

RPN Ever 4 - wlll
http://37signals.com/svn/posts/2760-rpn-ever-4-
Get your nerdon.
======
shubber
Funniest thing is "RPN sounds like a joke" - like they're discovering it for
the first time. Isn't RPN the next chapter after hexadecimal in The Short
Course for Computer Geeks?

New tech interview question:

1 2 + 3 * 4 - 5 / =

~~~
burgerbrain
Seriously, RPN was freshman year stuff for me. Did all the schools somehow
ditch the classic "write a calculator" assignment?

~~~
el_chapitan
I recall learning prefix before I learned RPN. Then again, our teaching
language was scheme. Writing an RPN calculator was one of the first homework
assignments, though.

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cromulent
My dad worked for HP when I was at high school so I had a 12C. It was great,
mostly because no-one else would just "borrow it for a second" due to the RPN.

A few years later I bought a paddock car for $150 (for a demolition derby on a
friend's property) and it had a 12C in the glovebox. I sold it for $100. 150
[enter] 100 [minus] = $50 car.

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amalcon
I know a guy who likes to tell the following story about how he learned RPN:

Back in college, his calculator battery died right before a big test. He
borrowed his roommate's calculator. It was an HP calculator.

After failing that test, he made a point to both learn RPN _and_ always keep
extra batteries.

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tzs
HP has official HP calculator apps on the iOS app store. There's a 12c for
$15:

[http://itunes.apple.com/us/app/hp-12c-financial-
calculator/i...](http://itunes.apple.com/us/app/hp-12c-financial-
calculator/id318954345?mt=8)

A 12c Platinum for $20:

[http://itunes.apple.com/us/app/hp-12c-platinum-
financial/id3...](http://itunes.apple.com/us/app/hp-12c-platinum-
financial/id328224790?mt=8)

Finally, a 15c for $30:

[http://itunes.apple.com/us/app/hp-15c-scientific-
calculator/...](http://itunes.apple.com/us/app/hp-15c-scientific-
calculator/id318956846?mt=8)

~~~
nas
Emulation is a good idea. HP spent a huge amount of resources to try to ensure
their calculators return the best possible numeric results. It is an issue
many people forget about, for example, compare the statistical function
accuracy of Excel vs R or Gnumeric.

As an example in the calculator world, I like free42 and had it installed on
my Palm. However, I don't have the same confidence in it as I have in my HP-48
or my HP-35s. If I'm doing engineering calculations then I really prefer to
use a real HP calculator or an emulated one using original firmware.

~~~
roxstar
One of the sad things though is that hp has really declined in quality
calculators, if you look around you'll find quite a few problems regarding
accuracy in the new 35s close to critical values. (Though they may have
updated the software version since my purchase a few years ago)

I do like my giant hp50g for anything that doesn't need matlab though, and the
35s is still pretty good despite its errors (especially since I know where the
errors exist).

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mcculley
I have a 48SX on my desk that I use almost every day. It's not just the
notation and interaction that is nice as there are plenty of calculator apps
that support RPN. The tactile feel of the keys gives good positive feedback
that you haven't missed a digit when calculating in a hurry.

~~~
alexg0
apt-get install rpncalc

~~~
SageRaven
Better yet: "apt-get install x48"

~~~
alexg0
E: Unable to locate package x48 :-(

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ScottBurson
I'm sure that part of the reason I found Lisp syntax so natural, when I first
encountered it, is that all the time I had spent in high school using RPN
calculators had already warped my brain^W^W^W helped me escape from the
tyranny of being able to think only in infix.

~~~
arethuza
Many years ago I was working on a project that required development in Lisp, C
and PostScript. If sort of agree that jumping from Lisp to PostScript and
vice-versa was somehow easier that jumping from either into the infix world of
C.

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alexg0
For all the die hard RPNers, m48 and pcalc on iphone great replacements. m48
actually runs original HP48 and HP49 roms.
<http://itunes.apple.com/us/app/m48/id332100614?mt=8>

~~~
SkyMarshal
I just installed Droid48 on my Android, it looks really good so far too:

<https://github.com/shagr4th/droid48>

<http://www.appbrain.com/app/org.ab.x48>

------
KC8ZKF
I have a 12C as well. The OS X desktop calculator has an RPN mode, but the
very best RPN desktop calculator is Emacs Calc. It has an infinite stack, is
programmable with Lisp, and can even operate on formulas in other buffers.

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yason
Reverse-Polish notation is safe and good. I use M-x calc, mylsef.

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DarthShrine
I have an HP 35s which I found to be a lovely calculator which got me started
with RPN. Unfortunately, I wasn't able to use it at school for my final exams
since they had a list of specifically approved calculators (which the 35s
would never have made since it's programmable). I switched to the Casio
fx-82AU Plus which graphically displays your calculation, meaning you don't
have to keep track of the inside-to-out expansion of RPN or the mountains of
parentheses you usually require in algebraic mode. They're both good systems,
but I can see the graphical display being more useable for most people
(despite being awfully slow).

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cagey
My dad had a HP25 (not C), which was the first calc I ever used. I can't use a
algebraic calc (drives me nuts). I had an 11C, then a HP15C in college, sold
em both to get a HP71B. Now I collect these when I can. There's something nice
about holding the HP quality in your hand. I've picked up a number of HP48's
off craigslist over the years for cheap: I've never used them "in anger" but
wow they've so much better than the single-line display calcs (to say nothing
of their programmability) that got me thru college. My dad still uses his
HP32SII for engineering calcs on the go...

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wazoox
A friend of mine is so fond of HP calculators he wrote a complete language
inspired by RPN, Reverse Polish Lisp (RPL) : <http://www.rpl2.net/>

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proee
We put RPN mode on eCalc. Just click on the ALG menu button on the top right.

<http://www.ecalc.com/>

When we started with the project, I was a die-hard RPN guy. However, buy the
end I was converted over to using algebraic. There's a little tear in the
corner of my eye right now.

~~~
habitatforus
Being able to see the stack is a great feature. Thanks!

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tomkarlo
The default OSX “Calculator” has RPN support as well, just press cmd-R. Handy
to know if you forget your 12C.

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gchpaco
I'm so much an RPN geek that I have an HP 41CX emulator for my phone, because
my physical calculator isn't everywhere. (It's actually an excellent emulator,
but of course there's no tactile feel to be had from the keys, which I miss a
lot)

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samlittlewood
Don't forget the unix version:

    
    
       mac:~ sam$ dc
       2 2 + p
       4
       mac:~ sam$

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ilikejam
That is frankly awesome. People think there's something wrong with me for
using dc instead of bc in Unix shells.

Not sure I can justify £50 to buy the hardware version, though.

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bound008
This article deserves upvoting just for the title alone.

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muerdeme
Best calculator ever - HP 32Sii: <http://en.wikipedia.org/wiki/HP-32S>

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pqs
In high school and college I used a HP48GX first and then a HP49G. Now I'm
using Emacs Calc.

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NoSalt
I love my 48G ... it got me through Calc I/II/III and DiffEq.

