mal/elisp/step7_quote.el

;; -*- lexical-binding: t; -*-

(require 'mal/types)
(require 'mal/func)
(require 'mal/env)
(require 'mal/reader)
(require 'mal/printer)
(require 'mal/core)

(defvar repl-env (mal-env))

(dolist (binding core-ns)
  (let ((symbol (car binding))
        (fn (cdr binding)))
    (mal-env-set repl-env symbol fn)))

(defun mal-pair-p (mal-object)
  (let ((type (mal-type mal-object))
        (value (mal-value mal-object)))
    (if (and (or (eq type 'list) (eq type 'vector))
             (not (zerop (length value))))
        t
      nil)))

(defun quasiquote (ast)
  (if (not (mal-pair-p ast))
      (mal-list (list (mal-symbol 'quote) ast))
    (let* ((a (mal-listify ast))
           (a0 (car a))
           (a0... (cdr a))
           (a1 (cadr a)))
      (cond
       ((eq (mal-value a0) 'unquote)
        a1)
       ((and (mal-pair-p a0)
             (eq (mal-value (car (mal-value a0)))
                 'splice-unquote))
        (mal-list (list (mal-symbol 'concat)
                        (cadr (mal-value a0))
                        (quasiquote (mal-list a0...)))))
       (t
        (mal-list (list (mal-symbol 'cons)
                        (quasiquote a0)
                        (quasiquote (mal-list a0...)))))))))

(defun READ (input)
  (read-str input))

(defun EVAL (ast env)
  (catch 'return
    (while t
      (if (and (mal-list-p ast) (mal-value ast))
          (let* ((a (mal-value ast))
                 (a0 (car a))
                 (a0* (mal-value a0))
                 (a1 (cadr a))
                 (a2 (nth 2 a))
                 (a3 (nth 3 a)))
            (cond
             ((eq a0* 'def!)
              (let ((identifier (mal-value a1))
                    (value (EVAL a2 env)))
                (throw 'return (mal-env-set env identifier value))))
             ((eq a0* 'let*)
              (let* ((env* (mal-env env))
                     (bindings (mal-value a1))
                     (form a2))
                (when (vectorp bindings)
                  (setq bindings (append bindings nil)))
                (while bindings
                  (let ((key (mal-value (pop bindings)))
                        (value (EVAL (pop bindings) env*)))
                    (mal-env-set env* key value)))
                (setq env env*
                      ast form))) ; TCO
             ((eq a0* 'quote)
              (throw 'return a1))
             ((eq a0* 'quasiquote)
              (setq ast (quasiquote a1))) ; TCO
             ((eq a0* 'do)
              (let* ((a0... (cdr a))
                     (butlast (butlast a0...))
                     (last (car (last a0...))))
                (when butlast
                  (eval-ast (mal-list butlast) env))
                (setq ast last))) ; TCO
             ((eq a0* 'if)
              (let* ((condition (EVAL a1 env))
                     (condition-type (mal-type condition))
                     (then a2)
                     (else a3))
                (if (and (not (eq condition-type 'false))
                         (not (eq condition-type 'nil)))
                    (setq ast then) ; TCO
                  (if else
                      (setq ast else) ; TCO
                    (throw 'return mal-nil)))))
             ((eq a0* 'fn*)
              (let* ((binds (mapcar 'mal-value (mal-value a1)))
                     (body a2)
                     (fn (mal-fn
                          (lambda (&rest args)
                            (let ((env* (mal-env env binds args)))
                              (EVAL body env*))))))
                (throw 'return (mal-func body binds env fn))))
             (t
              ;; not a special form
              (let* ((ast* (mal-value (eval-ast ast env)))
                     (fn (car ast*))
                     (args (cdr ast*)))
                (if (mal-func-p fn)
                    (let ((env* (mal-env (mal-func-env fn)
                                         (mal-func-params fn)
                                         args)))
                      (setq env env*
                            ast (mal-func-ast fn))) ; TCO
                  ;; built-in function
                  (let ((fn* (mal-value fn)))
                    (throw 'return (apply fn* args))))))))
        (throw 'return (eval-ast ast env))))))

(defun eval-ast (ast env)
  (let ((type (mal-type ast))
        (value (mal-value ast)))
    (cond
     ((eq type 'symbol)
      (let ((definition (mal-env-get env value)))
        (or definition (error "Definition not found"))))
     ((eq type 'list)
      (mal-list (mapcar (lambda (item) (EVAL item env)) value)))
     ((eq type 'vector)
      (mal-vector (vconcat (mapcar (lambda (item) (EVAL item env)) value))))
     ((eq type 'map)
      (let ((map (copy-hash-table value)))
        (maphash (lambda (key value)
                   (puthash key (EVAL value env) map))
                 map)
        (mal-map map)))
     (t
      ;; return as is
      ast))))

(mal-env-set repl-env 'eval (mal-fn (let ((env repl-env)) (lambda (form) (EVAL form env)))))
(mal-env-set repl-env '*ARGV* (mal-list (mapcar 'mal-string (cdr argv))))

(defun PRINT (input)
  (pr-str input t))

(defun rep (input)
  (PRINT (EVAL (READ input) repl-env)))

(rep "(def! not (fn* (a) (if a false true)))")
(rep "(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))")

(defun readln (prompt)
  ;; C-d throws an error
  (ignore-errors (read-from-minibuffer prompt)))

(defun println (format-string &rest args)
  (if (not args)
      (princ format-string)
    (princ (apply 'format format-string args)))
  (terpri))

(defmacro with-error-handling (&rest body)
  `(condition-case err
       (progn ,@body)
     (end-of-token-stream
      ;; empty input, carry on
      )
     (unterminated-sequence
      (let* ((type (cadr err))
             (end
              (cond
               ((eq type 'string) ?\")
               ((eq type 'list) ?\))
               ((eq type 'vector) ?\])
               ((eq type 'map) ?}))))
        (princ (format "Expected '%c', got EOF\n" end))))
     (error ; catch-all
      (println (error-message-string err)))))

(defun main ()
  (if argv
      (with-error-handling
       (rep (format "(load-file \"%s\")" (car argv))))
    (let (eof)
      (while (not eof)
        (let ((input (readln "user> ")))
          (if input
              (with-error-handling
               (println (rep input)))
            (setq eof t)
            ;; print final newline
            (terpri)))))))

(main)