;; @module defkey.lsp
;; @description An attempt to add keyword arguments to functions

;; @example
;; (defkey (f a (b 20) c) (list a b c))
;; (f 10 :c 30) => (10 20 30)

(define-macro (defkey header)
  (let (_makedef (fn (_x) (if (symbol? _x)
                            (list _x nil)
                            (list (_x 0) (eval (_x 1))))))
    (letex ((Name (header 0))
            (Default (map _makedef (1 header)))
            (Body (cons 'begin (args))))
      (define-macro (Name)
        (letn ((_default 'Default)
               (_arglist (args))
               (_offset-nil (find ': _arglist))
               (_offset-len (or _offset-nil (length _arglist)))
               (_pos-default (0 _offset-len _default))
               (_pos-arglist (0 _offset-len _arglist))
               (_key-arglist (_offset-len _arglist)))
          (map set (map first _default) (map last _default))
          (map set (map first _pos-default) (map eval _pos-arglist))
          (if (!= (% (length _key-arglist) 3) 0) (throw 'error))
          (dolist (_triple (explode _key-arglist 3))
            (local (_tag _key _val)
              (map set '(_tag _key _val) _triple)
              (if (!= _tag ':) (throw error))
              (set _key (eval _val))))
          Body)))))