On Sat, Jan 24, 2009 at 4:31 PM, Thomas Davie <[email protected]> wrote: > > On 24 Jan 2009, at 22:19, Henning Thielemann wrote: > >> >> On Sat, 24 Jan 2009, Thomas Davie wrote: >> >>> On 24 Jan 2009, at 21:31, Dan Doel wrote: >>> >>>> For integers, is _|_ equal to 0? 1? 2? ... >>> >>> Hypothetically (as it's already been pointed out that this is not the >>> case in Haskell), _|_ in the integers would not be known, until it became >>> more defined. I'm coming at this from the point of view that bottom would >>> contain all the information we could possibly know about a value while >>> still being the least value in the set. >>> >>> In such a scheme, bottom for Unit would be (), as we always know that the >>> value in that type is (); bottom for pairs would be (_|_, _|_), as all pairs >>> look like that (this incidentally would allow fmap and second to be equal on >>> pairs); bottom for integers would contain no information, etc. >> >> Zero- and one-constructor data types would then significantly differ from >> two- and more-constructor data types, wouldn't they? > > Yes, they would, but not in any way that's defined, or written in, the fact > that they have a nice property of being able to tell something about what > bottom looks like is rather nice actually.
It sounds like you're suggesting that all pattern matching on single-constructor data types should be irrefutable. In other words, "\(x,y) -> ..." would be equivalent to "\ ~(x,y) -> ...". I'm pretty sure this would cause problems if suddenly introduced in Haskell, but it might work in a new language. How would this work with seq? If (_|_,_|_) = _|_, does (_|_,_|_) `seq` () = _|_ ? -- Dave Menendez <[email protected]> <http://www.eyrie.org/~zednenem/> _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
