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John Carmack on mutable variables

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Re: John Carmack on mutable variables

#41

Post by brrrrrm »

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…

one thing I've learned in my career is that escape hatches are one of the most important things in tools made for building other stuff.

dropping down into the familiar or the simple or the dumb is so innately necessary in the building process. many things meant to be "pure" tend to also be restrictive in that regard.

Re: John Carmack on mutable variables

#44

Post by nielsbot »

hyperhello wrote: post #3

> I wish it was the default, and mutable was a keyword. I wish the IDE would simply provide a small clue, visible but graphically unobtrusive, that it was mutated . In fact, I end up wishing this about almost every language feature that passes my mind. For example, I don't need to choose whether I can or can't append to a list; just make it unappendable if you can prove I don't append. I don't care if it's a map, lis…

I use Swift for work. The compiler tell you this. If a mutable variable is never mutated it suggests making it non-mutable. And vice versa.

Re: John Carmack on mutable variables

#47

Post by runevault »

brrrrrm wrote: post #41
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…

one thing I've learned in my career is that escape hatches are one of the most important things in tools made for building other stuff. dropping down into the familiar or the simple or the dumb is so innately necessary in the building process. many things meant to be "pure" tend to also be restrictive in that regard.

Functional languages are not necessarily pure though. Actually outside Haskell don't most functional first languages include escape hatches? F# is the one I have the most experience with and it certainly does.

Re: John Carmack on mutable variables

#48

Post by johncolanduoni »

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…

I’ve done a significant amount of functional programming (including F#) and still reach for it sometimes, but I don’t think it provides substantial advantages for most use-cases. Local mutability is often clearer and more maintainable.

Also, category theorists think how excited people get about using the word monad but then most don’t learn any other similar patterns (except maybe functors) is super cringe. And I agree.

Re: John Carmack on mutable variables

#49

Post by stevage »

In JavaScript, I really like const and have adopted this approach. There are some annoying situations where it doesn't work though, to do with scoping. Particularly:

- if (x) { const y = true } else { const y = false } // y doesn't exist after the block - try { const x = foo } catch (e) { } // x doesn't exist after the try block

Re: John Carmack on mutable variables

#50

Post by NathanaelRea »

hyperhello wrote: post #3

> I wish it was the default, and mutable was a keyword. I wish the IDE would simply provide a small clue, visible but graphically unobtrusive, that it was mutated . In fact, I end up wishing this about almost every language feature that passes my mind. For example, I don't need to choose whether I can or can't append to a list; just make it unappendable if you can prove I don't append. I don't care if it's a map, lis…

I don't think this is the best option, there could be very hard bugs or performance cliffs. I think I'd rather have an explicit opt-in, rather than the abstraction changing underneath me. Have my IDE scream at me and make me consider if I really need the opt-in, or if I should restructure.

Although I do agree with the sentiment of choosing a construct and having it optimize if it can. Reminds me of a Rich Hickey talk about sets being unordered and lists being ordered, where if you want to specify a bag of non-duplicate unordered items you should always use a set to convey the meaning.

It's interesting that small hash sets are slower than small arrays, so it would be cool if the compiler could notice size or access patterns and optimize in those scenarios.

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