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Hi Noel,

On Monday, 2012-01-16 16:11:14 +0000, Noel Power wrote:

Not every operation on date types should return a date,
I have to admit I was swayed by Andrew's point that letting the
operations just return Dates seems more consistent.Also it would
seem to me subtraction should at least mirror the behaviour of
addition.

e.g.
    something = date() + 1 ' something becomes a variant date ( 1
day into the future )
    something = date() - 1 ' something becomes a variant date ( 1
day in the past ) ( Note: previously this would just be a strange
double value e.g the numeric rep of the date type )

Yes, these are fine as dates.

Although I don't really see the point of exponential or division
etc. operations on dates, keeping the type didn't seem like it would
cause any problems ( and simplified the code )

However, given previous bad experiences with basic with seemingly
minor changes in combination with your query I am getting nervous
:-/
i.e. substracting two dates should return a number of days (I
don't think adding/multiplying/dividing two dates makes sense, but
it should return a number of days as well).
hmm  Date 'operation' Date puts a different spin on things :-/

with the change on master

dim tomorrow as Date
dim yesterday as Date

tomorrow = date() + 1
yesterday = date() - 1
result = tomorrow - yesterday ' previously would have given 2 as a
result with a type variant/double but now gives a strange date (
result of trying to convert 2 into a date )

and of course... that's not good :-(

However I'd still like to see macro code like

   something = date() - 1

return a date just like the addition case

Of course.

We have a number of choices

a) safest, just restore the old code
b) not so risky ( I think ), and... would change the present
behaviour in consistent way for treatment of minus operator
-                    if( GetType() == SbxDATE || rOp.GetType() == SbxDATE )
+                    if( ( eOp == SbxPLUS || eOp == SbxMINUS ) && (
( GetType() == SbxDATE || rOp.GetType() == SbxDATE ) && ( GetType()
!= rOp.GetType() ) ) )

That one (b) looks good.

c) risker variant of b that allows all operations on a date type to
retain it's date type

-                    if( GetType() == SbxDATE || rOp.GetType() == SbxDATE )
+                    if( ( GetType() == SbxDATE || rOp.GetType() ==
SbxDATE ) && ( GetType() != rOp.GetType() ) )

I don't spot sense in 2*today() => 2124-02-02  ;-)

  Eike

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