RPN/RPL is still relevant

[Alvaro]

How many people in the World do use RPN/RPL?
Is it already dead?
I doubt very much that HP will continue on that path.
For me, at least, HP did miss the oportunity to rebird their Calc´s business stay with a obsolet programing language.

[Han]

(04-10-2014 06:39 PM)Matt Agajanian Wrote:  Although I adhere to LSTx as a fine example of an error recovery tool, how do you see the efficiency and usefulness of 'Last X' on non-RPL HP's?

Unless I misunderstood something, this would be simple if implemented correctly. An algebraic/textbook entry method would implement last x as "last command" so that one would simply recall the last command line and edit the mistake there.

For example, I might type in

\[ \frac{2x+3y-5^3}{5\sqrt{4x-1}+4} \]

only to realize that the part within the square root should have been \( 4x+\pi \) and not \(4x -1 \). I simply use the "last command" (undo) feature to recall the most recent command line, have the formula above reappear, and make a minor edit. On the HP Prime, I would simply copy it from the command history with a touch of the screen. Of course, not all non-RPL HP's have this feature.

In terms of keystrokes, it's still more than RPN (because one must navigate the cursor appropriately in textbook mode), but it's not irrecoverable.

[Han]

(04-10-2014 06:46 PM)Alvaro Wrote:  How many people in the World do use RPN/RPL?
Is it already dead?
I doubt very much that HP will continue on that path.
For me, at least, HP did miss the oportunity to rebird their Calc´s business stay with a obsolet programing language.

Anyone who works in finance and does a lot of number crunching (even the clerk behind your bank's counter) will likely be using RPN machines -- though not necessarily from HP. Even some cash registers operate in RPN. A new calculation starts by clearing registers to 0, and then one proceeds to add (for example) by typing in a number and pressing + and repeating with another value followed by +. Because the interface is always buttons (for each digit and the basic four operations), input efficiency is a must and there's no beating RPN when it comes to efficiency.

[Matt Agajanian]

Ah, Han! I see where you're going with this.

As I've seen recently, scrolling through a history list allows a user to retrieve a full calculation, make adjustments/corrections and so forth. A very convenient undo method.

So, it seems that a scrollable display, 'Ans' key, and copy/paste functionaities have enhanced the Undo option.

[Han]

(04-10-2014 07:04 PM)Matt Agajanian Wrote:  Ah, Han! I see where you're going with this.

As I've seen recently, scrolling through a history list allows a user to retrieve a full calculation, make adjustments/corrections and so forth. A very convenient undo method.

So, it seems that a scrollable display, 'Ans' key, and copy/paste functionaities have enhanced the Undo option.

Indeed -- and if done right, it would not be too difficult for complete beginners to learn how to program. One idea that many folks have surely thought about is a way to save one's work on, say, the HP Prime. I propose that we go a step further and not just enable one to save their work, but to then be able to easily turn the saved "work" into a program. Since a history is kept of all calculations on the display/history stack, imagine if the user could save that history into a text file. Then the user adds in a few lines of "code" that turns those sequences of commands into program (since a program is nothing more than a sequence of commands, right?). On the HP Prime, this is just a matter of appending

Code:

EXPORT ProgName() <-- possibly insert some parameters, if needed
BEGIN

to the beginning and an END to the end. Now they suddenly have a program that solves that particular kind of problem and they didn't really have to learn much of any programming whatsoever. It's even better than RPN programming because you essentially get to try out the solution first, and once you figured out how you want things to go, just save the history and turn it into a program.

An analogy would be, say, in Maple or Mathematica (or whatever other software you use as a CAS) saving the "worksheet" and then changing only a few minor parameters in the worksheet, and then re-running the worksheet.

This is much, much better than keystroke programming. And, pedagogically speaking, there is a much easier transition from problem solving to programming if you introduce programming to students this way.