define introduces top-level values and functions.

Syntax

⟨monomorphize-directive⟩?
⟨inline-directive⟩?
⟨declare-directive⟩?
(define ⟨def⟩ ⟨docstring⟩? ⟨expr⟩)

;; ⟨def⟩ := ⟨name⟩
;;        | *⟨name⟩*
;;        | (⟨name⟩ ⟨arg⟩...)
;;
;; ⟨arg⟩ := ⟨name⟩
;;        | _
;;        | ⟨pattern⟩

Semantics

  • Defines a new value or function.
  • Type is automatically inferred, but a declare is recommended.
  • Can be inlined, monomorphized, or specialized.
  • Parameters which are not referenced can be named _ or _x where x can be any name.
  • If an argument is a data type with one constructor, a direct pattern match can be used.
  • The body of a function definition can return explicitly.
  • When ⟨name⟩ begins and ends with *, as in *base*, then define defines a dynamic variable. Otherwise, it defines an ordinary lexical variable.

Example

(define (add2 x)
  (+ x 2))

;; dynamic variable
(define *base* 10)