On Saturday 23 December 2006 14:21, Stefan O'Rear wrote:
On Fri, Dec 22, 2006 at 08:05:08PM -0500, Steve Downey wrote:
Although terse, the subject really says it all. If i've a partial function, like a parser, what is considered good style for a library. The tradeoffs that I can see are that Maybe is a binary operation, while Error can communicate more information in the type of the error case. Is there some way to defer the error handling Monad to the calling context?
Your title answers the question. :)
All monads provide a "fail" operation, and any function that uses fail will be able to work with any monad's error handling mechanism.
Though this obviously forces you to encode your library's error information into a String, which is a serious limitation in my book. If your library is in an Error monad it seems straight forward for a consumer to get the fail behaviour, or even provide a wrapper in the library. Going the other way and having to decode Strings into richer error constructs may or may not be straight forward. I recall there has been previous (lengthy) discussion on errors and fail in this list. It might be worth having a trawl to get the different points of view. Daniel