Question about ordered remove

[tspiteri]

I wanted to remove an element without perturbing the order of the remaining elements, and used something like the code below. Is there a better way than this? (In my case it is not really that important, this works just fine for me.)

type Map = IndexMap<K, V>;
fn remove_ordered(m: &mut Map, key: &K) -> Option<V> {
    let (index, _key, val) = m.swap_remove_full(key)?;
    if index < m.len() {
        let tail = m.len() - index - 1;
        let mut stack = Vec::with_capacity(tail);
        for _ in 0..tail {
            stack.push(m.pop().expect("disappearing elements"));
        }
        let (last_key, last_val) = m.pop().expect("disappearing elements");
        m.extend(stack.into_iter().rev());
        m.insert(last_key, last_val);
    }
    Some(val)
}

[cuviper]

without perturbing the order of the remaining elements

Just to be clear, the relative order is preserved, but the indexes of all entries after the removed one will be shifted. Doing otherwise would require leaving a hole, which we decided against.

I think we should add an ordered remove method though. Within the crate, we should be able to fixup the trailing items without rehashing them, so it will be faster that what you have. I suggest we deprecate remove, as that just calls swap_remove, and then add a distinct ordered_remove or some such.

[dbeckwith]

Having an order-preserving remove is all that's stopping me from using this crate right now, would be perfect if that gets added!

[KabDeveloper]

@cuviper Hi,

Do order-preserving remove feature already added or not yet please ?

If not, is there any faster alternative function to preserve the orders ?