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The C++ standard for the F-35 Fighter Jet [video]

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327 points AareyBaba | 4 comments | 07 Dec 25 18:07 UTC | HN request time: 0s | source
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don-code ◴[07 Dec 25 23:11 UTC] No.46186343[source]▶
> All if, else if constructs will contain either a final else clause or a comment indicating why a final else clause is not necessary.

I actually do this as well, but in addition I log out a message like, "value was neither found nor not found. This should never happen."

This is incredibly useful for debugging. When code is running at scale, nonzero probability events happen all the time, and being able to immediately understand what happened - even if I don't understand why - has been very valuable to me.

replies(2): >>46187141 #>>46187743 #
kace91 ◴[08 Dec 25 01:00 UTC] No.46187141[source]▶
I like rust matching for this reason: You need to cover all branches.

In fact, not using a default (the else clause equivalent) is ideal if you can explicitly cover all cases, because then if the possibilities expand (say a new value in an enum) you’ll be annoyed by the compiler to cover the new case, which might otherwise slip by.

replies(1): >>46190383 #
1. uecker ◴[08 Dec 25 09:49 UTC] No.46190383[source]▶
And I like using enums in C ;-) The compiler tells you to cover all branches.

https://godbolt.org/z/bY1P9Kx7n

replies(2): >>46191651 #>>46192254 #
2. rundev ◴[08 Dec 25 12:52 UTC] No.46191651[source]▶
The compiler also tells you that even if you cover all enum members, you still need a `default` to cover everything, because C enums allow non-member values.
3. kace91 ◴[08 Dec 25 13:55 UTC] No.46192254[source]▶
Rust is a bit smarter than that, in that it covers exhaustiveness of possible states, for more than just enums:

fn g(x: u8) { match x { 0..=10 => {}, 20..=200 => {},

    }
}

That for example would complain about the ranges 11 to 19 and 201 to 255 not being covered.

You could try to map ranges to enum values, but then nobody would guarantee that you covered the whole range while mapping to enums so you’d be moving the problem to a different location.

Rust approach is not flawless, larger data types like i32 or floats can’t check full coverage (I suppose for performance reasons) but still quite useful.

replies(1): >>46192698 #
4. uecker ◴[08 Dec 25 14:37 UTC] No.46192698[source]▶
In principle C compilers can do this too https://godbolt.org/z/Ev4berx8d although you need to trick them to do this for you. This could certainly be improved.