variables-and-functions.md

Variables and Functions

(def foo 0)

This will define a variable in the current module named foo to the value 0. def will also overwrite the closest variable of the same name, so it can change the value of a function argument or a let binding value as well.

Defining Functions

A function literal can be created with the fn form:

(fn (x y)
  (+ x y))

This creates a function literal which when called with 2 arguments, returns their sum. You can define a variable to a function as,

(def add (fn (x y)
            (+ x y)))

But this is a little bit too much to type every time for something thats important as a function binding, so there's a macro for that (and an overloaded def):

;; All these things do the same exact thing:
(def add (fn (x y)
            (+ x y)))
(defn add (x y)
   (+ x y))
;; The overloaded def syntax...
(def (add x y)
   (+ x y))

I'm particularly a fan of the overloaded def syntax because the funciton signature represents the calling syntax. You would call add with (add 1 2) which looks alot like the signature when you define it.

You'll also notice that there is no type information in functions.