On 01/12/12 16:58, Magicloud Magiclouds wrote:
Yes, that is a problem. But consider my PS in original mail, I have no idea what exception should I catch. Where could I get that information?
In my experience, exceptions fall into three categories. First, when performing IO, some functions throw an exception instead of returning an error code, as is the case for many of the functions in System.IO; however, in these cases the exceptions that can be thrown are clearly documented. Second, when a bug in your code has caused it to reach a point where it can no longer proceed, such as when there is a deadlock, when there is an infinite loop, when you violated a precondition of a pure function by for example calling "head" on an empty list, etc.; in such cases it is very unlikely that you would even want to catch and gracefully recover from them, so an exception specification would not help you very much anyway. Third, when you are running someone else's code and you want to be able to catch any exceptions it throws so that you can handle the error reporting yourself; in this case the only thing that you care about is whether the exception is an AsyncException or not, since if it is an AsyncException then you should almost certainly should just let it propagate up the call stack rather than dealing with it yourself. Incidentally, in all of these cases catching *all* exceptions is a bad idea unless you really know what you are doing for the reasons that others here have pointed out, so I apologize for misleading you with that suggestion. Cheers, Greg