help asked for Calc jump function with empty arguments

[Eike Rathke]

Hi Winfried,

On Thursday, 2015-02-05 12:44:56 +0100, Winfried Donkers wrote:

> >> and =IFERROR(1/0;) returns an empty cell, not an error message.
> 
> >This is correct and voids my earlier proposal to propagate the ocMissing token through in the final result. Actually we need to pop an ocMissing and push an ScEmptyCellToken in such case.
> 
> (To make it clear for me, =IFERROR(1/0,) results in an empty cell in Excel and an error in Calc.)
> Popping ocMissing seems a bit of a problem - for me ;-) - as ScInterpreter::Interpret calls ScIfError() first and then changes opcode. So, when I detect ocMissing, I don't know from which function.
> In the case of IFERROR I could use a boolean to return an empty cell, but in the case of IF I need to know the result of the expression in the first argument or whether the ocMissing refers to the ifTrue argument or the ifFalse argument.
> I hope you understand my problem.

Yup.. actually the pop/push approach would only work as final result,
not in between on the fly.. So, I tried things in Excel and all these
yield TRUE, meaning that the "empty cell" is preserved as code path:
=IFERROR(1/0,)=""
=IFERROR(1/0,)=0
=IF(1,,)=""
=IF(1,,)=0

We have something similar with formula::svEmptyCell, my rough guess now
is it should be enough to treat svMissing the same as svEmptyCell in
comparisons (ScInterpreter::Compare() and ScInterpreter::CompareMat()),
instead of forcing it into a context of svDouble at that stage, and when
preparing the final result check for an ocMissing (interpr4.cxx line
4371 in Interpret() at "obtain result" before the current if(
pCur->GetOpCode() == ocPush )) and if so pop it and push an empty cell,
i.e. Pop(), PushTempToken( new ScEmptyCellToken( false, false))

Does that clarify?

  Eike

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