on the RPN mentioning sharp pc-1211, v.albillo, el-506w and recurring topics

[pier4r]

(12-06-2017 11:46 AM)Nigel (UK) Wrote:  On the subject of RPN versus equation entry logic, I'd just like to mention the Acron RPN calculator app, available for Android and IOS. This is an RPN entry calculator that builds up a stack showing both the number in each level and the algebraic expression leading to that number. (See the link above for some screenshots.)

Interesting I need to try it and compare vs the 506w that so far seems the best in "don't be mad for a typo".

[Claudio L.]

(12-04-2017 07:55 PM)franz.b Wrote:  you made me think of an important detail: seeing partial results helps a lot in understanding what you are doing and prevents gross errors, as has already been said.

This is crucial for engineers. If you do plain math, then there's probably no need. If you are just applying a formula you found in a book (like students do), there's no advantage, but if you are reasoning a problem as you compute it, there's no substitute.
A rough example:
Have a pressure, need to estimate a tributary area, or measure it from CAD. Just plug the numbers and get the force. Right on you think, uh! 50000 N, I'm going to need some serious steel to support this. Let's try with a 200 mm shape: compute a bending moment, so that force times L/4 if it's simply supported. DUP that in case I need it for a second try. Divide by the section modulus of the trial shape, and boom, too much stress. DROP to get my moment back, and try a slightly thicker shape, now I like it. Just write the selected shape on CAD and move on to the next problem.

Somebody might think it's backwards: You can solve the problem in advance algebraically, and get a formula to extract the necessary section modulus, then select the shape from there. But that's how I think and works for me. It allows me to stop in the middle and change a design if I think "oh, there's no way I can have 50000 N here, I'll run beams the other way to send some of this force somewhere else, will be much more efficient". Without seeing those intermediate results, I don't "feel" the forces and can't visualize how things will behave.

By the way, the above works so much better on an RPL machine than RPN. Because you get the best of both worlds: You can have algebraic formulas whenever you need them (use the right tool for each job), and you can save as many temporary results as your brain can handle.

So the eternal wars of algebraic vs RPx are pointless, just use the tool that integrates best with your workflow. In my case, RPL it is.

[Massimo Gnerucci]

(12-06-2017 02:39 PM)Claudio L. Wrote:  So the eternal wars of algebraic vs RPx are pointless, just use the tool that integrates best with your workflow.

Amen, Claudio.

[Maximilian Hohmann]

(12-06-2017 02:39 PM)Claudio L. Wrote:  So the eternal wars of algebraic vs RPx are pointless, just use the tool that integrates best with your workflow. In my case, RPL it is.

For what you describe I would use Excel today... (*) And back when I was required to perform simiar calculations I would use STO and RCL on my Ti59 instead of DUP and DROP.

(*) With the benefit that you can directly copy-paste your numbers into the paperwork than has is supposed to supply nowadays with the parts that one designs.

[Guenter Schink]

(12-05-2017 11:22 PM)pier4r Wrote:  The free42 worked in one go. I did it again and I pressed a wrong function, and there was no undo (not that I know at least). That was frustrating.

Could you be more specific? Undo a function usually is simply done by the reverse function e.G pressed "SIN" do "ASIN" or pressed "/" do LASTx and "x"

Or when you don't want to waste a place on the stack after a wrong [/]* do [RCL] [x] [.][ST L]

* [/][x] for divide and multiply
But what was the problem?

Günter

[brickviking]

(12-06-2017 02:53 PM)Massimo Gnerucci Wrote:  

(12-06-2017 02:39 PM)Claudio L. Wrote:  So the eternal wars of algebraic vs RPx are pointless, just use the tool that integrates best with your workflow.

Amen, Claudio.

Totally agree, but that's just my opinion. Thankfully this place has far less flamewars.

(Post 144)

[pier4r]

(12-06-2017 07:53 PM)Guenter Schink Wrote:  do LASTx and "x"

Or when you don't want to waste a place on the stack after a wrong [/]* do [RCL] [x] [.][ST L]

* [/][x] for divide and multiply
But what was the problem?

Günter

Interesting. The problem was that I had Y with a value (likely the first factor of the formula) and X with a value (the current second factor), then I mistyped (due to a little distraction) and I did not pay attention about what function I pressed (having an history could have saved me). I knew it was a shifted function though.

Last X got me back the X register, but the Y was gone.

[Guenter Schink]

(12-06-2017 10:51 PM)pier4r Wrote:  [then I mistyped (due to a little distraction) and I did not pay attention about what function I pressed (having an history could have saved me). I knew it was a shifted function though.

Ok that explains it.
Günter

[Frido Bohn]

(12-05-2017 11:22 PM)pier4r Wrote:  \[ \frac{57^{6}}{22 \cdot 24} - \sqrt{ 53+81 } - \frac{ 25 - 7 \cdot \sqrt{92 \cdot 82} }{4^{2} \cdot 13 \cdot 81 } \]

I need 9 strokes for this (RPN @ HP25).

Quote: Counting numbers as 1, operations as 1, change of sign as 1.

Rationale:
The first part of the "formula"
\[ \frac{57^{6}}{22 \cdot 24} \]
renders a number of 8-digit magnitude. The rest of the expression can be neglected (at least from a practical, i.e. real-world point of view).

[pier4r]

yes that is true.

I built the formula randomly picking operators from a limited list and numbers between 1 and 100.