completion-prefix-display-length
completion-prefix-display-length
Or the others.
But watchout if you try to pop nothing.
The rest of nothiing isn't so strict.
You can use vectors in clojure as an array like structure.
You can create a vector from a list.
Or from some elements.
But you can populate it with any number of elements at once.
Conjoining to a vector is different than conjoining to a list.
You can get the first element of a vector like so.
And the last in  similar fashion.
Or any index if you wish.
You can also slice a vector.
Equality of collections is in terms of values.