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davorg (18)

davorg
  dave@dave.org.uk
http://dave.org.uk/
Yahoo! ID: daveorguk (Add User, Send Message)

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Journal of davorg (18)

Sunday December 29, 2002
02:57 PM

Time::Period

[ #9663 ]

I've been dabbling with overload.pm over the last week or so. I've never really looked at it in much depth before, but I'm scheduled to give a talk on to london.pm next month and that's always a good excuse to learn something new.

I was looking for a good (but slightly unusual) example for the constant overloading feature of overload.pm when I came up with the concept of Time::Period.

Basically, it allows you to do date calculations in a pretty easy to understand way. You can simply do something like this:

use Time::Period ':constants';

$one_month = '1m';
$now = time;
$then = $now + $one_month;
print scalar localtime $then;

Of course you can make that simpler with code like:

$wake = time + '1y + 1d'; # a year and a day
print "The princess will wake up at ",
  scalar localtime $wake;

It's on its way to CPAN, but in the meantime you can get it from http://dave.org.uk/modules/.

Oh, and if Trelane is reading... that's the topic for my talk at the next tech meet.

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  • Check out Time::Piece, which ships with Time::Seconds. Also check out Date::ICal, which ships with Date::ICal::Duration.

    All achieve the same thing.
    • I seem to recall that both Date::Calc and Date::Manip might also do the same thing. Could be wrong though as it's been a while since I've looked...
    • Oh, I know about Time::Seconds (I'm a big advocate of using Time::Piece). This isn't my attempt to replace it, just something that I was playing around with that I thought I'd share.

      There are differences between the two module tho'. Time::Seconds uses exported symbolic constansts where Time::Period uses objects. Also adding one year or one month to a date using Time::Seconds will add a fixed number of seconds whereas Time::Period will really add one year or one month.

      Didn't know about Date::ICal::Durati

      • Yep, this is a rather fundamental flaw in Time::Seconds (though there will always be issues with adding real durations too - like what to do adding a month at March 31st). I have been thinking seriously about re-writing Time::Piece entirely in terms of Date::ICal to try and fix this flaw.
  • Is that one month, or one minute?
    • Yeah, it's really unhelpful that "month" and "minute" both beign with "m" :(

      To get round that I arbitrarily decided that lower case letters represent units of time that are a day or bigger and uppercase letters represent untis of time that are smaller than a day. Another way of putting it is that lower case letters represent dates and upper case letters represent times.

      So '1m' is one month. '1M' is one minute.

  • Cool, now I don't have to chase you about what you're talking about, only how long.

    Niggles on the module:

    • print Time::Period->new("1y") - Time::Period->new("1S") returns "1y, 1S" which is obviously wrong.
    • print Time::Duration->new("24H")*2 does not DWIM, it complains about *, but I see that's on your TODO
    • I can't understand what the codes doing very well, you've not written a single comment ;-)
    • Cool, now I don't have to chase you about what you're talking about, only how long.

      Can I have half an hour?

      • print Time::Period->new("1y") - Time::Period->new("1S") returns "1y, 1S" which is obviously wrong.
      • print Time::Duration->new("24H")*2 does not DWIM, it complains about *, but I see that's on your TODO

      Addition is the only operation that is currently documented. Therefore it's the only one you should expect to work as documented :)

      • I can't understand what the codes doing very well,