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Inline const expressions have been stabilised (github.com)

submitted 5 months ago by [email protected] to c/[email protected]

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[–] [email protected] 5 points 5 months ago (3 children)

Huh, this is awesome! From the link, this now works:

let v: Vec<i32> = const { Vec::new() };

I'm going to have to play with this to see how far it goes.

[–] [email protected] 2 points 5 months ago (1 children)

Wouldn't this just prevent you from allocating more memory (than zero)?

[–] [email protected] 2 points 5 months ago* (last edited 5 months ago)

Ah, apparently for now you're not allowed to allocate. But vec::new_in(allocator) looks interesting. This works in nightly today:

#![feature(allocator_api)]

use std::alloc::Global;

fn main() {
    const MY_VEC: Vec<i32> = const {
        Vec::new_in(Global)
    };
    println!("{:?}", MY_VEC);
}

Maybe at some point I can append to it at compile time too. I'd love to be able to put a const {} and have allocations that resolve down to a 'static, and this seems to be a step toward that.

I guess I'm just excited that Vec::new() is the example they picked, since the next obvious question is, "can I push?"

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