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John Carmack on mutable variables

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Re: John Carmack on mutable variables

#31

Post by School-Cotton »

charcircuit wrote: post #27
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…

Const by default is not functional programming.

Indeed, but it's one of the (many) good ideas from functional programming that have filtered into more mainstream languages.

Re: John Carmack on mutable variables

#32

Post by kragen »

rapind wrote: post #26
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)…

> come with the baggage of foreign looking syntax Maybe they're right about the syntax too though? :)

Which one, Erlang, Lisp, or ML?

Re: John Carmack on mutable variables

#33

Post by loeg »

shmerl wrote: post #24

Proposing making immutable by default in C or C++ doesn't make sense due to backwards compatibility reasons. New languages like Rust have easier time making better choices with immutable by default.

cpp2/cfront could plausibly do this, right? Except he doesn't want to:

https://github.com/hsutter/cppfront/wiki/Design-note%3A-cons...

Re: John Carmack on mutable variables

#34

Post by turtletontine »

noduerme wrote: post #13

Why loops specifically? Why not conditionals? A lot of code needs to assemble a result set based on if/then or switch statements. Maybe you could add those in each step of a chain of inline functions, but what if you need to skip some of that logic in certain cases? It's often much more readable to start off with a null result and put your (relatively functional) code inside if/then blocks to clearly show different l…

There’s no mutating happening here, for example:

  if cond:
      X = “yes”
  else:
      X = “no”
X is only ever assigned once, it’s actually still purely functional. And in Rust or Lisp or other expression languages, you can do stuff like this:

  let X = if cond { “yes” } else { “no” };
That’s a lot nicer than a trinary operator!

Re: John Carmack on mutable variables

#37

Post by estimator7292 »

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…

Your IDE probably supports this as an explicit action. JetBrains has a feature that can find all reads and writes to a variable

Re: John Carmack on mutable variables

#40

Post by shmerl »

loeg wrote: post #33
shmerl wrote: post #24

Proposing making immutable by default in C or C++ doesn't make sense due to backwards compatibility reasons. New languages like Rust have easier time making better choices with immutable by default.

cpp2/cfront could plausibly do this, right? Except he doesn't want to: https://github.com/hsutter/cppfront/wiki/Design-note%3A-cons...

Well, if they are willing to break backwards compatibility, a lot of things can be improved, including this.
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