Can we have RPN back?

[Tim Wessman]

I assume he is talking about this thread in comp.sys.hp48 (or one of 3-4 others)

https://groups.google.com/forum/#!topic/...hD4M5M0wrU

If that doesn't show up for you for some reason, here are several relevant quotes by several people.

Quote:> It turns out (at least on this early emulator) that the x^y key actually executes y^x! So 3 ENTER 2 x^y yields 9 not 8. Is it just me, or does this seem illogical?

Just thinking out loud here...

You are making a false assumption, namely, that the first input is always called "Y", and the second input is always called "X". But that's not true in Prime, and in fact hasn't been true for a long time for most of HP's calculators. Stack levels are only named X, Y, Z and T in 4-level RPN, which all the old HP's had. But in RPL, since there are an indefinite number of stack levels, they are numbered, not named. And in algebraic logic, you can call anything whatever you want. For example, have you noticed the Nth root button? (Shift x^y). Not Xth root; Nth root. Why? Because that's what everybody else calls it, and that's how it's taught.

Therefore, calling the power key x^y, y^x, or just [^] (as some calculators do) makes no difference, since the name no longer represents the order of the inputs. You'll notice that almost all algebraic calculators out there call it x^y, not y^x, and nobody complains that they do it backwards. Even the entire HP 38/39/40 series has called it x^y since 1995.

Bottom line (formerly known as X): I'm rather sure that they chose x^y for Prime for the same reason that everybody else does: That's how it's taught. That's a powerfully compelling reason, when the calculator is primarily intended for education. On the other hand, there is no reason whatsoever to call it y^x, other than human inertia.

-Joe-

Quote:> It turns out (at least on this early emulator) that the x^y key actually executes y^x! So 3 ENTER 2 x^y yields 9 not 8. Is it just me, or does this seem illogical?

The x^y & y^x on old HP's was related to input order because they used a stack with registers called X, Y, etc.

The Prime is first an algebraic calculator. On all algebraics, it has been convention that x^y means (first number)^(second number), and logically x=first number & y=second number.

Even on the 50G, y^x doesn't make sense but was kept because "people were used to it", but its stack levels has numbers and not X, Y etc.

Note that the "first" forerunner of the 50G, the 28C, has the power operator simply as "^" (shifted function above the multiply key).

[BartdB]

Quote:Just to add on to what Joe said, I am the one ultimately responsible for the exact key text and positioning since I delivered the final artwork for the printing (Prime, 10bII+, 39gII, 30b).

That doesn't mean I am ultimately the decider on what all the keys do - that goes through many revisions based on feedback and adjustments as we develop a calculator and learn what should go where to best support its operation, but I *have* been the one with the most critical eye on things like consistent capitalization, fonts, x/y centering and so on.

I can't claim color choice though unfortunately... :-(

x^y was used in previous HP calculators as was said and doesn't have anything to do with the old XYZT stack. It is just a pure power operator. As has been discovered, it calculates just like on the 50g. True, it could have just been labeled ^ but personally I think that is kind of ugly and less clear to both the math experienced and the math inept.

One consideration that has not been discussed though is that y^x would not fit well on the key without messing up the vertical alignment. The 50g doesn't have "classic HP style" sloped fronts on the keys - nor does it try to fit everything onto the same key. With the sloped front key, you can't print over the boundary there for many reasons. The "tail" of the y would require either reducing the y height, shifting the whole assembly upwards, reducing the size or something like that in order to avoid encroaching into the sloped front of the key.

Summing up, the *only* group of people that have any confusion with x^y are those trying to bring the old 4 level stack naming forward when it hasn't been in use since the 28 series, and no new users (the primary target market for Prime) would benefit from y^x.

To be clear, the buttons function exactly like the 48 series did and no order of arguments has changed. I'm perfectly happy to discuss this again if desired and hope eventually this becomes the only or last issue of contention. :-)