simonmar at microsoft.com
Tue Jan 25 09:24:39 EST 2005
On 22 January 2005 07:14, Ashley Yakeley wrote:
> There's been a lot of discussion here and other lists of replacing
> System.Time, and indeed Simon M. is working on a replacement proposal:
> Rather than talk about specific Haskell code, I'd like to discuss the
> measurement of time in general, how these concepts might be expressed
> in Haskell, and what people might want from a time library. Rather
> than propose anything, I want to try to ask some of the right
I'd like to join the others in saying thanks for a fine summary, Ashley.
On the subject of the NewTime library you mentioned, it was the
culmination of a long thread (or threads) on this list a while ago. I
think it's a pretty good stab at an API for manipulating and converting
- absolute time (TAI)
- times in calendar representation
but it is missing
- time offsets (eg. "1 day later")
- a more complete/accurate timezone table
- some way to update the leap second table
- geographical time zones
and probably some other things.
my plan was that the whole "time offset" issue would be a layer on top
of this library, as others have suggested. You can already do simple
calculations using CalendarTime.
The representation of absolute time could be revisited.
What I mean by "geographical time zones" is some notion of a time zone
that is independent of daylight savings time. The current TimeZone type
is a fixed UTC offset (which I think is right), but there's no way to
say "what's the local time in London at time T?".
I probably won't be doing much to this library, but I think it's a good
starting point for anyone who wants to explore further.
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