On Tue, Jan 02, 2007 at 09:24:20AM -0800, Larry Wall wrote: : But I'm also still wondering whether a simpler approach is to declare : that Num is a role that can encapsulate objects of class Int, Num, : Rat, or Dec as necessary. There also a lot to be said for simple...
Well, that's wrong several ways. It would be more like Num is a Scalar that is constrained to a Numeric role. But Scalars are mutable, and that plays havoc with the value semantics. How can you tell if two different numeric types are really holding the same value? There's no one-to-one correspondence between approximate types and exact types. You can pretend that a floater is a single value, but a given floater really represents a range of rational and irrational values. You'd really like Num to at least pretend it has value semantics though... :/ Larry
