The natural numbers can be defined recursively as follows:

• 0 is a natural number.
• if $n$ is a natural number, then so is the successor of $n$

We can easily represent this in OCaml using corresponding constructors:

type nat = Zero | Succ of nat

Implement the following functions for natural numbers:

First convert between integers and naturals in the file conv.ml

1. int_to_nat
   int_to_nat : int -> nat converts an integer to natural.
2. nat_to_int
   nat_to_int : nat -> int converts a natural to integer.

Then implement some operations on naturals in the file ops.ml:

1. add
   add : nat -> nat -> nat adds two natural numbers.
2. mul
   mul : nat -> nat -> nat multiplies two natural numbers.
3. pow
   pow : nat -> nat -> nat a call pow a b computes $a^b$.
4. leq
   leq : nat -> nat -> bool a call leq a b computes $a\le b$

You are not allowed to use integers to implement the operations on naturals!