module Integer 
import foreign c value
        subInt  : [r1 r2 r3 : Region]
                . Int r1 -(Pure | Use r3)> 
                  Int r2 -(Read r1 + Read r2 + Alloc r3 | Use r1 + Use r3)> 
                  Int r3

        mulInt  : [r1 r2 r3 : Region]
                . Int r1 -(Pure | Use r3)> 
                  Int r2 -(Read r1 + Read r2 + Alloc r3 | Use r1 + Use r3)> 
                  Int r3
with letrec

fac    [r : Region] 
       (acc : Int r) {Pure | Use r}
       (n   : Int r) {Read r + Alloc r | Use r} : Int r
 =  case n of { 
        I# i -> 
         case i of {
                0i#   -> acc;
                1i#   -> acc;
                _       -> fac [r] (mulInt [:r r r:] acc n)
                                   (subInt [:r r r:] n (I# [r] 1i#));
         };
 }