Re: How do I create dynamic exceptions

22 Jul 2003


      On Tue, 22 Jul 2003 12:51:24 +0100
"Bayley, Alistair"  wrote:
...
Exceptions, again...
The docs for Control.Exception say (for Dynamic exceptions): "When
using dynamic exceptions it is advisable to define a new datatype to
use for your exception type, to avoid possible clashes with dynamic
exceptions used in other libraries."
So I went with that and created a datatype for my exceptions:
...
data MyException = MkExc Int String
... but now it seems I have to install this as an instance of
Typeable, and I don't see how to do that.
...
instance Typeable MyException where
  typeOf ? = ?
The documentation for Data.Dynamic is pretty clear for this and I
believe with GHC6 you can derive Typeable.

{-# NOINLINE myExceptionTyCon #-}
-- the documentation suggests a fully qualified name
myExceptionTyCon = mkTyCon "MyException" 

instance Typeable MyException where
    typeOf _ = mkAppTy myExceptionTyCon []

Re: How do I create dynamic exceptions

Derek Elkins