Larry Wall wrote:
<snip>
This still seems to be confusing implementation issues with the point
I'm trying to make about the basic nature of time.
Duration and Instant are both simple (but typed) Num semantics
on seconds. There are no integers unless you specifically ask for
an interpretation in minutes, hours, fortnights, what have you.
The basic flow of time is continuous and stable in Perl 6, or as
continuous and stable as we can make it.
<snip>
I couldn't agree more with this, and that's certainly how we want to look at
things as a generic conceptual or practical foundation.
I also take back my stated preference of the internal format being in terms of
YMDHIS due to stored future date values continuing to DWIM over time.
I now think that a simple Num that counts seconds from some rigorously defined
epoch, and I mean rigorous with the kind of rigor that the duration of a second
is currently defined in terms of a cesium-133 atom at a particular temperature
within gravity of a particular strength; for that matter, Perl 6 should
explicitly define what a second is as well, though it can and probably should
just punt and refer to "what it says in <the particular official standards
document>".
And so, to deal with my concern about DWIM, what we probably want is some other
data type that represents a lazy conversion to the internal type from whatever
interpretation the user wants; that is, the alternate type would, eg, use YMDHIS
internally, which is stored for persistence, so to DWIM for the user. And this
alternative can be punted to the domain of CPAN modules.
In contrast, the simple Num-from-rigorous-epoch approach works when you want to
deal with current-time, time-stamps, stopwatches, any kind of serious math or
physics etc, where it is really the relative time of events relative to each
other that is important, and not where they fit on a human calendar.
Only atomic time in atomic seconds will be futureproof over the long
haul. All other interpretations are negotiable via libraries, but
time must be considered a position on a real timeline, and seconds
are a reasonable unit for measuring that timeline. The method in
$duration.seconds should not have to do any calculations to return
the Num number of seconds, because whether we're talking about
gigaseconds or femtoseconds, we're still talking about seconds.
Time has no relationship to integers apart from cultural artifacts.
Let's keep our integers in the libraries, not in the fundamental
definition of what "now" and "then" mean.
Yep, couldn't agree more.
-- Darren Duncan
