Prepending to a list is easy:
user=> (conj '(:bar :baz) :foo)
(:foo :bar :baz)
Appending to a vector is easy:
user=> (conj [:bar :baz] :foo)
[:bar :baz :foo]
How do I (idiomatically) prepend to a vector, while getting back a vector?
This does not work as it returns a seq, not a vector:
user=> (cons :foo [:bar :baz])
(:foo :bar :baz)
This is ugly (IMVHO):
user=> (apply vector (cons :foo [:bar :baz]))
[:foo :bar :baz]
Note: I basically just want a datastructure that I can append and prepend to. Appending to large lists should have a large performance penalty, so I thought of vectors..
Vectors are not designed for prepending. You have only O(n) prepend:
What you want is most likely a finger tree.