Calling Functions

To call a function in Clojure you use the name of the function as the first element of a list.

In this simple example, a function is defined that takes no arguments, then that function is called.

(defn my-function []
  (str "I only return this string"))

(my-function)

Functions can be defined to take arguments.

Arity

This is the term to describe the number of arguments a function takes. This can be a fixed number or variable number of arguments.

Simple polymorphism can also be used to have one function take different numbers of arguments, as with the multi-arity function in the examples below.

(defn single-arity [] 
  (str "I do not take any arguments"))

(defn single-arity [argument] 
  (str "I take 1 argument only"))

(defn triple-arity [argument1 argument2 argument3] 
  (str "I take 3 arguments only"))

(defn multi-arity 
 ([argument] 
   (str "I match 1 argument only"))
 ([argument1 argument2]
   (str "I match when 2 arguments are used")))

(defn variable-arity [argument & more-arguments]
  (str "I assign the first argument to argument, 
        all other arguments to more-arguments"))