path: root/fnl/curry.fnl

;; see <https://wiki.fennel-lang.org/Currying> for details

(fn curry [f n ?args]
  (let [args (or ?args {:n 0})]
    (fn [...]
      (let [inner (table.pack ...)
            n* (+ args.n inner.n)]
        (doto inner
          (table.move 1 inner.n (+ args.n 1))
          (tset :n n*))
        (table.move args 1 args.n 1 inner)
        (if (>= n* n)
            (f ((or _G.unpack table.unpack) inner 1 n*))
            (curry f n inner))))))

(macro defcurry [name arglist ...]
  `(local ,name
     (curry (fn ,arglist ,...)
            ,(length (icollect [_ a (ipairs arglist)
                                :until (= (tostring a) "...")]
                       a)))))