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10.4: Be aware of a Calculator widget bug
Authored by: gleam on May 24, '05 01:21:52PM

Actually, in RPN, if you wanted to do 1+2*3 you would do 1 2 3 * +.

Well, I would do 2 3 * 1 +, but that's me.

I don't think either is more or less intuitive. You think 1+2*3 is more intuitive because you grew up seeing it written out as 1+2*3. If you'd seen it written out 1 2 3 * +, you'd think RPN was intuitive. It's all stuff you learned at some point, you didn't innately know that + meant plus, for instance.

Anyway, on calculators the big advantage of RPN is that it saves you keystrokes.

An example:

you want to calculate ((2*8)+(9*3))/((1/7)-(5*9))

That's pretty much how you have to write it on most non-rpn calculators. you might be able to eliminate a parenthesis or something, but otherwise you're left to type in all that crap.

RPN: 2 8 * 9 3 * + 1 7 / 5 9 * - /

14 keystrokes vs 28. As the complexity increases so, generally, do the savings from using RPN.




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10.4: Be aware of a Calculator widget bug
Authored by: jlaro on Sep 30, '05 09:07:32PM

Actually, it's 19 vs 19 keystrokes, not 14 vs 28. For the RPN you forgot to count the ENTERs between values (otherwise 2 8 is 28), and for non-RPN there were too many parenthesis as you said (and the last one can be dropped because = closes it automatically).

I admit, I never used an RPN calculator before writing this post. The big difference seems to be that with RPN you have to memorize which groupings interact with which, and how, to put operations at the right place, whereas with the normal method the machine does it for you if you follow exactly the written equation (with SOMETIMES extra parenthesis to make sure the machine understands correctly).

Question to RPN experts, how would you enter the quadratic solutions (-b+SQRT(b^2-4ac))/2a and (-b-SQRT(b^2-4ac))/2a ? I tend to think that a lot of memorizing is necessary.
24-keystroke non-RPN example: ( - 2 + ( 2 x2 - 4 * 3 ± * 8 ) SQRT ) / ( 2 * 3 ± =

I guess it's just like reading sheet music, anybody can get used to anything.

(somehow ± can be shown here, but not the square root sign, hence my use of SQRT)



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