A case against the x<>y key

[hansklav]

(05-10-2015 12:49 PM)Thomas Radtke Wrote:  

(05-10-2015 10:43 AM)hansklav Wrote:  Well, as Paul Dale pointed out, on a four level stack RPN calculator then you will run into trouble (stack overflow, leading to a wrong answer, without warning), unless, of course, you make use of STO and RCL.

No need to. You can evaluate from right to left until the first two terms 1-2*3^4/5, which have to be .calculated befor adding the sum of the two rightmost terms.

1688.40894809 in x, then [3][ENTER][4][y^x][5][/][2][*][1][x<>y][-][+]

Fits a 4-level stack perfectly.

True, but my reply was to Mark Hardman’s post, who started the whole calculation from the left side, and then a 4-level stack will not suffice.

But Mark also wrote "Inside out, left to right", and possibly he meant for this calculation "first do the rightmost part from inside out, and then the rest (his listing) from left to right". Your solution partially uses that adagium.

(05-10-2015 12:35 PM)Thomas Radtke Wrote:  Would you mind stating which calculator manual this is from?

The author himself of said manual (the spiral bound version of the WP 31S User’s Manual) sent me the simplest fix, which is even one keystroke shorter than yours:

1688.40894809 in x, then [3][ENTER][4][y^x][5][/][2][*][-][1][+]

So no need to use either CHS or x<>y !

The relevant part of the corrected page will now look as follows:



I must admit that I didn’t think of the latter possibility myself, probably because mentally it also uses the addition of a negative and then the use of CHS is more intuitive.

So now we’re left with several solutions to the same problem.

The question is: which one should we teach to newbies?
I’ll come back to that later.

Hans