The app I’am working on, converts a jsonString to another string encoding.

The function I want to write is  jsonString -> (encoding, errorMsg)  so String-> (String, String)

For this purpose I have a typeable datastructure Glass. Because it is typeable I can do (decodeJSON jsonString) :: Glass

But sometimes the jsonString is not valid (misformed or wrong fields). decodeJSON then throws a exception.  I want to

catch that exection and transform the result to something like (“” , theErrorMsg). Unfortunately all catch functions want IO parameters.

What can I do?

Kees