[billmcneale]

I used to be in love with RPN and owned multiple HP calculators (HP-41, HP-15) but RPN is cheating by offloading effort on the user.

When you see a complicated, parenthesized expression, it's up to you to figure out the deepest expression, enter it first, and then work your way out.

Standard calculators require more keystrokes but they can be entered without much thought, left to right. And these days, you can also edit and modify your input, so it's hard to justify RPN.

[kccqzy]

Why would you need to enter the deepest expression first?

[7thaccount]

I think they mean that for a complicated expression you have to spend more brain power figuring out how to input things with RPN. It is a little more common sense with infix.

[billmcneale]

Yes, exactly.

If you have

1 + (2 * 3 + (4 / 5))

The smallest key count with RPN is to start entering the deepest expression first:

4 ^ 5 / 2 ^ 3 * + 1 +

You can type it left to right but it takes more keys and is probably on par with standard paren arithmetic, which negates the RPN advantage

1 ^ 2 ^ 3 * 4 ^ 5 / + +