Add as_slice methods to DenseSlotMap.

[orlp]

Supersedes #134.

Fixes #131.

Credit to @Swiiz for the examples.

[jagprog5]

@orlp this is missing critical functionality. see my MR. sure, I understand now allowing mutable slice to keys, that's fine. but there should still be both [ immutable keys slice, and mutable values slice] provided as output together.

this is required by ets. current exposed API makes it impossible to satisfy borrow checker - need explicit disjoint borrow

[orlp]

Hmm I see. I also just noticed that in my earlier discussion I wanted to add as_slices and as_mut_slices.

I think I'll add these two and probably remove the other *_as_slice variants in 2.0 again.

[orlp]

@jagprog5 Fixed in 1.1.1.

[melody-rs]

From what I can see this is missing a way to go from key -> value index?

[jagprog5]

From what I can see this is missing a way to go from key -> value index?

@melody-rs not sure what you mean; the keys and values are in the same arbitrary order so key[i] goes to value[i]

[melody-rs]

From what I can see this is missing a way to go from key -> value index?

@melody-rs not sure what you mean; the keys and values are in the same arbitrary order so key[i] goes to value

Sorry, could've explained better!
I meant that there's no way to do:

use slotmap::*;
let mut sm = DenseSlotMap::new();
let key = sm.insert(0i32);
let values = sm.values_as_slice();
let value_index = /* get the index of the value in the slice */
let value = values[value_index];
assert_eq!(value, sm[key]);

Being able to get the index is useful for copying a DenseSlotMap into a GPU buffer since you can use the index associated with a key to look up something in a shader

[jagprog5]

@melody-rs I don't think this is possible since the index isn't stable; it will re-order to compact to contiguous memory if elements are deleted.

If you're using the dense slot map and only inserting, then you could use an incrementing counter? double check this. So first insertion is at slice index 0, next one at index 1, ...