Darren Duncan wrote on 2009 Feb 17:
Timothy S. Nelson wrote:
Agreed, and that's kinda what I'm doing. But I still think
there's room for improvement. I'll try and design an API that does
what DateTime does, but:
Talking about dates and times, I have some suggestions.
Second of all, I think a more generic term than DateTime should be used
to name an object that represents an instant in time; for example I
suggest calling it "Instant". The name "Instant" fits in a lot better
in the company of other generic sounding temporal data types like
"Duration" etc. Then, you can say that things like DateTime, Date,
Time, etc are subtypes of Instant.
See also
http://search.cpan.org/dist/Muldis-D/lib/Muldis/D/Ext/Temporal.pod where
I've specced out such matters, and that illustrates something I
recommend for you. My Instant types very closely resemble both the Perl
DateTime library as well as the SQL temporal types, which are actually
very similar, though I've generalized it a bit. This spec explicitly
does not support time zones (it has UTC or floating, that's it) and it
doesn't include conversions with strings, but it has the foundation on
which such could be built. And yours doesn't have to be the same of
course.
As a follow-up to my initial 2009 Feb 17 post that first suggested the name
"Instant" and cited my Muldis D language as a specced example ...
I'll start off by saying that the evolving design of Muldis D in general seeks a
happy medium between the evolving design of Perl 6 and the established design of
SQL, while being guided especially by The Third Manifesto's abstract concept of
a "D" language. Over time, a significant portion of the input I've been making
into the design of Perl 6 has been based on my prior work hashing out the same
ideas in Muldis D, and similarly, ideas hashed out for Perl 6 have been
attracting me to continue changing Muldis D to more closely resemble Perl 6.
It's the whirlpool attractor development model but on a multi-language scale.
And so, if anyone is interested in this tangent, I just released Muldis D
version 0.60.0 on CPAN, whose feature change is an evolution of the language's
temporal types and operators. The types named 'Instant' and 'Duration' now are
in the language core rather than an optional extension, and are defined to mean
exactly what the same-named types of Perl 6 do (see S02), a point on the TAI
timeline measured in seconds, and a difference between 2 of those. I also kept
my prior meanings, defined in terms of YMDHIS, as disjoint types UTCInstant and
UTCDuration etc, in a language extension which would correspond to a CPAN module
like DateTime. The TAI seconds and UTC YMDHIS are kept as disjoint types rather
than being representations for the same types because there is no fixed rate of
conversion between the two representations in general, with UTC leap seconds of
the future being unknown; instead there are mapping functions that people can
use between the types, that apply what we known sans future leap seconds, and so
aren't expected to be consistent over time. The most relevant 2 files in the
spec for this change are
http://search.cpan.org/dist/Muldis-D/lib/Muldis/D/Core/Types.pod and
http://search.cpan.org/dist/Muldis-D/lib/Muldis/D/Ext/Temporal.pod . So at this
point, practically every Muldis D core type directly maps to a Perl 6 core type,
and in most cases the types have the same names and semantics.
-- Darren Duncan
