Exponentiation is Primitive Recursive

Theorem
The function $\exp: \N^2 \to \N$, defined as:
 * $\exp \left({n, m}\right) = n^m$

is primitive recursive‎.

Proof
We observe that:
 * $\exp \left({n, 0}\right) = n^0 = 1$

and that
 * $\exp \left({n, m + 1}\right) = n^\left({m + 1}\right) = \left({n^m}\right) \times n = \operatorname{mult} \left({\exp \left({n, m}\right), n}\right)$.

Thus $\exp$ is defined by primitive recursion from the primitive recursive function ‎$\operatorname{mult}$.

Hence the result.