this post was submitted on 15 Nov 2024
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[–] Ashelyn@lemmy.blahaj.zone 18 points 1 day ago (2 children)

Is that because it's that simple, or just that the boilerplate is pre-written in the standard library (or whatever it's called in rust)?

[–] rustyfemboy@lemmy.blahaj.zone 20 points 1 day ago

Yes, it is that simple. In Rust if you have a structure Person and you want to allow testing equality between instances, you just add that bit of code before the struct definition as follows:

#[derive(PartialEq, Eq)]
struct Person {
    name: String,
    age: u32,
}

In Rust, PartialEq and Eq are traits, which are similar to interfaces in Java. Manually implementing the PartialEq trait in this example would be writing code that returns something like a.name == b.name && a.age == b.age. This is pretty simple but with large data structures it can be a lot of boilerplate.

There also exist other traits such as Clone to allow creating a copy of an instance, Debug for getting a string representation of an object, and PartialOrd and Ord for providing an ordering. Each of these traits can be automatically implemented for a struct by adding #[derive(PartialEq, Eq, Clone, Debug, PartialOrd, Ord)] before it.

[–] Dhs92@programming.dev 16 points 1 day ago (1 children)

Derive macros are a godsend. There's macros to automatically implement serialization as well. Basically a Trait that can automatically be implemented when derived

[–] Dunstabzugshaubitze@feddit.org 6 points 1 day ago (1 children)

i've only read about rust, but is there a way to influence those automatic implementations?

equality for example could be that somethings literally point to the same thing in memory, or it could be that two structs have only values that are equal to each other

[–] 2xsaiko@discuss.tchncs.de 1 points 1 day ago

Not for the built-in Eq derive macro. But you can write your own derive macros that do allow you to take options, yeah.