WP 34S mini-challenge

[Gerson W. Barbosa]

(01-22-2014 01:12 PM)Dieter Wrote:  

(01-21-2014 04:07 PM)Didier Lachieze Wrote:  Well, here is a solution working on both the 42S and WP 34S, not limited to integers and where I don't see the rounding error highlighted above:

Code:

00 {15-Byte Prgm}
01 LBL "GS"
02 X^2
03 RCL+ ST L
04 1/X
05 RCL+ ST X
06 1/X
07 END

Have you tried n = 7 ?-)

Consecutive 1/x commands are prone to roundoff errors. I do not have a safe five-step solution, but if one additional step is okay, this should yield accurate results:

Code:

01 LBL "GS"
02 X^2
03 RCL+ L
04 SIGN
05 STO+ X
06 STO/ L
07 X<> L
08 END

Dieter

What is wrong with 28.0000000001? That's a perfect 28 for all practical purposes :-)
Of course the original formula (n^2 + n)/2 is better because it always yields exact results for integer arguments (even when using binary number formats), but occasional errors of a few ULP's are acceptable (and expected) when using a digital computer or calculator, IMHO.

Regards,

Gerson.