From: dave at horsfall.org (Dave Horsfall)
Subject: [COFF] [TUHS] The most surprising Unix programs
Date: Sat, 21 Mar 2020 14:53:02 +1100 (EST) [thread overview]
Message-ID: <alpine.BSF.2.21.9999.2003211401080.11999@aneurin.horsfall.org> (raw)
In-Reply-To: <f47a30b8-884a-843b-d820-d9d4da21ba3d@tnetconsulting.net>
On Fri, 20 Mar 2020, Grant Taylor via COFF wrote:
> 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]
> [multiply]
> [b] [enter]
> [b] [enter]
> [multiply]
> [add]
> [square root] # to solve for c
[a] [square] [enter] [b] [square] [+] [sqrt] (You don't need those extra
"enter" keys, as the display is implicitly the top of the stack.)
> (12 keys)
7. Well, "square" also needs the orange "shift" key, so that's really 9,
but the number of keystrokes ain't exactly the point; it's not a race, but
a method of thinking.
> Conversely infix notation for comparison.
>
> [a]
> [square]
> [plus]
> [b]
> [square]
> [square root]
>
> (6 keys)
[...]
Well, it really comes down to the calculation that you are trying to
perform. Trivial example:
1 + 1 = -> 4 keys.
1 enter 1 add -> 4 keys.
I don't have an algebraic calculator right to hand, but I'd imagine that
solving a second-order polynomial (without a built-in program!) would
involve fewer keys when using RPN because of the stack for intermediate
results; a quick estimate is around 30 keys (with single-digit numbers) to
get one of the roots, and you could probably save the result of most of it
on the stack for re-use to get the other root (and the 42S groks complex
numbers as a bonus[*], but that's hardly as a result of RPN). The 42S
also has a handy "swap x/y" if the operands are the wrong way around,
another one to rotate the stack, etc.
You don't do Computer Science without being exposed to RPN, and I had to
wait for a salary-in-lieu payout (long story) before I could afford the
42S that I'd been drooling over (and forget the overpriced IR printer[#]).
[*]
1 +/- SQRT => "0.00 i1.00" (I have the display precision set to 2 because
I use it for monetary stuff a lot; the internal precision is 15 digits).
[#]
A dream of mine is to reverse-engineer the printer protocol, then grab it
using a laptop camera.
Here endeth today's HP-42S lesson...
-- Dave
next prev parent reply other threads:[~2020-03-21 3:53 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200320140308.4FBBB18C073@mercury.lcs.mit.edu>
2020-03-20 16:07 ` gtaylor
2020-03-20 20:33 ` mike.ab3ap
2020-03-21 3:53 ` dave [this message]
2020-03-21 4:11 ` paul
[not found] <202003132331.02DNVaxN061501@tahoe.cs.Dartmouth.EDU>
[not found] ` <7ec47fd97b1a3d383ffed428f21f5287@firemail.cc>
[not found] ` <CALMnNGjuQybT8_g_g498dOuV9OV67JEOn7Mz34vG1TeO9WrkYw@mail.gmail.com>
[not found] ` <cdef128a21d3ed60c79dc5253d761652@firemail.cc>
[not found] ` <20200317145723.GF26660@mcvoy.com>
2020-03-17 15:41 ` clemc
2020-03-17 22:48 ` dave
[not found] ` <alpine.BSF.2.21.9999.2003180908300.10777@aneurin.horsfall.org>
[not found] ` <c44be69f-846d-55f2-2709-8765f7f5fcc4@gmail.com>
2020-03-19 21:31 ` dave
2020-03-19 21:30 ` cym224
2020-03-19 21:48 ` stewart
2020-03-21 2:49 ` dave
2020-03-21 2:55 ` lm
[not found] ` <6D9CA6C2-BDF2-4BCA-9503-0F8415C594C9@guertin.net>
2020-03-20 15:40 ` gtaylor
[not found] ` <202003201640.02KGerlG470796@darkstar.fourwinds.com>
[not found] ` <0b0d0ba3-7eae-a844-cc9a-ae542edb302b@tnetconsulting.net>
2020-03-20 19:11 ` clemc
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