On Tue, 2011-09-20 at 15:28 -0400, Casey McCann wrote:
I actually think the brokenness of Ord for floating point values is worse in many ways, as demonstrated by the ability to insert a value into a Data.Set.Set and have other values "disappear" from the set as a result.
Definitely Ord is worse. I'd very much like to see the Ord instance for Float and Double abandon the IEEE semantics and just put "NaN" somewhere in there -- doesn't matter where -- and provide new functions for the IEEE semantics. As for Enum, if someone were to want a type class to represent an enumeration of all the values of a type, then such a thing is reasonable to want. Maybe you can even reasonably wish it were called Enum. But it would be the *wrong* thing to use as a desugaring for list range notation. List ranges are very unlikely to be useful or even meaningful for most such enumerations (what is [ Red, Green .. LightPurple]?); and conversely, as we've seen in this thread, list ranges *are* useful in situations where they are not a suitable way of enumerating all values of a type. -- Chris