It's not released yet, but persistent 0.2 is going to be using enumerator. I personally don't mind SomeException as a hard-coded error type, but go ahead and do whatever you think is best for the API.
Michael On Tue, Aug 24, 2010 at 5:47 AM, John Millikin <jmilli...@gmail.com> wrote: > After fielding some more questions regarding error handling, it turns > out that my earlier mail was in error (hah) -- error handling is much > more complicated than I thought. > > When I gave each iteratee its own error type, I was expecting that > each pipeline would have only one or two sources of errors -- for > example. a parser, or a file reader. However, in reality, it's likely > that every single element in a pipeline can produce an error. For > example, in a JSON/XML/etc reformatter (enumFile, parseEvents, > formatEvents, iterFile), errors could be SomeException, ParseError, or > FormatError. > > Futhermore, while it's easy to change an iteratee's error type with > just (e1 -> e2), changing an enumerator or enumeratee *also* requires > (e2 -> e1). In other words, to avoid loss of error information, the > two types have to be basically the same thing anyway. > > 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. > > So, my questions: > > 1. Has anybody here successfully created / used / heard of an iteratee > implementation with independent error types? > 2. Do alternative Haskell implementations (JHC, UHC, Hugs, etc) > support DeriveDataTypeable? If not, is there any more portable way to > define exceptions? > 3. Has anybody actually written any libraries which use the existing > "enumerator" error handling API? I don't mind rewriting my own > uploads, since this whole mess is my own damn fault, but I don't want > to inconvenience anybody else. > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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