Larry mused:
> Alternatively, maybe there should be some way to express infinite sets.
> Not sure I like the idea of an infinite junction, but something resembling:
>
> subset PowersOf2 of Int where any(1,2,4...*)
> enum Perms of PowersOf2 <Read Write Exec>;
> say Exec; # 4
>
> Presumably the series in the junction would have to be sufficiently
> monotonic so we can know when we've looked far enough. Or we just
> allow something like one of:
>
> subset PowersOf2 is Set(1,2,4...*);
> constant PowersOf2 = Set(1,2,4...*);
>
> In any case, the idea is that an enum of something like PowersOf2 would
> be smart enough not to use values that aren't in the 'of' type.
I do like the idea of being able to specify the sequence of values of an
enumeration by using a series of some kind.
And I must say the one that feels most natural is the one that plays on
the equivalence of underlying equivalence of enums and constants, namely:
enum Perms <Read Write Exec Fold Spindle Mutilate> = 1,2,4...*;
This would also mean you could think of a "normal" enum:
enum Days <Sun Mon Tue Wed Thu Fri Sat>;
as simply defaulting to C< = 1...* >.
> We've got these silly series operators; it seems a shame not to use
> them for powers of two when appropriate.
I certainly agree there.
Damian
