Comment by MangoToupe
8 hours ago
> As another commenter wrote "how do you allocate memory without an allocator?"
You call these things something other than an "allocating" and "allocators". Seriously, few people would consider adding a value to a hashmap an intentionally allocational activity, but it is. Same with adding an element to a vector, or any of the dependent actions on it.
Seriously
For "adding an element to a vector" it's actually not necessarily what you meant here and in some contexts it makes sense to be explicit about whether to allocate.
Rust's Vec::push may grow the Vec, so it has amortized O(1) and might allocate.
However Vec::push_within_capacity never grows the Vec, it is unamortized O(1) and never allocates. If our value wouldn't fit we get the value back instead.