+In Haskell 98, exceptions may be caught and thrown only in the `IO` monad.
+The `error` function generates failures from pure code, but cannot be caught.
+
+
+Imprecise exceptions may be thrown by pure code and caught in the `IO` monad.
+IO exceptions and `error` are subsumed as special cases.
 
 ## References
 
@@ -17,6 +22,7 @@ Exceptions may be thrown by pure code and caught in the `IO` monad.
 ## Pros
 
 - more robust programs
+- implemented by GHC and Hugs for several years
 
 ## Cons