 Such a definition might at first appear circular in virtue of the fact that the value of \(\fact(x)\) on the left hand side is defined in terms the same function on the righthand side. However a characteristic feature of recursive definitions is that they allow for the values of functions which they describe to be calculated by successively “unwinding” the clause for \(x &gt; 0\) until the clause for \(x = 0\) (the so-called base case) is reached. For instance the value of \(fact(4)\) may be calculated using the preceding definition as follows: