Macro for VecDeque

[sunjay]

Would it be possible to add a macro similar to vec! but for VecDeque instead?

[bluss]

Yeah, why not.

VecDeque::from(vec![1, 2, 3]) is not actually cost free, the conversion needs to realloc it to a power of two (which the vec's capacity is not necessarily). So the goal of the macro must be to be better than that somehow.

[sunjay]

Could the macro expand to use with_capacity() and push()?

[bluss]

Yes I think so. I guess using vec![] is sometimes more ideal, but users can then use that.

[sunjay]

This is the source for vec!: https://github.com/rust-lang/rust/blob/master/src/libcollections/macros.rs

If I'm understanding it correctly, it seems to be using some unstable features.

[bluss]

right, it's using the placement box stuff. It is really ideal to do it like that for vec![] but for vecdeque it makes an allocation that is (possibly) too small. Maybe I should look at the table of allocation size buckets again and see how they are spread.

[Nokel81]

I have an implementation based on with_capacity() and push_back(). Would a PR be welcome?

[Boscop]

@Nokel81 Yes, please :)

[Nokel81]

#31

[justin13888]

I know this thread has been open for a few years but wondering if this functionality was ever merged or should this issue still be open?

[gamedev-pnc]

What's status for this feature request?