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</o:shapelayout></xml><![endif]--></head><body lang=NL link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>The app I’am working on, converts a jsonString to another string encoding. <o:p></o:p></p><p class=MsoNormal>The function I want to write is jsonString -> (encoding, errorMsg) so String-> (String, String) <o:p></o:p></p><p class=MsoNormal>For this purpose I have a typeable datastructure Glass. Because it is typeable I can do (decodeJSON jsonString) :: Glass<o:p></o:p></p><p class=MsoNormal>But sometimes the jsonString is not valid (misformed or wrong fields). decodeJSON then throws a exception. I want to<o:p></o:p></p><p class=MsoNormal>catch that exection and transform the result to something like (“” , theErrorMsg). Unfortunately all catch functions want IO parameters. <o:p></o:p></p><p class=MsoNormal>What can I do?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Kees<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>