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Comment by gf000 | Hacker News Reader

Just putting it out here - before the recentish redesign of ios's default calculator, it had a widely non-intuitive behavior. Due to how it looked I assumed it works as a standard four-function calculator, but it was actually storing the whole expression in memory and executing it as per the standard precedence rules.

I do usually prefer the latter behavior, but without it being displayed as in more advanced calculators (it has been changed to show it) it's just not what I would expect at all, resulting in wrong calculations. But maybe it was just a "me-problem".

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When I used to teach math, the difference in how calculators handled precedence was always a problem. I would tell students to enter 1+2×3 into their calculators and if they got 9,¹ they should throw away the calculator and buy one that worked properly. Not respecting the precedence rules is bad design.

The calculator built into Windows (at least back then, maybe they’ve changed it), gave 9 to my test instead of 7.

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1. If they got some number other than 9 or 7, I recommended dousing it in holy water, and then gasoline, burning it, encasing the ashes in concrete and dropping that concrete block into the deepest part of the ocean because that calculator is cursed.

Not respecting precedence is ok, as long as the user is aware of it.

When I use a calculator, I don't necessarily care if I can punch in a written expression verbatim from left to right. I just want to do a calculation.

Except that if you’re a high school student who is using a calculator for stuff most if not all of the readers on this site would do in your head, having a calculator that ignores precedence just makes things that much harder.

A high school student should already know the difference between a dumb calculator that can only show a single number and a smart calculator that lets you to write a full line while using () before pressing =, having used both already by middle school.

just tested this. in "standard" mode you get 7, switch to "scientific" you get 9.

These "four-function" calculators only display the last number. It would be widely unexpected if doing x3 when all I see is a 2 would sometimes give 6 or some other value (e.g. the student next to me just passed a calculator with a value displayed, so I don't know if it had any previous instructions and no way to find out)

The UX is pretty clear - it's ANS operator newNumber. That's it, if not somehow displayed, then it shouldn't have a more complicated model inside either.

It can freely do "normal" math the moment they write out the whole expression tree, as the result of an expression is the one calculated by precedence rules. The result of a two-operand operation is not that, though.

You’re right it was terrible for a while. I’m glad they fixed it.

>Due to how it looked I assumed it works as a standard four-function calculator, but it was actually storing the whole expression in memory and executing it as per the standard precedence rules.

Isn't that how even fairly cheap 'real' calculators do it now though or do really cheap ones really just do one operation at a time from left to right?

I would have assumed that cheap (i.e. 4-function, LCD) calculators today have the same internals as cheap calculators from the 1980s. Why reinvent what works, when you can just keep selling it.

Why would you assume iOS, not being the cheap option for a smartphone, would choose to emulate a cheap calculator?

There were non-cheap calculators in the 1980s, too, that did proper evaluation. The ones I remember had keys for parentheses, though, allowing you to enter, for example

  (3 + 4) * 7 =

to get 49.

For an example see the TI-25 at http://www.datamath.org/Sci/Slimline/TI-25.htm

Well I was responding to a post about "really cheap calculators" not non-cheap ones or iOS ones.

The point is, precedence following expression evaluation calculators starting from the 80s have always shown you the expression. No expression and no parentheses buttons (accumulator stack) implies a simple accumulator based design.

The app did have parentheses buttons, depending on rotation you’d get simple or scientific UI.

Rotation changing how the calendar handled order of operations seems even less intuitive to me.

> Why would you assume iOS, not being the cheap option for a smartphone, would choose to emulate a cheap calculator?

i'd assume that because the ui for the ios calculator app is the same as the ui of a cheap calculator. not sure i would ever consider the platform that app is running on.

> ui for the ios calculator app is the same as the ui of a cheap calculator.

Rotate it and the app was a basic scientific calculator.

One of first things I do when I set up a new iThing is to delete the calculator app and install a third-party calculator.

I've been RPN for so long that I pretty much need an RPN calculator app even for relatively simple stuff.

I didn’t start using RPN until many years after graduating college, but took to it like a fish to water. I never again have to guess what the calculator might be doing behind the scenes. It’s doing exactly what I told it, no more or less, in precisely the order I told it.

When I started college, HPs were still really expensive so I got a TI which still wasn’t cheap. But calculator prices were plummeting like a stone and got a (relative) deal on a HP-55 a year or two later.

this is me too. I literally can't use a regular calculator anymore and I'm not even doing fancy math. my brain was just permanently rewired by the HP-12c

I’ve been using PCalc, since last century (it does have an RPN mode).

https://pcalc.com/

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