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John Carmack on mutable variables

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Re: John Carmack on mutable variables

#311

Post by dionian »

rao-v wrote: post #84
tasn wrote: post #10

Earlier quoted context omitted.

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)…

Exactly this! I’d love a modern C++ like syntax with the expressiveness of python and a mostly functional approach. C# is not that far I suppose from what I want

Scala

Re: John Carmack on mutable variables

#312

Post by dionian »

gf000 wrote: post #136
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 you want a tasteful mix of both. I believe Scala was pretty ahead here by building the language around local mutability with a general preference for immutable APIs, and I think this same philosophy shows up pretty strongly in Rust, aided by the borrow checker that sort of makes this locality compiler-enforced (also, interior mutability)

Worth nothing that idiomatic scala uses constants by default, variables are discouraged and frankly rare.

Re: John Carmack on mutable variables

#313

Post by fermisea »

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.

pandas has a .pipe operator which works exactly like this

Re: John Carmack on mutable variables

#314

Post by dionian »

Razengan wrote: post #179
tomaytotomato wrote: post #147

Earlier quoted context omitted.

There was a proposal in Java a few years back to introduce "val". I think it never gained traction but it would have been nice to have this in Java val firstName = "Bob"; val lastName = "Tables"; var fullName = ""; fullName = firstName + " " + lastName;

That's an aesthetically awkward and also bug-prone syntax: So just a difference of 1 single letter (that looks similar) to mean the completely opposite thing?? Nah you don't want that, and I don't either.

They're intuitively named. A value is a value. A variable is a variable.

Re: John Carmack on mutable variables

#315

Post by everforward »

a4isms wrote: post #223
Thorrez wrote: post #211

Earlier quoted context omitted.

Immutable and constant are the same. rendaw didn't use the word mutable. One reason someone might use the word "mutable" is that it's a succinct way of expressing an idea. Alternative ways of expressing the same idea are longer words (changeable, non-constant).

In languages like JavaScript, immutable and constant may be theoretically the same thing, but in practice "const" means a variable cannot be reassigned, while "immutable" means a value cannot be mutated in place. They are very, very different semantically, because const is always local. Declaring something const has no effect on what happens with the value bound to a const variable anywhere else in the program. Where…

Arrays are a very notable example here. You can append to a const array in JS and TS, even in the same scope it was declared const.

That’s always felt very odd to me.

Re: John Carmack on mutable variables

#316

Post by throwaway_7274 »

anymouse123456 wrote: post #283

I completely agree with the assertion and the benefits that ensue, but my attention is always snagged by the nomenclature. I know there are alternate names available to us, but even in the context of this very conversation (and headline), the thing is being called a "variable." What is a "variable" if not something that varies?

Right, yeah, it’s a funny piece of terminology! The sense in which a ‘variable’ ‘varies’ isn’t that its value changes in time, but that its value is context-dependent. This is the same sense of the word as used in math!

Re: John Carmack on mutable variables

#317

Post by xxs »

pacoverdi wrote: post #309
xxs wrote: post #263

Earlier quoted context omitted.

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'

true that, thanks!

Re: John Carmack on mutable variables

#318

Post by philipov »

nixpulvis wrote: post #310
furyofantares wrote: post #291

Earlier quoted context omitted.

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.

if you're already committing to generic names, what's wrong with a name like `processed_result`?

Re: John Carmack on mutable variables

#319

Post by TheAceOfHearts »

jpgvm wrote: post #261
villgax wrote: post #165

Earlier quoted context omitted.

Just like AGI he was supposedly brought on board for but…..checks notes. Nothing.

Dude isn't a god. That said it's worth listening when he chimes in about C/C++ or optimisation as he has earned his respect when it comes to these fields. Will he crack AGI? Probably not. He didn't crack rockets either. Doesn't make him any less awesome, just makes him human.

There are certain figures who are very experienced and knowledgeable in certain domains, so when they speak up about a topic it's usually worth listening to them. That doesn't mean they're always going to be correct, and they shouldn't be worshiped as superhuman entities, but it's almost always a bad idea to completely ignore them.

Re: John Carmack on mutable variables

#320

Post by snarfy »

philipov wrote: post #318
nixpulvis wrote: post #310

Earlier quoted context omitted.

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

if you're already committing to generic names, what's wrong with a name like `processed_result`?

In the flow he describes you end up with processed_processed_processed_result.
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