On Thu, 19 Feb 2009, Larry Wall wrote:
Is there a way in which a class which does the Date role could change the
type $.year so it was "Int|Undef"?
Doesn't have to. Int already comes with an undefined value known as
Int, aka the protoobject. Only subset types (and their cousins, native
types) can restrict values to being defined, and they do so on the
primarily on basis of constraints, and only secondarily on whether the
underlying storage can represent an undefined value. So an Int can be
undefined, but an int can't. A Num can be undefined, but a num can only
approximate that with NaN.
Well, if you look at the spec I _did_ create subsets for most of those
values like this:
my subset Hour of Int where { 0 <= $^a <= 23 };
That being said, I'm thinking that all actual times represented by
floats in Perl are TAI time, not the Unix pseudo time with hidden
leap seconds. I sure wish they'd done away with civic leap seconds
in 2000 and said we'll put in a leap minute or two on century breaks...
That's certainly fine with me, but I think we'd still want some simple
objects on top of them, rather than handing people a single epoch numbre
to deal with.
-dave
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