Re: [office] Excel 2007 != Ecma spec YEARFRAC. Not even slightly. Whatshould we do?

From a storage perspective,  is
there any backwards compatibility problem caused by moving from our current
integer bases to strings, where five of the strings are "0",
"1", "2", "3" and "4" ?

If we did that we could add others like
"NYSE_X25", "ISDA_Rule25" or whatever.

-Rob

"David A. Wheeler" <>
wrote on 04/18/2008 02:56:31 PM:

> In general, the formula specification tries to follow EXISTING

> conventions wherever reasonable.  _All_ spreadsheet implementations

> use integer "basis" values for all their functions that
have

> such a parameter.  I agree that using a string has its merits,

> but using an integer is reasonable enough.

> In fact, integers make it easy to create "ranges", and would

> actually _ease_ transitions if there are differing interpretations

> of basis values.

> 

> I think we should try to AVOID spec'ing something incompatible

> with all existing implementations unless we have a pressing

> need to do so, and I don't think this is compelling.  That said...

> 

> 

> > On Fri, Apr 18, 2008 at 7:00 AM, David A. Wheeler 

> <> wrote:

> > >  The problem is that basis values need not be a constant
in the 

> cell; it might be

> > >  from another cell and/or a calculation (directly or
indirectly), e.g.:

> > >  YEARFRAC([.A5];[.B5];[.C5]+1)

>  

> Warren Turkal:

> > This seems like an unrealistic use case. In all sincerity, why
would

> > someone do that? Is it common? I just don't see folks selecting
the

> > basis by saying I want whatever the basis is identified by taking
the

> > identifier of some basis (e.g. actual/actual) and adding 1 to
it.

> 

> You're right, that was a silly example.

> 

> But a more realistic one is:

> 

>  YEARFRAC([.A5];[.B5]; IF(CONVENTION="US"; 0; 4))

> 

> Now the filter has to start digging through the expression tree,

> or end up with a complicated resulting expression.  Ugh.

> 

> > Having said that. If people do it, import filters can just map
it to

> > whatever fixed string it's value corresponds to on import...

> 

> Yes, import filters can fix it... but let's try to make it easy on

> the filters!

> Simple implementation is very important for getting a spec implemented.

> 

> Switching from an integer to a string representation does NOT

> really ease the "different basis interpretation" problem
at all.

> It just means that EVERYONE has to convert, instead of only

> SOME people having to convert.  That makes things worse, not
better.

> Integers also tend to be more efficient, and make it easy to

> do conversions of whole groups (e.g., we could make the

> Excel 2007 and OOXML conventions differ by 128, and then

> adding/subtracting 128).

> 

> Since everyone uses integers NOW for basis values, let's try to stick

> with that if it's practical to do so.  And I think it is.

> 

> --- David A. Wheeler

> 

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