ludic/docs/language/list/list-swap.md

id	name	category	kind	tokens	sig	tip	order	ns	member
list-swap	List.swap	list	namespace-method	List.swap	List.swap(s, i, j) -> void	Exchange the elements at two indices.	6	List	swap

Exchanges the elements at indices i and j in s, in place. Both indices must be within the slice. Swapping is the building block of shuffles, sorts, and moving an item to the end before List.pop to remove it cheaply without shifting the rest.

Parameters:

• s — the slice to modify
• i — the first index
• j — the second index

program RemoveFast {
  state RemoveFastState {
    actors: []int = new []int
  }

  handler Kill(remove_fast_st: RemoveFastState) phase Update {
    let dead = 2
    let last = List.len(remove_fast_st.actors) - 1
    List.swap(remove_fast_st.actors, dead, last)   # move it to the end...
    let removed = List.pop(remove_fast_st.actors)  # ...then drop it
  }
}