I don't currently have anything to add to this discussion, but I want to
encourage you all to keep having it because I think it has potential to
improve the language in the "do things right or don't do them at all"
philosophy that Haskell tends towards.
-- ryan
On Fri, Jan 20, 2012 at 6:32 AM, Jacques Carette
On 19/01/2012 10:19 PM, Edward Z. Yang wrote:
In other words, MonadZero has no place in dealing with pattern match failure!
I completely agree. See "Bimonadic semantics for basic pattern matching calculi" [1] for an exploration of just that. In the language of that paper, the issue is that there is a monad of effects for actions, and a monad of effects for pattern matching, and while these are very lightly related, they really are quite different. By varying both monads, one can easily vary through a lot of different behaviour for pattern-matching as found in the literature.
I should add that if we had known about some of the deeper structures of pattern matching (as in Krishnaswami's Focusing on Pattern Matching [2], published 3 years *later*), we could have simplified our work.
Jacques
[1] http://www.cas.mcmaster.ca/~**kahl/Publications/Conf/Kahl-** Carette-Ji-2006a.htmlhttp://www.cas.mcmaster.ca/%7Ekahl/Publications/Conf/Kahl-Carette-Ji-2006a.h... [2] http://www.cs.cmu.edu/~neelk/**pattern-popl09.pdfhttp://www.cs.cmu.edu/%7Eneelk/pattern-popl09.pdf
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