Known bug in Excel????

[mortgageman]

According to math rules 2^3^2 should equal 2^9 (you go right to left in this case). Excel gives 64. Is this a known bug?

Gene Klein

 

[Kenneth Hobson]

The link that I posted did address exponents which is what Excel does:

Rule 2: Simplify all exponents, working from left to right.

For my example where I gave a scenario about the moon shot, imagine someone using an older Excel file or other programming language, developed before the "bug" was fixed, the computations would be incorrect.

I don't think that any programmer is going to change their program's order of precedence to match math rules.

I guess if you think that it is a bug, you should report that in a beta testing round. Other beta testers would have to agree before Microsoft would consider it if my past experience is any guide.

 

[xenou]

According to math rules 2^3^2 should equal 2^9 (you go right to left in this case). Excel gives 64. Is this a known bug?

It's an interesting question. Is 2^3^2 a form of notation used in (say) math textbooks - which is to say, is it written this way by humans? I would normally write it the way Norie showed, and would also understand that to "transpose" this into an Excel formula, I would have to write it as 2^(3^2).

Pursuant to other comments, I lean towards having one clear and simple rule (operands are evaluated left to right when they are the same), than to have exceptions that would need to be memorized (except when the operand is exponentiation). This is an adjustment we make to to adapt our formula notation in view of the situation of doing mathematics on a computer - probably, ultimately, to simplify data entry on a keyboard, since there's no easy way to type math formulas as they appear on paper.

 

[Norie]

Perhaps it's top to bottom with exponentials.

 

[mikerickson]

I think that it's good practice to use parenthesis.
Rules of precidence and order of operation are OK to know, but are akin to using defaults all the time.

Just as rngData.Offset(23) is less clear than rngData.Offset(23, 0),

2^3^4 is less clear than 2^(3^4)

 

[tweedle]

perhaps so Norie...

http://en.wikipedia.org/wiki/Exponentiation#Identities_and_properties

(parenthetics are a good thing)
I can't recall a specific instance of my institutional days, but I'm pretty sure I never would have gotten away without explicitly declaring parenthetics, in Alg., Calc., Programming or Lit.

 

[Norie]

I think it's very good practice to use parentheses.

PS Can we have a discussion about how to use/spell <S>parethisis</S> <S>parantheses</S> parentheses?

 

[Scott Huish]

parenthesis is singular
parentheses is plural

 

[Kenneth Hobson]

When I first looked at this thread, I too looked at Tweedle's referenced link. Here is another with an example for Calculators. http://www.answers.com/topic/order-of-operations

My HP48SX and TI-36SX compute 2^2^3 as 64 as well. Howsoever, my HP48SX also has an Equation function that shows the equation as Norie noted and returns 512.

Of course if we could write formulas in mathematical equation format in Excel as Norie did, we would have a better understanding and write the proper equation for Excel now that we all know Excel's order of operation.

 

[mikerickson]

How to spell parenthesis? I use a Spell checquer.

 

[mortgageman]

In that example, Excel is NOT doing it's calculations Right To Left...
Instead, it is doing Multipliction Before Addition..

The same result would occur if it was writtin:
=4x2+3

Multiplication and Devision come before addition and subtraction..

No disagreement here on what you have said. The order of operations is - with one exception - left to right WITHIN operators that have the same precedence. In your example, Multiplication has a higher (i.e. not the same) precedence then addition. The one exception is my topic here a power to a power. The order of operations for this says right to left.

Gene Klein