letrec: Transformation nach rec

(DCPL Fig. 6.7 p. 233)

(letrec ((n1 x1) .. (nk xk)) y) 
->
(app (rec t 
          (lam s 
               (s (t (abs (n1..nk) x1)
                     ...
                     (abs (n1..nk) xk) ))))
     (abs (n1..nk) y) )