RPN/RPL is still relevant

[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.