test.html

<html>
<head>
  <title>LISP Interpreter</title>
  <script src="jquery-1.7.2.min.js"></script>
  <script src="jquery.terminal-0.4.15.js"></script>
  <script src="lisp.js"></script>
  <script src="lisp-parser.js"></script>
  <script src="lisp-eval.js"></script>
  <script src="lisp-macro.js"></script>
  <script src="lisp-builtins.js"></script>
  <script src="lisp-repl.js"></script>
  <script src="lisp-test.js"></script>
  <link rel="stylesheet" type="text/css" href="terminal.css" />
  <script>
    $(function() {
          lisp.replTerminal($('#term'));
          lisp.replLoader($('#source'), $('#load'));
          lisp.test();
          $('body').click(function() { lisp.terminal.disable(); });
          $('#clear').click(function () { lisp.terminal.clear(); });
    });
  </script>
</head>
<body>
  <div id="term" style="width: 48%; height: 300px; float: left;"></div>
  <div style="width: 48%; float: right;">
    <textarea id="source" style="width: 100%; height: 300px;">
;; A few examples. Click 'Load source' to load them.

; Closures
(let (count 0)
  (define (counter) (set! count (+ 1 count))))

; You can also define variables
(define x 2)
(set! x 3)

; Let
(let (x 2 y 3) (+ x y))

; Lambda
(set! x (lambda () 'bla))
(x)

; Factorial example
(define (fact n)
  (if (= n 0)
      1
      (* n (fact (- n 1)))))
(fact 5)

; Length example
(define (length list)
  (if (empty? list)
      0
      (+ 1 (length (cdr list)))))
(length '(1 2 3))

; Map example
(define (map func list)
  (if (empty? list)
      nil
      (cons (func (car list))
            (map func (cdr list)))))
(map (lambda (x) (+ x 1)) '(1 2 3))

; And macro example
(defmacro (and x . xs)
  (if (empty? xs)
      x
      `(when ,x (and . ,xs))))
(expand-code '(and a b c d))
; and to demonstrate the short-circuit mechanism:
; ((unknown) should crash when run)
(and (= 2 2) (= 2 3) (unknown))

;; Hygiene in macros
; Consider a simple macro:

(defmacro (bad-swap a b)
  `(let (tmp ,a)
     (set! ,a ,b)
     (set! ,b tmp)))

; Usage example:
(let (x 1 y 2)
   (bad-swap x y)
   (list x y))
; (2 1)

; Unfortunately, this fails if we have a variable called tmp!
(let (x 1 tmp 2)
   (bad-swap x tmp)
   (list x tmp))
; (1 2)

; We solve that by using the gensym function to generate a new name
; that will not conflict with anything else:
(defmacro (swap a b)
  (let (tmp (gensym 'tmp))
    `(let (,tmp ,a)
       (set! ,a ,b)
       (set! ,b ,tmp))))

; Now try:
(expand-code '(swap x tmp))
; (let (#tmp-0 x) (set! x tmp) (set! tmp #tmp-0))

</textarea>
    <input type="button" id="clear" value="Clear terminal" />
    <input type="button" id="load" value="Load source" />
  </div>
</body>
</html>