gistfile1.scm

(define-macro (do init test . expr)
  (let ((bindings (map (lambda (x) (cons (car x) (list (cadr x)))) init))
       (steps (map (lambda (x) (if (< 2 (length x)) (caddr x) (car x))) init))
       (condition (car test))
       (endresult (cdr test))
       (loop-name (gensym)))

    `(let ,loop-name ,bindings
       (if (not ,condition)
           (begin ,(car expr) ,(cons loop-name steps))
           ,@endresult))))