RPN programming perplexity driving me nuts

11292017, 08:53 PM
Post: #1




RPN programming perplexity driving me nuts
Hi folks,
Maybe it's my advancing years (lol) or something, but I just can't figure out what is going on. Wrote a very simply RPN routine on my 15C and the "bug" seems to replicate on 11C so must be a logic issue. I just want to calculate X  1  X^2  1 (x minus 1, divided by xsquared minus 1) So this is what I put in: LABEL A ENTER 1  X <> Y X^2 1  / R/S The way I run it is just typing a number then issuing "f A" to run it. It seems not to work as intended if I do not press ENTER before issuing "f A" I thought the first ENTER (line 2) already puts the number I typed into both Y and X on the stack? And that I do not need to press ENTER before running the program, because whatever I typed (prior to issuing fA) is already in the X register? ??? 

11292017, 09:09 PM
Post: #2




RE: RPN programming perplexity driving me nuts
ENTER disables stack lift so the 1 on the next line overwrites X instead of raising it again.
The solution is to ENTER ENTER or ENTER then a nooperation (x<>y e.g.) A quirk that survives. Pauli 

11292017, 09:11 PM
Post: #3




RE: RPN programming perplexity driving me nuts
Try:
X^2 LASTX 1  X<>Y 1  / The problem is that ENTER duplicates the number, but also disables stack lift. HÃ¥kan 

11292017, 09:16 PM
Post: #4




RE: RPN programming perplexity driving me nuts  
11292017, 10:13 PM
(This post was last modified: 11292017 10:21 PM by Dieter.)
Post: #5




RE: RPN programming perplexity driving me nuts
(11292017 08:53 PM)lemontea Wrote: Maybe it's my advancing years (lol) or something, but I just can't figure out what is going on. This should have been resolved now: ENTER disables stack lift, so another ENTER is required. (11292017 08:53 PM)lemontea Wrote: I just want to calculate What about 1 + 1/x OK, except for x=1. ;) Dieter 

11292017, 11:13 PM
Post: #6




RE: RPN programming perplexity driving me nuts
Wow, thanks everyone.
3+ decades and somehow I got by without knowing that! Haha! 

11292017, 11:15 PM
Post: #7




RE: RPN programming perplexity driving me nuts
(11292017 09:16 PM)Philippe Wrote: Hi, Thanks, this is useful! 

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