(define (null? args)
(eq? args ()))
+(define (caar l) (car (car l)))
+(define (cadr l) (car (cdr l)))
+(define (cdar l) (cdr (car l)))
+(define (cddr l) (cdr (cdr l)))
+(define (cadar l) (car (cdr (car l))))
+
; Join two lists together
(define (join l1 l2)
(if (null? l1)
()
(append (reverse (cdr l)) (list (car l)))))
-;; LIBRARY FORMS
-(define-macro (let value . body )
- (list (list 'lambda (list (car value)) body)) (cdr value))
+
+;; LIBRARY SPECIAL FORMS
+
+; let
+
+(define (let-vars args)
+ (if (null? args)
+ '()
+ (cons (caar args) (let-vars (cdr args)))))
+
+(define (let-inits args)
+ (if (null? args)
+ '()
+ (cons (cadar args) (let-inits (cdr args)))))
+
+(define-macro (let args . body)
+ `((lambda ,(let-vars args)
+ ,@body) ,@(let-inits args)))
+
+; while
+
+(define-macro (while condition . body)
+ (let ((loop (gensym)))
+ `(begin
+ (define (,loop)
+ (if ,condition
+ (begin ,@body (,loop))))
+ (,loop))))
+
+; cond
+
;; TESTING
+(define-macro (backwards . body)
+ (cons 'begin (reverse body)))
+
+; Test for the while macro.
+(define (count)
+ (define counter 10)
+ (while (> counter 0)
+ (display counter) (newline)
+ (set! counter (- counter 1))))
+
; Basic iterative summation. Run this on large numbers to
; test garbage collection and tail-call optimization.
(define (sum n)