cmp::Ordering vs comparison symbols
from alertsleeper@programming.dev to rust@programming.dev on 07 Jan 2024 21:31
https://programming.dev/post/8269174

beginner question: What is the advantage of using cmp::Ordering::Less over “<”, same for Greater and Equals?

#rust

sugar_in_your_tea@sh.itjust.works on 07 Jan 2024 21:40 next collapse

Here’s a good example.

Basically, cmp::Ordering::Less is an enum so a match using it is guaranteed to be exhaustive, whereas you need to be careful when doing an if/else chain that you cover all cases.

TehPers@beehaw.org on 08 Jan 2024 03:08 next collapse

What language? (I’m an idiot) If you’re referring to Rust, std::cmp::Ordering is an enum and can be used withPartialOrd/Ord to see how two values compare. The comparison operators basically call your partial_ord implementation. If you can use the operators themselves, use them instead of calling partial_ord in most cases.

In other languages, I don’t know, but I assume in general if you can use the operators, you should (unless you’re interested specifically in their ordering, not whether one is only one of greater than, equal to, or less than another).

luminasapphira@beehaw.org on 08 Jan 2024 03:54 collapse

I’m guessing you’re asking because you got a clippy lint. Using Ordering allows you to match the output therefore only calling partial_ord once, compared to using an if-else chain which might call it several times. In many/most cases this would probably be compiler optimized anyway but this makes it explicit.