Very, very preliminary port of Chronos to Squeak published to SqueakMap
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Very, very preliminary port of Chronos to Squeak published to SqueakMap
 
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Avi Bryant is currently working on a port of Chronos to Squeak. He has published a Monticello package to SqueakMap that contains a very preliminary port. It is very much a "work in progress." When Avi is
satisfied that the port is sufficiently functional and stable, he will make a
general announcement to that effect. No promises have been made with
respect to when a version suitable for general use may become available, nor is
there any commitment to provide all the same functionality as is available from
the VisualWorks version. Of course, nothing prevents others from contributing
improvements/enhancements in addition to whatever Avi
publishes.
Initially, Avi
does not plan to port the Chronos Time Zone Compiler to Squeak. Tthe
Chronos Time Zone Compiler is used to generate the Chronos Time Zone
Repository from the information provided by the Olson Time Zone Database. Since
the Chronos Time
Zone Repository a) is available from the Chronos web site, and b) is usable "as is"
by any Smalltalk implementation (in fact, it would be usable by any programming
language, given a sufficiently powerful time zone implementation written in that
language,) that's not that big of an issue.
It's only recently
that I have become at all familiar with Avi's work. Initially, I only knew
he was one of the principal authors of Seaside. But
he's done much more than just that (although Seaside is impressive
enough by itself.)
I am very
appreciative of the contributution Avi is making towards porting Chronos to
Squeak.
Fair warning: As of Sat, 25 Feb 2006 03:31:56 +0000
(Universal Time,) the version on SqueakMap will not work "as is" in versions of
Squeak from 3.7 onward (you can load it, but if you execute the
initialization/installation "do it" that the pop-up Transcript window suggests,
you will then be unable to either save the image or compile any
methods.) The problem is caused by the fact
that the installation procedure (as implemented in the version currently
available from SqueakMap) redefines both DateAndTime and Duration so that they
are aliases for the Chronos classes Timepoint and ScientificDuration
(respectively,) in place of the native Chronology classes named DateAndTime and
Duration (and this issue is precisely why I chose not to use the names
"DateAndTime" and "Duration" as class names.) This problem can be
fixed if, before evaluating the
'ChronosEnvironment install' "do it" as suggested, the
following class method is first implemented:
ChronosSqueakEnvironment
class>>setProtectedGlobalVariables
ProtectedGlobalVariables := Set with: #ScaledDecimal with: #DateAndTime with: #Duration. Avi is using
Squeak 3.6 to do the porting work. The Chronology library did not become
part of standard Squeak until version 3.7, and so there is no issue raised by
(re)defining the globals DateAndTime and Duration as global aliases for
Timepoint and ScientificDuration (respectively) in versions of Squeak prior
to 3.7. That may well be why Avi is using Squeak 3.6 to do the port.
(Squeak badly needs a mechanism to more elegantly handle issues such as this
one.)
Note
that the version currently available
from SqueakMap has not been given the ability to access
files--so it can't retrieve
any time zones from the Chronos Time Zone Repository, and therefore Olson time zone keys such as
'Americal/Los_Angeles', 'Europe/Paris' and 'Asia/Tokyo' cannot be used to
identify a time zone. Nor is there
any code that makes any attempt to determine the local time zone from the
host operating system, nor any code that provides any locale
information.
Consequently, the
Chronos system time zone simply defaults to Universal Time (which is what the
native Chronology library does also, so at least you're no worse off than you
were before.) Nevertheless, you can still do quite a bit.
For example, after loading and properly initializing
Chronos, you can evaluate the following expression to set the Chronos system
time zone so that it matches the zone rules that have been in effect since 1996
for CET/CEST (Central European Time):
(ChronosTimezone
key: #'Europe/Berlin' name: #'Central European Time'
initialOffset: (ScientificDuration hours: 1) withAbbreviation:
#CET
until: (WeekOfMonthDayOfWeek month: 3 week: 0 dayOfWeek: 1) "The 'zeroeth week' means the last week of the month"
at: (TimeOfDay hour: 1 minute: 0 second: 0) relativity:
#universal
thenOffset:
(ScientificDuration hours: 2) withAbbreviation:
#CEST
until: (WeekOfMonthDayOfWeek month: 10 week: 0 dayOfWeek: 1)
at: (TimeOfDay hour: 1 minute: 0 second: 0) relativity:
#universal)
beSystem
Then, you can
evaluate "Timepoint now" to see the current time. And if you find
yourself in Madrid, Paris, Berlin or Amsterdam, the answer will even be
correct. However, due to the fact that the Squeak system clock reports
local time, setting the Chronos system time zone has no effect on what is
displayed when "Timepoint now" is evaluated. It only changes the results
of evaluating "Timepoint utNow." On a system whose clock reported
Universal Time, the situation would be reversed.
--Alan
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Re: Very, very preliminary port of Chronos to Squeak published to SqueakMap
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On Feb 24, 2006, at 10:09 PM, Alan Lovejoy wrote: > Avi Bryant is currently working on a port of Chronos to Squeak. He > has published a Monticello package to SqueakMap that contains a > very preliminary port. It is very much a "work in progress." When > Avi is satisfied that the port is sufficiently functional and > stable, he will make a general announcement to that effect. No > promises have been made with respect to when a version suitable for > general use may become available, nor is there any commitment to > provide all the same functionality as is available from the > VisualWorks version. Of course, nothing prevents others from > contributing improvements/enhancements in addition to whatever Avi > publishes. > Alan, thanks for the detailed post, it saves me from having to write one. Yes, for now I've only done a very preliminary port, but I do intend to keep working on it as time permits. It's actually quite a testament to how portably Chronos was written that as much works as it does given the small amount of effort and code that I put in. If anyone would like to help flesh the port out, let me know. Avi |
Re: Very, very preliminary port of Chronos to Squeak published to SqueakMap
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In reply to this post by Alan L. Lovejoy
On Fri, Feb 24, 2006 at 10:09:34PM -0800, Alan Lovejoy wrote:
> > Initially, Avi does not plan to port the Chronos Time Zone Compiler to > Squeak. Tthe Chronos Time Zone Compiler is used to generate the Chronos > Time Zone <http://www.chronos-st.org/downloads/time-zones.zip> Repository > from the information provided by the Olson Time Zone Database > <http://www.twinsun.com/tz/tz-link.htm> . Note that TimeZoneDatabase (on Squeak Map) provides a complete implementation of this in Squeak. Dave |
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