(pop coll)
For a list or queue, returns a new list/queue without the first item, for a vector, returns a new vector without the last item. If the collection is empty, throws an exception. Note - not the same as next/butlast.
user=> (peek [1 2 3])
3
user=> (pop [1 2 3])
[1 2]
user=> (peek '(1 2 3))
1
user=> (pop '(1 2 3))
(2 3)
user=> (peek ())
nil
user=> (pop ())
IllegalStateException Can't pop empty list
user=> (peek [])
nil
user=> (pop [])
IllegalStateException Can't pop empty vector