#reverse polish notation

[nojewelsnonothing]

There's a minor update to my Hypatia RPN calculator for Windows, the new version is 5.2. I'm biased, of course, but it's a really great tool for anything from the most simple arithmetic calculations to complex iterations or Monte Carlo experiments, and it's free and open source.

https://hypatia-rpn.net

[nojewelsnonothing]

Hypatia 4.5 is here — you can download the new version of my RPN calculator for Windows computers. It is free, open source, and fully portable. To quote from the website: “Apart from the usual functions of a scientific pocket calculator and a number of built-in unit conversion functions, Hypatia knows named variables, lets you define your own constants, lets you define your own functions and write your own scripts, knows hexadecimal and binary numbers, lets you read data from files and save results to files, has count and condition controlled loops, If/Then/Else clauses, can do iterative calculations, knows three kinds of random numbers, lets you perform Monte Carlo experiments, lets you calculate generalized Fibonacci sequences, lets you export sequences of results, etc., etc.” It is still easy to use for quick and trivial calculations or unit conversions. I have to warn you, though: Hypatia is a text-based console program, you have to use the keyboard instead of the mouse. I also have to warn you that it says, “do not use Hypatia if you support intolerance, fascism, racism or misogyny.” https://hypatia-rpn.net If you have any questions, feel free to ask them!

[nojewelsnonothing]

Hypatia 4.1 — I've uploaded a new version of my programmable RPN calculator app for Windows (RPN is "Reverse Polish Notation"). Idiosyncratic as it is, once you've got a little accustomed to it you can easily use it for quick simple or not so simple calculations, but its many features, including named variables and scripts with loops and If/Then/Else clauses, also make it a powerful tool to deal with far more demanding calculation tasks. Still it has a very small footprint — the download zip file, including the exe file (no installation needed) and the PDF manuals, is less than 1 MB. Free, of course, and open source. If you have any questions, problems or suggestions, let me know.

https://hypatia-rpn.net

[dehex18]

My hottest take is that RPN calculators are better than infix notation calculators.

[laejoh]

acey_ducey.el

A few days ago I posted a BASIC computer listing of the game "Acey Ducey". Here is the final Elisp Emacs translation:

And here is a sample run:

[laejoh]

A fun way to learn a computer language is to recode old BASIC Computer games.

Here's a ZX81 BASIC version of Acey Ducey:

Here's Acey Ducey in Emacs Elisp:

[steckasaurus]

[charlietokyojp]

http://ameblo.jp/number-refugee/entry-11160529790.html

日本語と逆ポーランド記法が似ている件がわかりやすく解説されている。

15年程前に仕方なしにC++のコードを書いた際に一応は学んだが忘れつつあったのでおさらいした。

A＝1，B＝3，C＝5，D＝4，E＝2 のとき，逆ポーランド表記法で表現された式 AB＋CDE／－* の演算結果はどれか。 by 基本情報技術者 平成22年春期 午前問3

答えは12。 「AB+CDE/-*」にそのまま数字を代入し演算子を展開すると「1+3*5-4/2」となって、通常の四則計算をしてしまい、答えが「1+15-2=14」になるので注意が必要。

演算子は直前の2つの数字に対し適用するから、左から順番に細かく（）で括ると、 (A+B)*(C-(D/E)) ということになる。 A+B=1+3=4 D/E=4/2=2 C-2=5-2=3 4*3=12

後置換記法（逆ポーランド表記法）では，例えば，式 Y＝(A－B)×C を YAB－C×＝ と表現する。 次の式を後置換記法で表現したものはどれか。 Y＝(A＋B)×(C－(D÷E))　by 応用情報技術者 平成22年秋期 午前問1

答えは YAB+CDE/-*= で前述のものと同じ。=とYの記述が増えただけだ。

The Polish logician Jan Łukasiewicz invented this notation in 1924 in order to simplify sentential logic. -Wkipedia

ポーランド人は数学に強いと思う。「インド式」と同じく「ポーランド式」は特別に感じる。2人しかいないポーランド人の知り合いは、どちらも計算が速い。算数に強く細かい計算が得意というわけではなく、答えの近似値を求めるのが速い。

逆ポーランド記法を見ると、チェスや暗号アルゴリズムの脳に近い気がする。最初にエニグマを解読したのものポーランド人だったことから、独自の思考を持っているように思う。

いろんな国の算数の授業を受けてみたい。