Atoms in

About Atoms

Since all of Clojure's standard data types are immutable, it offers reference types which offer controlled mutation. The simplest and most commonly used of these are called Atoms.

Atoms are created with the atom function, which take an initial value:

(def players (atom ()))

The current value of the atom is dereferenced with either deref or the @ shorthand:

@players
;;=> ()

The current value of the players atom can be modified using swap!, which updates the value by applying a function:

(swap! players conj :player1)
;;=> (:player1)

The reset! function replaces the value of an atom without regard for its current value:

(reset! players ())