Re: Excel Math Bug

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From: Tom Ogilvy (twogilvy_at_msn.com)
Date: 08/03/04 

Date: Mon, 2 Aug 2004 23:38:20 -0400

the unary negation operator is not the same as subtraction. A basic flaw
in your argument.

Your mnenonic is incomplete. How would you express a negative number in
an equation?

the second flaw is that you attribute the syntax used in writing formulas in
Excel to be synonymous to hand written formulas. But it isn't - it is a
syntax defined by the authors of Excel. Excel defines a set of rules for
its syntax which, to increase comfort, to a large extent parallels hand
written formulas, but nonetheless, it is a syntax defined by the creators of
excel. It is thus incumbent on the user to understand that syntax; not make
assumptions. 

-- 
Regards,
Tom Ogilvy
"fred" <fred@fred.frd> wrote in message
news:iuzPc.108286$fv.98008@fe2.columbus.rr.com...
> Well, yes, that is basically the same thing a couple of my friends said.
> But none of them are mathematicians.  The only thing about it is that
that's
> not how math/algebra/calculus/etc. is done.  Negation and subtraction are
> one-in-the-same to the best of my somewhat-in-depth knowledge.  There's
even
> the mnemonic device "Please Excuse My Dear Aunt Sally" to help remember
the
> order in which operations are supposed to be executed (Parenthesis,
> Exponents, Multipication, Division, Addition, Subtraction).
>
> To me the only valid argument, based on different priorities, is that
> non-math-people, when using actual numbers, not cell references, expected
> =-5^2 to be "negative five, squared".  And they wanted to satisfy the
> secretaries and bean counters, not the heavy-duty math people.
>
> However, having done software development myself, I think it most likely
> that it's just a bug and just hasn't been fixed yet.   In fact, to me,
> putting in a zero and getting a different answer proves it's wrong.
>
>
> "Alan" <alan@alan.alan> wrote in message
> news:%23t8ZNuNeEHA.724@TK2MSFTNGP10.phx.gbl...
> > "fred" <fred@fred.frd> wrote in message
> > news:OJxPc.108250$fv.101850@fe2.columbus.rr.com...
> >
> > >
> > > Are they rewriting math rules now? ... negation is different from
> > > subtracting?  Indeed!  Not in any math book I've ever seen.
> > >
> >
> > This is an interesting point.
> >
> > I guess I tend to view the two things as being separate and different
> > in nature.
> >
> > Negation (in the sense that I believe you are using it above) such as
> > turning +5 into -5 'creates' a new number.  The value of that number
> > is -5.
> >
> > Subtraction is an operation performed on one value with another.
> > Therefore, subtracting +5 from a value is a different thing.
> >
> > I guess where this becomes important is in the example used elsewhere
> > in this thread of:
> >
> > =-5^2
> >
> > It could be argued that it is quite valid for either answer (+25
> > or -25) to be correct depending on whether we are squaring -5 or
> > whether we are (implicitly) subtracting 5^2 from (the implicit) 0 that
> > is not shown.
> >
> > If we put the zero in:
> >
> > =0-5^2
> >
> > then I would suggest that the *only* valid interpretation is that we
> > are subtracting 5^2 from zero, and thus the answer *must* be -25.
> >
> > Given that excel must have rules, it does not seem unreasonable for
> > the algorithms to require an explicit subtraction, else go with the
> > interpretation that we are squaring -5.
> >
> >
> > Having said all of that, if we don't bother to use brackets to make
> > the calculations completely explicit and unambiguous, then I guess we
> > are each *choosing* to take the risk - whether we know it or not.
> >
> > Does my thinking sound reasonable?
> >
> >
> > Alan.
> >
> >
> >
> >
>
>

Relevant Pages

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