Mach number - RPN vs. Algebraic - Printable Version +- HP Forums (https://archived.hpcalc.org/museumforum) +-- Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum-1.html) +--- Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum-2.html) +--- Thread: Mach number - RPN vs. Algebraic (/thread-43770.html) |
Mach number - RPN vs. Algebraic - Valentin Albillo - 10-05-2003 r. d. bärtschiger posted: "Whenever I buy another type of calculator I always use the following equation, from page 106 of the HP-67 Owner's Handbook, to test the useability of the new calculator. Using an HP calculator usually takes about 45 seconds to get the correct answer. Using an algebraic calculator usually takes much longer, twenty minutes or more, if it in fact can solve the problem at all." With all due respect, and not to doubt your words but your quoted figure and comment "twenty minutes or more if it in fact can solve the problem at all" seems a bit misleading and a lot unfair. 20 *minutes* ? Are you serious ? If you are, it seems to me to be a typical case of a "language" chauvinist, using ineptly a "language" he dislikes, then pointing out how bad and inefficient are the results he inefficiently produced. You'd have a similar case if someone profoundly disliking RPN were to solve this particular Mach number example using RPN: he would take ages to solve it, would do a lot of false restarts and unnecessary stack manipulations, then would complain how much RPN sucks. Simply preposterous. "Even trying to enter this equation into an HP-48GX or 49G+ equation writer is a difficult task."
Maybe that's the case for those calculators, but this "difficult" evaluation is a piece of cake for my SHARP PC-1350. The formula is entered like this: Sqrt(5*(((((1+.2*(350/661.5)^2)^3.5-1)*(1-6.875E-6*25500)^-5.2656)+1)^.286-1))where Sqrt is the "square root" symbol (a single keystroke). I timed myself entering this equation, exactly as written, and it took me 60 seconds flat (not "20 minutes"), the displayed result being 0.835724535, correct to all digits shown. If it actually took you 20 minutes, this only shows just how inefficient you are entering and evaluating algebraic expressions, or else just how bad your algebraic calculators are. "If you really want to see how much easier RPN is, try to calculate the answer to this problem using an algebraic calculator. [ ... ] I think you will agree the HP is easier."
No, I don't agree at all, by the simple reason that it isn't true, and your example is actually flawed. Why do I state this ? Let's see:
The point is: don't get me wrong. I've been using RPN for the past 20 years, like it very much, and, honestly, there's very few people in this forum or out that can do any calculation or program more efficiently in RPN than I can, even if it isn't proper I would say so myself. But just the same, and for that same reason, I can't suffer seeing RPN being "defended" with such pathetic arguments and such flawed, obsolete, no-longer-valid examples, much less seeing a lot of people being mislead by them into a false feeling of superiority which isn't exactly justified by examples like yours. Just you try to use this Mach number example to demonstrate the "superiority" of RPN in your HP to someone having a decent algebraic calculator (even if it is as old as the Sharp PC-1350) and you'll only succeed in making a fool of yourself, and proving the other person just how pathetic those "RPN nerds" are. It goes without saying that this is no good to the RPN cause, at all. Long live RPN ! Best regards from V.
Edited: 5 Oct 2003, 2:39 a.m.
Re: Mach number - RPN vs. Algebraic - Ed Look - 10-05-2003 Well, given your arguments, I will (tomorrow sometime; I'm so tired, have to teach Sunday School tomorrow morning, and don't what the heck I'm doing up on this forum [it's 2:30 AM in NYC]) give it a try on my Casio fx-4200p just to see if it is hard or easy. But that wasn't really why I am posting: I was able after seeing a correct display of the equation, to do the calculation on a one-line, four-stack machine, the HP-34C, without having to commit the first innermost term to a memory register. It wasn't necessary. Even with so many nested parentheses, it appears four stack levels is most often enough.
Incidentally, you do make some very good points and I generally agree with you. But I still think that I'll take the five or six steps I saved with RPN entry any day... for that reason, as the smallest economy in finger presses is worth it to me.
Re: Mach number - RPN vs. Algebraic - r. d. bärtschiger. - 10-05-2003 I entered your listing of the equation exactly as you wrote it above into a ti-92+, is that modern enough of a calculator for you? Upon pressing enter, it returned 'error syntax'.
rdb.
Re: Mach number - RPN vs. Algebraic - Namir Shammas - 10-05-2003 rd, I wrote an expression parser in C# and it gave me a Nan result, because it tripped over the part "*(1-6.875e-6*25500)^-5.2656)" ... when I wrote it as "/(1-6.875e-6*25500)^5.2656)" I got the answer instantly.
Namir
Re: Mach number - RPN vs. Algebraic - Les Bell - 10-05-2003 Singularly unimpressive, Valentin. I just grabbed my trusty Jeppesen-Sandersen CR-5 "whizz wheel", place the Calibrated Air Speed opposite the Pressure Altitude, move the cursor to the correct Indicated Temperature, and read the Mach Number off the Mach Number scale. No keystrokes, no messy programming and the whole process takes about three or four seconds. Sometimes, the old ways are the best ways. . . <g> Best, --- Les Bell [http://www.lesbell.com.au]
Re: Mach number - RPN vs. Algebraic - Rodger Rosenbaum - 10-05-2003 If I have read your post correctly, it looks like you have replaced a single _*_ by _/_. When I do this, I get a result of .325625586602 instead of .835724535179 Re: Mach number - RPN vs. Algebraic - Rodger Rosenbaum - 10-05-2003 What's the problem with doing this on the HP48? Just put a 'tick' mark at the beginning and then type it in just as Valentin has it, with the "Sqrt" replaced with the square root symbol found on the keyboard. The 48 deletes one set of unnecessary parentheses, and evaluates the result as .835724535179 On my Casio fx-4000p - R Lion (Spain) - 10-05-2003 Quote:I needed three trials on this calc because, using RPN calcs for years, I've forgot a gold rule of algebraics: "open parens after sq root" I'm sure that if I was using this Casio dayly, or if I was using the ALG entry in my 48GX everyday, I had got the answer at first attempt, as I did with RPN and with the MetaKernel Equation editor. Matter of taste, matter of use. But... I prefer RPN.
Raul
Re: Mach number - RPN vs. Algebraic - Rodger Rosenbaum - 10-05-2003 Looking over Namir Shammas's post more carefully, I see that I overlooked the minus sign in front of the 5.2656
Re: Mach number - RPN vs. Algebraic - James M. Prange (Michigan) - 10-05-2003 Well, I normally use an RPN (actually, RPL) sequence, but when I'm
In the following, "\v/" stands for the square root symbol, "\<<" and
Here's the object with flag -53 set (Show all parens): %%HP: T(3)A(D)F(.);The same object with flag -53 clear (No extra parens): %%HP: T(3)A(D)F(.);The above look right in the equation writer and when evaluated, result in the answer which others have said is correct: .835724535179
Having what I know is the correct algebraic object, with implied %%HP: T(3)A(D)F(.);Actual evaluation time of either the algebraic object or the program is about a tenth of a second.
Regards, Edited: 5 Oct 2003, 7:37 a.m.
Re: Mach number - RPN vs. Algebraic - James M. Prange (Michigan) - 10-05-2003 PS:
Actually, leaving out the redundant spaces in the RPL sequence: 5 1 .2 350 661.5/2^*+3.5^1-1 6.875 10 6NEG^*25500*-5.2656NEG^*1+.286^1-*\v/Press either the SPC or ENTER key where a space occurs in the above.
Again, the "^" is entered by the yx key, "NEG" by the +/-
Regards,
Edited: 5 Oct 2003, 8:54 a.m.
random tangent - hugh - 10-05-2003 as a random spin off, i'd like to air some related gripes.
so far, no distinction has been made between aos and formula style
more recently, ive been exposed to more and more formula calculators
my gripes relate to the expression handling abilities and so far, ive
another of my pet hates, is the silly unary minus button on these
im still waiting for a model that gets all these right.
Re: On my Casio fx-4000p - Ed Look - 10-05-2003 Raul, I haven't used that Casio fx-4200p in MANY years. I'm just guessing that it's formula entry is like that of a Hp-32SII or HP-48G series calculator. If not, I'll have to wait even longer, as the only manual I have for it is on my computer's hard drive and I usually hate reading massive texts on the CRT.
Re: Mach number - RPN vs. Algebraic - Namir Shammas - 10-05-2003 Roger,
I removed the exponentiation to the negative number and replaced multiplication with division. This change remove the presence of the operatod ^- in this sequence, which can trip many interpreters (BASIC, and other runtime interpreter such as the one I used to evaluation the expression). Namir
Re: Mach number - RPN vs. Algebraic - WXYZ - 10-05-2003 I pretty much agree with everything. (Except some minor things, but what the hell)
You say that thats a flawed example.... could you give a good one?
Re: Mach number - RPN vs. Algebraic - David Brunell - 10-05-2003 I keyed Valentin's key sequence into my wife's lowly TI-30, and it spit out the correct answer after about 2 seconds. I also got the correct answer the first time on my TI-59, although I had to save the SQRT operation for last. I think if this calculation were important to someone, then he would write down the intermediate answers anyway, since keystroke errors are very possible even on an RPN machine.
Re: Mach number - RPN vs. Algebraic - Rodger Rosenbaum - 10-06-2003 Yes, I realized that when I noticed that the minus sign had been removed. One could also use more parentheses to solve this problem. Those people who typed this expression into their HP71's had this problem, I noticed, but the HP48 in algebraic mode apparently has different precedence in this case.
Re: Mach number - RPN vs. Algebraic - Wayne Brown - 10-06-2003 rdb,
I just wanted to say that I liked your example very much, and thank you for posting it. Although, I confess that I had difficulty using it until Mark Hardman posted the scanned image from the book -- all those brackets and parentheses were hard to keep straight. But the book version was very easy to do with RPN. I just wanted you to know that some people appreciated the effort you (and Mark) made and agree with your reasons for doing it.
Re: On my Casio fx-4000p - R Lion (Spain) - 10-06-2003 Sorry... I actually don't know the 4200p... If it helps, I will say that the 4000p and the famous 6300G have the same program "language", but I don't know if it is the same for the 4200p.
Raul
Re: Mach number - RPN vs. Algebraic - r. d. bärtschiger. - 10-06-2003 Thank You.
rdb.
Re: Mach number - RPN vs. Algebraic vs Basic - Vassilis Prevelakis - 10-07-2003 The same solution to the
formula is provided in the HP-85 owner's manual:
**vp
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