[TUHS] The most surprising Unix programs

Grant Taylor gtaylor at tnetconsulting.net
Sat Mar 21 02:07:39 AEST 2020


On 3/20/20 8:03 AM, Noel Chiappa wrote:
> Maybe I'm being clueless/over-asking, but to me it's appalling that 
> any college student (at least all who have _any_ math requirement at 
> all; not sure how many that is) doesn't know how an RPN calculator 
> works.

I'm sure that there are some people, maybe not the corpus you mention, 
that have zero clue how an RPN calculator works.  But I would expect 
anybody with a little gumption to be able to poke a few buttons and 
probably figure out the basic operation, or, ask if they are genuinely 

> It's not exactly rocket science, and any reasonably intelligent 
> high-schooler should get it extremely quickly; just tell them it's 
> just a representational thing, number number operator instead of 
> number operator number.

I agree that RPN is not rocket science.  And for basic single operation 
equations, I think that it's largely interchangeable with infix notation.

However, my experience is, as the number of operations goes up, RPN can 
become more difficult to use.  This is likely a mental shortcoming on my 
part.  But it is something that does take tractable mental effort for me 
to do.

For example, let's start with Pythagorean Theorem

    a² + b² = c²

This is relatively easy to enter in infix notation on a typical 
scientific calculator.

However, I have to stop and think about how to enter this on an RPN 
calculator.  I'll take a swing at this, but I might get it wrong, and I 
don't have anything handy to test at the moment.

[a] [enter]
[a] [enter]
[b] [enter]
[b] [enter]
[square root]   # to solve for c

(12 keys)

Conversely infix notation for comparison.

[square root]

(6 keys)

As I type this, I realize that I'm using higher order operations 
(square) in infix than I am in RPN.  But that probably speaks to my 
ignorance of RPN.

I also realize that this equation does a poor job at demonstrating what 
I'm trying to convey.  —  Or perhaps what I'm trying to convey is 
incorrect.  —  I had to arrange sub-different parts of the equation so 
that their results ended up together on the stack for them to be the 
targets of the operation.  I believe this (re)arrangement of the 
equation is where most of my mental load / objection comes from with 
RPN.  I feel like I have to process the equation before I can tell the 
calculator to compute the result for me.  I don't feel like I have this 
burden with infix notation.

Aside:  I firmly believe that computers are supposed to do our bidding, 
not the other way around.    s/computers/calculators/

> I know it's not a key intellectual skill, but it does seem to me to 
> be part of comon intellectual heritage that everyone should know, 
> like musical scales or poetry rhyming. Have you ever considered 
> taking two minutes (literally!) to cover it briefly, just 'someone 
> tried to borrow my RPN calculator, here's the basic idea of how they 
> work'?

I'm confident that 80% of people, more of the corpus you describe, could 
use an RPN calculator to do simple equations.  But I would not be 
surprised if many found that the re-arrangement of equations to being 
RPN friendly would simply forego the RPN calculator for simpler 
arithmetic operations.

I think some of it is a mental question:  Which has more mental load, 
doing the annoying arithmetic or re-arranging to use RPN.

I believe that for the simpler of the arithmetic operations, RPN is 
going to be more difficult.

All of this being said, I'd love to have someone lay out points and / or 
counterpoints to my understanding.

Grant. . . .
unix || die

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 4013 bytes
Desc: S/MIME Cryptographic Signature
URL: <http://minnie.tuhs.org/pipermail/tuhs/attachments/20200320/6c9c556f/attachment.bin>

More information about the TUHS mailing list