RE: df#50950 sort out Calc (ISO)WEEKNUM functions

Hi Eike,


> I'm a bit lost here. Maybe we need to sort that out from scratch again.
> This appears to be the most complicated change in function names we're
> tackling because of the different functions AND having an Add-In function
> involved AND different names for similar but not quite identical functions
> in UI and file formats.
>
> Let's postpone until April ...

It's April, the sun is up :)

I'll try to explain the situation as I see it.

As you know, the problem is that the ODFF function name ISOWEEKNUM is currently used for a function 
with WEEKNUM functionality.

I checked the function definitions for WEEKNUM and ISOWEEKNUM, for ODFF and Excel. ODFF and Excel 
are as good as identical, except that Excel may experience problems when the date value is entered 
is text.
I intend to ignore that difference and support both WEEKNUM and ISOWEEKNUM in Calc.

I propose to put right in 2 steps.
UI:                     English function name used in user interface
ODFF:           function name used in ODFF-document (ods)
ODFF-legacy:    function name that can be read from ODFF-document and will be converted to ODFF 
function name; used for backwards compatibility (conversion in ScCompiler::IsOpCode())
EXcel:          function name used for export/import to/from Excel (xlsx)

LO version 4.5:
UI              ODFF                    ODFF-'legacy'           Excel
WEEKNUM WEEKNUM         ISOWEEKNUM                      WEEKNUM
ISOWEEKNUM      ISOWEEKNUM_TMP                                  ISOWEEKNUM
remove UI WEEKNUM_ADD (similar as with GCD_ADD, gerrit#15185)

LO version 4.6:
UI              ODFF                    ODFF-'legacy'           Excel
WEEKNUM WEEKNUM                                         WEEKNUM
ISOWEEKNUM      ISOWEEKNUM              ISOWEEKNUM_TMP          ISOWEEKNUM

Any questions, objections, suggestions?

Winfried