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But then you realise that the types of 10 constituent fields don’t implement Eq, PartialEq…
I do appreciate how newer C++ standards have made these kinds of things a lot easier too.
Define all comparison operators with just one one line using C++20
auto operator<=>(const ClassName&) const = default;It’s nice that this exists these days, but my god is it horrendously unreadable at a glance
That is completely incomprehensible lol
BuT ItS uNsAfE.
Only if you’re a bad programmer :/
This argument just doesn’t hold up. Software written by some of the best developers in the world still has these same bugs.
Why even use a language where you have to put so much effort into something that comes for free in many modern languages.
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)?
Yes, it is that simple. In Rust if you have a structure
Personand 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,
PartialEqandEqare traits, which are similar to interfaces in Java. Manually implementing thePartialEqtrait in this example would be writing code that returns something likea.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
Cloneto allow creating a copy of an instance,Debugfor getting a string representation of an object, andPartialOrdandOrdfor 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.It’s because people put in the hard work of writing amazing macros instead of baking code reuse into the type system itself 😁 I’m a rust noob and I love the derive macro.
So it’s actually a secret third option! That’s pretty rad.
Derive macros are a godsend. There’s macros to automatically implement serialization as well. Basically a Trait that can automatically be implemented when derived
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
Equality in rust is value equality per default, that’s what these traits are for. If you want to check pointer equality you’d use the
std::ptr::eqfunction to check if two pointers are equal, which is rather rare in practice. You can also implement thePartialEqtrait yourself if you need custom equality checks.
Haskell:
deriving EqI’ve only had to implement equality in C# but that didn’t seem that hard of a problem. you just expand the operator = function
Then you should also override
Equals(object),GetHashCode, and implementIEquatable<T>.Thankfully a lot of the usual boilerplate code can be avoided using a
recordclass or struct:public record Person(string Name, uint Age);It’s not hard, just if you’re doing it for a struct with a lot of fields it’s a lot of boilerplate
My IDE can do that for me. And it was able to do that pre AI boom. Yes, the code ends up more verbose, but I just collapse it.
So from a modern dev UX perspective, this shouldn’t be a major difference.
I just use the HashCode class and compare the results.
Pretty sure there’s a source generator for it as well nowadays.
