[R] Spreadsheet math problem (exponentiation)

[John McKown]

On Fri, Sep 18, 2015 at 10:04 AM, David L Carlson <dcarlson at tamu.edu> wrote:

> Unfortunately the order of operations is not universal in computing. The
> real question is whether a program performs the way it is documented. Excel
> documents that unary operations take precedence over exponentiation and
> that within groups, the order is left to right. LibreOffice Calc behaves as
> Excel, but does not document the order of operations except to say */
> before +-, left to right. I couldn't find any statement about the order of
> operations in the documentation for Gnumeric.
>
> R documents that unary operations come after exponentiation and, within
> exponentiation, the order is right to left. Fortran puts unary operations
> with addition and subtraction after exponentiation with exponentiation
> right to left. C does not have an exponentiation operator, but unary
> operations come before multiplication and division.
>
> When in doubt, use parentheses to make sure you get what you want.
>
>
​Very true. I do that if there is almost any chance that I, or another,
might not actually know which is first. I especially adopted this when I
learned a language called APL. It has _no_ precedence of operations. And it
does them from right to left. E.g. A=B*C+D is interpreted as A=B*(C+D). I
did programming in it for a couple of months. Then went back to normal
programming. Wrote completely _wrong_ code. When I asked a friend why the
calculation didn't get the "right" answer (2*4+3 == 14 was example I gave),
he looked at me like I was insane <grin/>. ​


-- 

Schrodinger's backup: The condition of any backup is unknown until a
restore is attempted.

Yoda of Borg, we are. Futile, resistance is, yes. Assimilated, you will be.

He's about as useful as a wax frying pan.

10 to the 12th power microphones = 1 Megaphone

Maranatha! <><
John McKown

	[[alternative HTML version deleted]]