Variables

Global variables can be defined with (define):

(define x 5)

Functions can also be defined that way, but you can also use the (def) macro:

(define f
  (fn (x)
    x))

(def (f x)
  x)

(define) always defines things in the global environment. To define local variables, you can use (let):

(let x (get-value)
  (print x))

Once defined, variables can be modified with the low level (set-symbol), or the (set) macro:

(let x (get-value)
  (set x (get-other-value))
  (print x))

(define a-list '())
(set-symbol 'a-list (cons 5 a-list))

The (set) macro can also be used to modify properties:

(define d (dict))
(set (at d "key") "value")
(print (at d "key"))
; value

Internally, (set) rewrites (set (f ...) v) forms to (g ... v), where g is a pre-defined setter in the global setter-store dictionary. In this case, 'at is associated with 'set-at in the dictionary, so (set) will rewrite (set (at d "key") value) to (set-at d "key").

Note: the (unset) function can be used to remove global definitions. However, using it is not recommended as it can break things that depend on the definitions you remove.