+
+
+; 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)
+ (define loop (gensym))
+ `(begin
+ (define (,loop)
+ (if ,condition
+ (begin ,@body (,loop))))
+ (,loop)))