[ tcl-Bugs-2010909 ] clock scan fails with %V

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Bugs item #2010909, was opened at 2008-07-04 21:54
Message generated for change (Comment added) made by ferrieux
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Category: 03. Timer Events
Group: current: 8.5.3
Status: Pending
Resolution: Invalid
Priority: 5
Private: No
Submitted By: haertel, ruediger (haertel)
Assigned to: Kevin B KENNY (kennykb)
Summary: clock scan fails with %V

Initial Comment:
The clock scan command returns always the current week when the given format only contains the week (%V).

test-case showing failure

for {set week 0} {$week < 22} {incr week} {
     set x [clock scan "$week 2008" -format "%V %Y"]
     puts [clock format $x]
}

However it works correctly when a week day is supplied.

test-case workaround

 for {set week 0} {$week < 22} {incr week} {
     set x [clock scan "$week Sun" -format "%V %A"]
     puts [clock format $x]
 
}


This could be a fix in the code. In that it assumes the current day.

Or this could be a fix in the documentation. In that it is clearly stated that for the scan and format %V the week day shall be supplied to.


>From my point of view I'd prefer a fix in the code. Primarily because clock already assumes in the workaround that the year is the current year.

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>Comment By: Alexandre Ferrieux (ferrieux)
Date: 2008-07-05 01:36

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Sorry, but I don't understand the reference to redundant groups: here we
are on the other end of the spectrum -- underspecified rather than
redundant. When we parse "2008 23" with "%Y %H" we get a similar situation,
but the result is compatible with all specified data, it is a date whose
time-of-day is 23:00 in year 2008. The same with %V violates the
compatibility rule since it gives noon today, and today is not in week 01.

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Comment By: Kevin B KENNY (kennykb)
Date: 2008-07-05 00:02

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A careful reading of clock.n (under SCANNING TIMES) shows that
[clock] here works as designed and documented.  I concede that
the behaviour of ignoring the 'week' format group in that case
is puzzling, but it fits with the fact that redundant groups
are (and must be) ignored in other cases - for instance,
in parsing an RFC2822 date, the day-of-the-week is presented
even though the other fields are sufficient to specify the date.

It is easy to parse a date like 2008-W27 if you need the
start of the week:

set date {2008-W27}
set secs [clock scan "$date-1" -format "%G-%V-%u"]

Another reason for the code to work the way it does is that
otherwise there is also a possibility of nonsense combinations
like "%G-%u" without a week number - either choosing a given
weekday in the first week, or a given weekday in the current
week number, would be surprising.



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