(defmacro mfor (:form f (var . range-triplets) . forms)
  (with-gensyms (body toval stepval test)
    ^(let (,var)
       (flet ((,body () ,*forms))
         ,*(append-each ((rt (tuples 3 range-triplets)))
             (mac-param-bind f (from to step) rt
               ^((set ,var ,from)
                 (for* ((,toval ,to)
                        (,stepval ,step)
                        (,test (if (<= ,var ,toval)
                                 (fun <=) (fun >=))))
                       ([,test ,var ,toval])
                       ((inc ,var ,stepval))
                   (,body)))))))))

(let ((prod 1) (sum 0)
      (x 5) (y -5) (z -2)
      (one 1) (three 3) (seven 7))
  (mfor (j (- three)    (expt 3 3)         three
           (- seven)    seven              x
           555          (- 550 y)          1
           22           -28                (- three)
           1927         1939               1
           x            y                  z
           (expt 11 x)  (succ (expt 11 x)) 1)
    (upd sum (+ (abs j)))
    (if (and (< (abs prod) (ash 1 27))
             (nzerop j))
      (upd prod (* j))))
  (put-line `sum = @sum; prod = @prod`))