UI is hell: four-function calculators

I realised reading this that, even though I used to be quite adept with these common four-function calculators, I have since forgotten most of their operation. The past ten years or so I have exclusively been using RPN calculators – I find them so much easier to work with, and going by this article, possibly even easier to implement sensibly?

(My main drivers are Emacs Calc on the computer and RealCalc on Android devices. For kitchen work I use a slide rule, which is something I think more people should do! There is nothing better for translating proportions.)

Reading this article and the thought process behind it reminds me of this almost-10-year-old comment I made about how they actually work: https://news.ycombinator.com/item?id=9456444

Selecting an operator loads this value into the accumulator and makes room for the second operand to be typed in.

Here is where I think the first mistake was made; if you observe the effect of repeatedly pressing '=', that obviously does not clear any registers, but merely repeats the last operation.

But there’s more to the story: it’s actually a side effect of a little-known “K-constant” feature that retains one of the previously-entered operands and the operator, and lets you vary the other operand.

I haven't used any 4-function calculator that behaves like this; instead, I get (without clearing):

    2 + 1 0 = 12
    5 =       22
    0 =       32

This article makes it sound more complicated than it is, collecting all those edge cases. Many of them can be simply ignored, as in being no-op. Which is also what most cheap calculators do...

I still wish to find the idiot who thought the reasonable thing to do when someone types 2 followed by SQRT is to return 2sqrt(

> Let’s start with the basics: the simplest calculator has ten digit keys, a decimal dot, four arithmetic operators (+, -, ×, ÷), a result button (“=”), and a “C” key to reset state.

Mathematically there is already quite a lot happening here and in addition (pun) we use base-10 representation of numbers, which is not the simplest.

Might be interesting to explore if decomposing the problem into even simpler "sub-calculators" (e.g., starting with binary addition) and then putting everything back together as a sort of progressive enhancement would reveal the most logical or economical UI.

"those cheap plastic rectangles hide decades of edge cases, quirks, and questionable design choices. Want to change a number's sign? That's a special case. Chain operations? Special case. Divide by pressing equals repeatedly? That's a feature called K-constant, except multiplication plays by different rules because... reasons. By the time you've handled every possible button combination, you'll wish you'd stuck to programming smart fridges"

I always found percent key behaviour to be such a bizarre choice.

Google's calculator on Android is an absolute shitshow. Sorry for omitting details, but this issue is easy for anyone to repro without any specific steps.

Oh, it doesn't even get to the juicy bit of percentages.

Can't remember how physical calculators deal with them, but software calculators deal with them differently.

To the point that iOS calc and MacOS calc are different. And variations of Windows calc (regular/scientific/engineering) are different

TL;DR PEDMAS is bullshit

If you look at the internal state of the typical physical calculate it's a beautifully simple machine that tries to catch the balance between RPN and logic... except it has stupid nonsensical human rules interjected.

So, every time this article where points out "actually it's more complicated than it seems" is where historically somebody has made deliberate design decisions to do it 'the dumb way' even though it adds complexity, to force something unnaturally.

And what you end up with is something that's half intuitive, it's in between the two systems, but it's more complicated than it needs to be.

Please, I would much prefer device for RPN calculation, that follows consistent logic, rather than silly imposed rules.

4+7*3 etc.

or 4 7 + 3 * =

Where the latter is much closer to what we do in our heads and conceptually think about it.