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What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

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Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#111

Post by MaxBarraclough »

MaxBarraclough wrote: post #106
agumonkey wrote: post #2

I like to repeat everywhere that HP48 series had code block syntax with arrow notation. a a + >> (double function) Those machines were well before their time.. I hope the makers had fun, it's really sad it's gone from the market although one could say that ES6 in your smartphone browser is your modern day HP48 reincarnation.

Here's my take on the Forth equivalent. Defining a DOUBLE word, the usual way, rather than anonymously. (Tricky to pick a good identifier that doesn't sound like it's doing something with double-precision floats.) ( num -- num_doubled ) : DOUBLE DUP + ; Next up, we push 7 to the stack, define our 'function' (not a Forth term) anonymously using :NONAME which pushes an execution token value to the stack, then we immedi…

Too late to edit: the second example leaks memory, as the execution token is not destroyed before becoming inaccessible. As far as I know, ANS Forth doesn't offer a friendly interface for destroying execution tokens.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#112

Post by hpfr »

hota_mazi wrote: post #76
rbanffy wrote: post #6

It's simpler to implement RPN than algebraic notation with precedence. The latter requires an operation stack where operations are stacked until they encounter a lower precedence operator or the user presses =. The user types less, the computer does a lot less. I find it fun to think in RPN.

Yes, the user types less but they have to think more. Don't get me wrong, I love RPN and I've had a stream of HP calculators through my college years (synthetic programming on the HP41!), but... they come at a cognitive price. When you see an expression, you have to process the precedence in your mind to find out the most nested expression and start entering from there. Basically, the calculator is cheating by forcin…

That’s the point. This precedence processing should be intuitive if you’ve learned to do calculations by hand, and it helps you understand the expression as you enter it which makes for easier error detection. It’s also nicer for building up an expression on the fly as opposed to the Answer key on standard calculators.

If you’re just copying existing expressions, you might as well use one of those OCR calculators.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#113

Post by m463 »

fsckboy wrote: post #110
m463 wrote: post #19

Reading these comments, I'm surprised that people think in RPN. (I mean I shouldn't be, I just didn't think of it) I wonder if teaching it early on, instead of parenthesis, would have made math lessons different? Could there have been different notations used for things like factoring out a quadratic equation?

> Could there have been different notations used for things like factoring out a quadratic equation? well, you're talking about high school algebra, but just adjacent to that is the lisp programming language which uses polish notation. It also uses parentheses because parsing the parentheses-less polish notation requires that the operators have a fixed number of operands Sussman, co author of SICP and co creator of l…

Well. just. wow.

I was just thinking of notation, but making math parsable, or teaching a regular math notation, that should be a thing.

I remember hearing generalizations like "chess is pattern matching", and "math is just symbol manipulation", but latter really comes to life if we make math notation regular enough to be funamentally machine readable.

Just think what it could do with ai (or for ai)

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#114

Post by todd8 »

I was first exposed to RPN around 1963. It was a game my aunt gave me as a present. I wish I could remember the name of the game. Players rolled dice that had logical operators and perhaps quantifiers on the faces of the dice. The goal was to construct valid logical expressions using RPN. Even for a kid that was nuts about math, the game wasn’t that interesting. Does anyone remember what I’m talking about? I’m not sure of the year, but I think there might have been ads for the game in the magazines I read, like Popular Electronics or Scientific American.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#116

Post by alan-crowe »

todd8 wrote: post #114

I was first exposed to RPN around 1963. It was a game my aunt gave me as a present. I wish I could remember the name of the game. Players rolled dice that had logical operators and perhaps quantifiers on the faces of the dice. The goal was to construct valid logical expressions using RPN. Even for a kid that was nuts about math, the game wasn’t that interesting. Does anyone remember what I’m talking about? I’m not su…

Was it WFF 'N Proof? https://en.wikipedia.org/wiki/WFF_%27N_PROOF

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#117

Post by hota_mazi »

hpfr wrote: post #112
hota_mazi wrote: post #76

Earlier quoted context omitted.

Yes, the user types less but they have to think more. Don't get me wrong, I love RPN and I've had a stream of HP calculators through my college years (synthetic programming on the HP41!), but... they come at a cognitive price. When you see an expression, you have to process the precedence in your mind to find out the most nested expression and start entering from there. Basically, the calculator is cheating by forcin…

That’s the point. This precedence processing should be intuitive if you’ve learned to do calculations by hand, and it helps you understand the expression as you enter it which makes for easier error detection. It’s also nicer for building up an expression on the fly as opposed to the Answer key on standard calculators. If you’re just copying existing expressions, you might as well use one of those OCR calculators.

The point is not really whether it's intuitive or not (and for very nested expression, it's really not always intuitive to find the most nested one, especially if you have to remember precedence laws).

The point is that it takes time.

As much of an RPN fan I am, I am not convinced that the time it takes my brain to identify nested expressions is smaller than the time it would take me to just type the expression left to right on a regular calculator.

Re: What Is RPN? Why Did/Does HP Use RPN? Learning RPN (1999)

#118

Post by todd8 »

alan-crowe wrote: post #116
todd8 wrote: post #114

I was first exposed to RPN around 1963. It was a game my aunt gave me as a present. I wish I could remember the name of the game. Players rolled dice that had logical operators and perhaps quantifiers on the faces of the dice. The goal was to construct valid logical expressions using RPN. Even for a kid that was nuts about math, the game wasn’t that interesting. Does anyone remember what I’m talking about? I’m not su…

Was it WFF 'N Proof? https://en.wikipedia.org/wiki/WFF_%27N_PROOF

Yes, it was! Thanks so much, I just couldn't remember the name of that game. How did you recall it from over half a century ago?

Looking up used editions of WFF'N Proof on Amazon I recognize the instruction book published in 1965. That must have been around the time I received the game. It looks like more recent sets were more extensive.

Well, the game likely had a positive influence on me, I ended up with a Math degree in college. Even in high school, I understood logic and proofs better than the other kids in my school.

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