Cross Product

[rgallier]

Why won't this evaluate from Home in RPN:
CROSS([-6 4 12],[-0.3 0.4 0])

[kharpster]

(06-23-2015 01:17 AM)rgallier Wrote:  Why won't this evaluate from Home in RPN:
CROSS([-6 4 12],[-0.3 0.4 0])

It does if you enter it "RPN Style" ;-)


[-6 4 12] Enter

[-0.3 0.4 0] Enter

CROSS Enter

The displayed result is: [-4.8 -3.6 -1.2]

[rgallier]

I kept trying:
[-6 4 12] ENTER
[-0.3 0.4 0] ENTER
CROSS(2)

Why do some functions need the stack arguments and others don't. I know cross product is implied with two arguments. If you put in CROSS(2) the error message even shows:
CROSS([-6 4 12] , [-0.3 0.4 0]); this format works with some vectors in RPN Home!?!

[kharpster]

(06-23-2015 01:53 AM)rgallier Wrote:  Why do some functions need the stack arguments and others don't.

Do you have an example or two?

[rgallier]

erf() is one
http://h30434.www3.hp.com/t5/Calculators...-p/5047983

[rgallier]

This video discusses some others:
https://www.google.com/url?sa=t&rct=j&q=...Ww&cad=rja

[John Colvin]

(06-23-2015 01:53 AM)rgallier Wrote:  I kept trying:
[-6 4 12] ENTER
[-0.3 0.4 0] ENTER
CROSS(2)

Why do some functions need the stack arguments and others don't. I know cross product is implied with two arguments. If you put in CROSS(2) the error message even shows:
CROSS([-6 4 12] , [-0.3 0.4 0]); this format works with some vectors in RPN Home!?!

I think that the answer is CROSS doesn't require a stack levels specifier if entered as a command (CROSS Enter) because it always takes two arguments.

[rgallier]

I guess I was confusing the fact that CAS functions used in HOME require the stack argument; even if it is only one and always one. It just seems the UI inconsistencies provide for a confusing UX.

[kharpster]

(06-28-2015 03:21 AM)rgallier Wrote:  It just seems the UI inconsistencies provide for a confusing UX.

Yes, yes they do! At times it's almost like using two completely different machines...