negative number raised to even power

[rprosperi]

(04-26-2015 05:33 PM)Thomas Radtke Wrote:  

(04-26-2015 12:47 PM)rprosperi Wrote:  ...and so I assume all HP algebraic machines (Pioneers at least) will behave the same way.

Are you using the +/- key? If so, a negative number is placed on the stack, and your result doesn't make me wonder.

If I type - 2 ^2 into my 10BII+ (initial value displayed is zero), it returns -4. Same with the 17BII in ALG mode..

Yes, I'm using +/-, as in [2] [+/-] [shift] [Y^X] [2] [=] produces 4 on both 10BII+ and 17BII.

Playing further however, I've discovered that:

Starting with 0.00 in display, I type:

[-] [2] [shift] [Y^X] [2] [=] yields 4

whereas [-] [2] [x^2] [=] yields -4

While one can argue the relative correctness of interpreting the order of precedence, one would not expect different results between [Y^X] [2] and [X^2]. If you watch as you type, you can see how and why, since the [X^2] returns its result immediately, which is then subtracted (from 0), while the former must wait for the final [=] to evaluate the full algebraic line following the precedence rules.

Very interesting, thanks for questioning my comments Thomas, it lead to another surprising discovery.