;;;; unless, which used to be a special form in parse.ml and is a defmacro in
;;;; the prelude now. plan.org milestone 5 says the five conditional sugars are
;;;; special forms only until macros land; this is the first one to stop being
;;;; one, and running this file means the expander compiled a macro into a
;;;; shared object, dlopened it into the compiler, and called it -- before the
;;;; first line below was parsed.
;;;;
;;;; Nothing here is new syntax. Every line of it compiled the same way before
;;;; the move, which is the point: the test for the feature is the corpus that
;;;; was written against the special form.

(defn classify [n i32] string
  (let [out "even"]
    (unless (= 0 (% n 2))
      (set out "odd"))
    out))

(defn main [] i32
  ;; One body form, the common case.
  (unless false (println "the test was false"))
  (unless true (println "NOT PRINTED"))

  ;; Several, which is what the do in the expansion is for.
  (unless false
    (print "a")
    (print "b")
    (println "c"))

  ;; A computed test, so the argument is a form the macro had to put back
  ;; rather than a literal it could have ignored.
  (let [n 7]
    (unless (< n 3) (println "7 is not less than 3")))

  ;; Inside a function that returns a value, and inside a loop: the expansion
  ;; is an if with no else, so it is () and it does not decide the body's
  ;; value.
  (println (classify 4))
  (println (classify 5))

  (let [seen 0]
    (dotimes [i 5]
      (unless (= i 2) (set seen (+ seen 1))))
    (print seen) (println ""))
  0)