// Fig. 6.29: fig06_29.cpp
// Demonstrating the recursive function factorial.
#include <iostream>
#include <iomanip>
using namespace std;

unsigned long factorial( unsigned long ); // function prototype

int main()
{
   // calculate the factorials of 0 through 10
   for ( int counter = 0; counter <= 10; ++counter )
      cout << setw( 2 ) << counter << "! = " << factorial( counter ) 
         << endl;
} // end main

// recursive definition of function factorial
unsigned long factorial( unsigned long number )
{
   if ( number <= 1 ) // test for base case
      return 1; // base cases: 0! = 1 and 1! = 1
   else // recursion step
      return number * factorial( number - 1 );
} // end function factorial


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