* TODO =assert_equal_type= macro in testing
* DONE use an enum for builtin identifiers
  CLOSED: [2018-10-11 Do 17:15]
* TODO dont create new nils or builtins, but store one of each globally
* TODO source code locations for errors
* Build-in forms

** DONE +
   CLOSED: [2018-09-18 Di 12:14]
** DONE -
   CLOSED: [2018-09-18 Di 12:14]
** DONE *
   CLOSED: [2018-09-18 Di 12:14]
** DONE /
   CLOSED: [2018-09-18 Di 12:14]
** TODO >
** TODO <
** TODO =

** DONE if
   CLOSED: [2018-09-18 Di 12:14]
** DONE and (short circuiting)
   CLOSED: [2018-10-05 Fr 22:21]
** DONE or
   CLOSED: [2018-10-05 Fr 22:21]
** DONE not
   CLOSED: [2018-10-05 Fr 22:21]
#+begin_src emacs-lisp
(not 1)                  ;; == (not . (1 . nil))
(not (expression 1 3))   ;; == (not . ((expression . (1 . (3 . nil))) . nil))
(not)                    ;; == (not . nil)
(not 1 2)                ;; == (not . (1 . (2 . nil)))
#+end_src

#+RESULTS:
: t

** DONE first  (car)
   CLOSED: [2018-10-08 Mo 20:28]
** DONE rest   (cdr)
   CLOSED: [2018-10-08 Mo 20:28]
** DONE pair   (cons)
   CLOSED: [2018-10-08 Mo 20:28]

** TODO load   (import)
** DONE define
   CLOSED: [2018-10-08 Mo 20:28]
** TODO lambda
** TODO progn
** DONE eval
   CLOSED: [2018-10-08 Mo 20:28]

(setq condition (quote (= a 10)))
(setq a 10)
(eval condition)
(setq a 11)
(eval condition)

** DONE quote
   CLOSED: [2018-10-08 Mo 20:28]

** DONE list
   CLOSED: [2018-10-08 Mo 21:06]

#+begin_src emacs-lisp
  (quote (cons 2 (cons 3 (cons 4 ()))))
  ;; (cons 2 (cons 3 (cons 4 nil)))
  (quote (2 . (3 . (4 . ()))))
  ;; (2 3 4)
#+end_src

#+begin_src emacs-lisp
  (list (cons 2 (cons 3 (cons 4 ()))))
  ;; ((2 3 4))
  (list (quote(2 . (3 . (4 . ())))))
#+end_src

** DONE print
   CLOSED: [2018-10-08 Mo 20:28]
** DONE read
   CLOSED: [2018-10-08 Mo 20:28]
** DONE type
   CLOSED: [2018-10-08 Mo 21:30]

** TODO info

* Types
 - Symbol
 - Number
 - String
 - pair (cons-cell)
 - lambda function lambda
 - built-in function

* Arbeitsweise

 1) Parse to AST
 2) Start with namespace only containing the built-ins
 3) every AST node has its own namespace,
    inherting the one from its parent (pointer /
    references) because when a function sets a
    variable within an upper namespace it should
    infact change the environment even if the
    function exited

(progn (setq x 4)(* x 2))