Exceptions vs. Errors (Re: Readline read_history and write_history addition)

Isaac Dupree isaacdupree at charter.net
Thu Jan 24 13:56:06 EST 2008

>> It should really be:
>> block x = do
>>   IO blockAsyncExceptions#
>>   ret <- x
>>   IO unblockAsyncExceptions#
>>   return ret
>> in which case we could then supply implementations for
>> other monads as well.
> blockAsyncExceptions# has some tricks to restore tail-recursion in some 
> cases (see the paper).  But apart from losing that optimisation, I can't 
> think of any reasons why the above couldn't work - one thing you have to 
> worry about is what happens when x raises an exeption, but I think that 
> is handled by the way we save and restore the blocked state in catch.

what about if the monad is a transformed one with its own error handling 
methods (e.g. ErrorT IO) and so (IO blockAsyncExceptions#) is run but 
(IO unblockAsyncExceptions#) is not? Is that a problem?


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