negative number raised to even power

[Joe Horn]

(05-04-2015 06:10 AM)Dirk. Wrote:  So how do you explain your students that 2(+/-)² is -4 at the prime when entering it using the keyboard?

It's quite simple, really. Notice that you typed it as "2(+/-)²", which shows that you are assuming that keystroke order should always matter, which is true in RPN... but it does not (and SHOULD not) always matter in command-line calculators (the reason follows shortly). Prime is a command line calculator, and the command line is not evaluated until Enter is pressed. At that time, the order in which the keys were pressed is totally immaterial; the ONLY thing that matters are the rules of parsing the algebraic syntax on the command line. In those rules, "-2²" means "start with 2, square it, then negate the result".

In ANY command-line algebraic-notation calculator which follows standard algebraic notation rules of operator precedence, [2][+/-][x²] yields the same result as [+/-][2][x²], because both key sequences create identical command lines, namely, "-2²", which of course IN STANDARD ALGEBRAIC NOTATION equals -4.

(05-04-2015 06:10 AM)Dirk. Wrote:  In my opinion this is simply a bug which needs to get fixed as soon as possible.
(Sorry for my harsh tone, since I'm German, I can't do better :-) )

I'm half German, so I half understand. But my Irish half wants to write a sad song about how we algebraic users are so often misunderstood. Let's compromise by enjoying some Weihenstephaner Hefeweissbier and Guinness, and let the others fight it out.