On 01/20/2012 06:32 AM, Noel Power wrote:
Hi Andrew,
My primary concerns
1. Change in behavior that may break existing code.
the intent of the patch is to restore the previous behaviour ( by
previous behaviour I mean before integration of the feature that
erroneously removed the 'special' processing for '+' for dates ).
Additionally the intent of the patch is to make the behaviour for '-'
similar for'+' e.g. if Date + 1 gives a Date then surely Date - 1
should additionally give back at Date. Hopefully that makes sense :-)
So the intent was not original behavior, but the behavior that was
intended the first time but then left commented out. You then did one
better by allowing for subtraction. Now I know what you mean by "old
behavior". good.
2. Previous behavior was never flagged as an issue, and may arguably
be considered logical to some. for example, storing a "delta" in the
native type.
I don't think we should be afraid to change present behaviour if we
think it is wrong and especially if the impact is probably going to be
very minor ( as I think is the case here ). I would bet that the
behaviour we have at the moment is an incomplete attempt to behave in
a compatible way with vba. Where we can, I think if the cost is low we
should try to be compatible ( should actually look at what vba does
[*]). But... I take it that you are unhappy with changing the
treatment of '-' ? and wouldn't be in favour of the change right? (
funny somehow I thought in the previous mail thread that you were in
favour of even letting the Date type be set for all those numeric
operations, sorry I misunderstood you )
Oh no, I think that we need it on minus as well. I did state that your
change covered the majority case. My concern is that it may break
existing macros, which is how I found the bug in the first place. I
believe that your change will allow that particular macro to function
correctly. The macros that will break are macros that assume (date +/-
date) return date or that other operations such as * return date.
Logically, however, I do agree that (date - date) makes little sense as
a date and I have trouble envisioning the meaning of date * date.
I believe that your fix will allow date - date + date to return a date,
so in my brain, I expect it to work as I expect.
3. The rules are more complicated now and require complex examples to
explain; for example, time_1 + time_2 + time_3 returns a date but
time_1 + time_2 does not. We cannot simply state that math done with
dates or including a date returns a date.
yeah that doesn't sound right :-/ should remain a Date I would think
In a quick test under OOo, I did not test on LibO, I noticed that the
Time() function returned a different type than Now(). Oh, I see that
Time() returns a string. That explains a lot. A "real" time is (as I had
original thought) expressed as a Date that has a 0 integer portion.
I do believe, however, that all the original arguments for a Date are
the same for time. Logically, using time, 13:00 + 13:00 means nothing
that makes sense to me, so you still covered the majority case unless
someone chose to store elapsed time in a date object.
[*] table of behaviour in vba, pre the bug being introduced and post
patch
mso old behaviour present
--------------------------------
date + num Date Date Date
date - num Date Double Date
date * num Double Double Double
date / num Double Double Double
date + date Date Double Double [1]
date - date Double Double Double
date * date Double Double Double
[1] the date + date is clearly wrong (fixing that would address '3.'
above. )
personally I am all for fixing this to be compatible
The only thing with which I disagree is that I would have addition and
subtraction return the same types. So, I would say that if date + date
returns a date (as your chart shows for MSO) then I would have date -
date return a date as well. If not, then I would leave your original
change as is so that they are consistent for addition and subtraction.
What type is "-date"? I see that never returned a date so (date +
(-date)) will return a date.
--
Andrew Pitonyak
My Macro Document: http://www.pitonyak.org/AndrewMacro.odt
Info: http://www.pitonyak.org/oo.php
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