1. n :
2. 0 < n 3. m:, f, x:Top.
3. (primrec((n - 1)+m;x.x;i,g. f o g)(x))
3. ~
3. (primrec(n - 1;x.x;i,g. f o g)(primrec(m;x.x;i,g. f o g)(x)))
4. m :
5. f : Top
6. x : Top
7. (n = 0)
8. (n+m = 0)
(primrec((n+m) - 1;x.x;i,g. f o g)(x))
~
(primrec(n - 1;x.x;i,g. f o g)(primrec(m;x.x;i,g. f o g)(x)))