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John Carmack on mutable variables

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498 points azhenley | 1 comments | 31 Oct 25 02:34 UTC | HN request time: 0s | source
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munchler ◴[31 Oct 25 02:54 UTC] No.45767832[source]▶
> 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 F# for starters. I switched and never looked back.

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tasn ◴[31 Oct 25 03:05 UTC] No.45767898[source]▶
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), so a pure first approach ends up being weird for many people.

At least based on my experience.

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rapind ◴[31 Oct 25 03:31 UTC] No.45768098[source]▶
> come with the baggage of foreign looking syntax

Maybe they're right about the syntax too though? :)

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kragen ◴[31 Oct 25 03:37 UTC] No.45768148[source]▶
Which one, Erlang, Lisp, or ML?
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tmtvl ◴[31 Oct 25 09:47 UTC] No.45770119[source]▶
Lisp syntax is objectively superior because you can write a predicate like thus:

  (< lower-bound x-coordinate upper-bound)
Instead of having to do the awful ampersand dance.
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1. kragen ◴[31 Oct 25 15:37 UTC] No.45773270[source]▶
In Python or Icon (or Unicon) that's

    lower_bound < x_coordinate < upper_bound
except that usually you want

    lower_bound <= x_coordinate < upper_bound
which is also legal.

In Python this is a magical special case, but in Icon/Unicon it falls out somewhat naturally from the language semantics; comparisons don't return Boolean values, but rather fail (returning no value) or succeed (returning a usually unused value which is chosen to be, IIRC, the right-hand operand).

And in SQL you have

    `x-coordinate` between `lower-bound` - 1 and `upper-bound` + 1
which is obviously the best possible syntax.