From: Magnus Therning <magnus@therning.org>

On 24/08/10 03:47, John Millikin wrote:
[...]
> I would like to avoid hard-coding the error type to SomeException, because
> it forces libraries to use unsafe/unportable language features (dynamic
> typing and casting). However, given the apparent practical requirement that
> all iteratees have the same error type, it seems like there's no other
> choice.

I haven't worked enough with iteratees to have an informed opinion on this,
but I wonder what the pros and cons are of having an error state in the
iteratees at all.  In other words, why would this

 data Step a m b
     = Continue (Stream a -> Iteratee a m b)
     | Yield b (Stream a)
     | Error E.SomeException

be preferred over this

 data Step a m b
     = Continue (Stream a -> Iteratee a m b)
     | Yield b (Stream a)

(Maybe with the restriction that m is a MonadError.)