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John Carmack on mutable variables

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Re: John Carmack on mutable variables

#301

Post by furyofantares »

AaronAPU wrote: post #267

This would require coming up with an order of magnitude more variable names which is just unnecessary cognitive load.

An order of magnitude? That sounds like pretty outrageous hyperbole. A variable getting reassigned 10 times sounds extremely rare, the average in my experience has to be less than 1 reassignment. I think the approach requires coming up with maybe 10% more names.

Usually there are good, obvious names for intermediate calculations in my experience.

I'm open though - what kinds of things are you doing that require reassigning variables so much?

Re: John Carmack on mutable variables

#302

Post by Tarean »

rendaw wrote: post #188
EastLondonCoder wrote: post #128

After a 2 year Clojure stint I find it very hard to explain the clarity that comes with immutability for programmers used to trigger effects with a mutation. I think it may be one of those things you have to see in order to understand.

I think the explanation is: When you mutate variables it implicitly creates an ordering dependency - later uses of the variable rely on previous mutations. However, this is an implicit dependency that isn't modeled by the language so reordering won't cause any errors. With a very basic concrete example: x = 7 x = x + 3 x = x / 2 Vs x = 7 x1 = x + 3 x2 = x1 / 2 Reordering the first will have no error, but you'll get t…

Sometimes keeping a fixed shape for the variable context across the computation can make it easier to reason about invariants, though.

Like, if you have a constraint is_even(x) that's really easy to check in your head with some informal Floyd-Hoare logic.

And it scales to extracting code into helper functions and multiple variables. If you must track which set of variables form one context x1+y1, x2+y2, etc I find it much harder to check the invariants in my head.

These 'fixed state shape' situations are where I'd grab a state monad in Haskell and start thinking top-down in terms of actions+invariants.

Re: John Carmack on mutable variables

#303

Post by Razengan »

veltas wrote: post #243
Razengan wrote: post #145

If designing your hypothetical ideal language, what are some intuitive/cute keywords you would choose for mutables/immutables? `let` is so 2020. `const` is too long. `static` makes me fall asleep at the keyboard. `con` sounds bad. How about `law`? law pi = 3.142 (heh typing on Mac autocompleted this) law c = 29979245 law law = "Dredd" or `set` or `once` or `make`?

What is wrong with let?

Nothing, it's just been done, just trying to think of some better/newer ways to say it :)

Re: John Carmack on mutable variables

#304

Post by danenania »

munchler wrote: post #2

> Making almost every variable const at initialization is good practice. I wish it was the default, and mutable was a keyword. It's funny how functional programming is slowly becoming the best practice for modern code (pure functions, no side-effects), yet functional programming languages are still considered fringe tech for some reason. If you want a language where const is the default and mutable is a keyword, try…

It’s because FP, great as it is, is most beneficial when 80/20’d.

Trying to do it 100% pure makes everything take significantly longer to build and also makes performance difficult when you need it. It’s also hard to hire/onboard people who can grok it.

Re: John Carmack on mutable variables

#306

Post by TheRoque »

I also default to const in javascript. Somehow a "let" variable feels so dirty, but I don't really know why. I guess at this point my experience forged an instinct but I can't even put a theory on it. But it's sometimes necessary and I use it of course.

Re: John Carmack on mutable variables

#307

Post by mr_luc »

acdbddh wrote: post #299

In python its common to see code like this: df = pd.concat(df,other_df) df = df.select(...) ... My eyes hurts, when I see it. It makes me avoid python. I bet the reason for this mutable code is a missing simple pipes syntax. I love pipes. In R can do: df |> rbind(other_df) |> select(...) It feels much better.

Elixir too (Explorer library; default backend is Pola.rs based)

- https://github.com/elixir-explorer/explorer - https://hexdocs.pm/explorer/Explorer.html

Re: John Carmack on mutable variables

#308

Post by dragonwriter »

tasn wrote: post #10
munchler wrote: post #2

> Making almost every variable const at initialization is good practice. I wish it was the default, and mutable was a keyword. It's funny how functional programming is slowly becoming the best practice for modern code (pure functions, no side-effects), yet functional programming languages are still considered fringe tech for some reason. If you want a language where const is the default and mutable is a keyword, try…

Functional programming languages (almost always?) come with the baggage of foreign looking syntax. Additionally, imperative is easier in some situations, so having that escape hatch is great. I think that's why we're seeing a lot of what you're describing. E.g. with Rust you end up writing mostly functional code with a bit of imperative mixed in. Additional, most software is not pure (human input, disk, network, etc)…

> Functional programming languages (almost always?) come with the baggage of foreign looking syntax.

That increases the activation energy, I guess, for people who have spent their whole programming life inside the algol-derived syntax set of languages, but that’s a box worth getting out of independently of the value of functional programming.

Re: John Carmack on mutable variables

#309

Post by pacoverdi »

xxs wrote: post #263
throwaway2037 wrote: post #113

Earlier quoted context omitted.

In my IntelliJ (a recent version), if I write a small Java function like this: private static void blah() { final int abc = 3; for (int def = 7; def The variable 'def' is underlined. Mouse-over hint shows: 'Reassigned local variable'. To be clear, 'abc' is not underlined. When I write Java, I try to use the smallest variable scopes possible with as much final (keyword) as possible. It helps me to write more maintaina…

1st) you use ++def in a loop, don't be weird; 2nd) if 'abc' is to be used in the loop body, define in the loop, e.g. for (int def = 7, abc =3; ...); 3rd) this is an IntelliJ bug - both 'def' and 'abc' in the sample are always defined.

3) looks like you read 'underlined' as 'undefined'

Re: John Carmack on mutable variables

#310

Post by nixpulvis »

furyofantares wrote: post #291
nixpulvis wrote: post #282

I try to keep deeper mutation to where it belongs, but I'll admit to shadowing variables pretty often. If I have a `result` and I need to post-process it. I'm generally much happier doing `result = result.process()` rather than having something like `preresult`. Works nicely in cases where you end up moving it into a condition, or commenting it out to test an assumption while developing. If there's an obvious name fo…

You're using really generic terms which I have to think is mostly because you're talking about it in the abstract. In most scenarios I find there are obvious non-generic names I can use for each step of a calculation.

I mean, I use `result` in a function named `generate` within a class `JSON < Generator`. Stuff like this is pretty common.
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