/*
    testfunc11.cpp
    CIS 150
    2008-06-10
    David Klick
   
    Factorial functions.
*/

#include <iostream>
#include <iomanip>
using std::cin;
using std::cout;
using std::setw;

int factn(int);  // non-recursive factorial function
int factr(int);  // recursive factorial function
void cont();

int main(int argc, char* argv[]) {
    int i;

    cout << "Non-recursive factorial calcs:\n";
    for (i=0; i<=10; i++) {
        cout << "The factorial of " << setw(2) << i
             << " is " << setw(7) << factn(i) << '\n';
    }
   
    cout << "\nRecursive factorial calcs:\n";
    for (i=0; i<=10; i++) {
        cout << "The factorial of " << setw(2) << i
             << " is " << setw(7) << factr(i) << '\n';
    }

    cont();
    return 0;
}

/*
    int fact(int n);
   
    Arguments:
        int n: an arbitrary integer (s/b >= 0)
   
    Returns: The factorial of the argument n if
        n is >= 0, otherwise 1.
      
    Non-recursive factorial function
*/
int factn(int n) {
    int prod = 1;
    while (n > 0) prod *= n--;
    return prod;
}

/*
    int factr(int n);
   
    Arguments:
        int n: an arbitrary integer (s/b >= 0)
   
    Returns: The factorial of the argument n if
        n is >= 0, otherwise 1.
      
    Recursive factorial function
*/
int factr(int n) {
    if (n < 2) return 1;
    return n * factr(n-1);
}

/*
    void cont();
   
    Arguments: none
    
    Returns: nothing
   
    Clears input buffer and pauses waiting for user 
    to press Enter.
*/
void cont() {
    if (cin.rdbuf()->sungetc() != -1 && cin.get() != '\n') cin.ignore(80,'\n');
    cout << "Press enter to continue...";
    cin.get();
}

/*
    Sample output:
   
    Non-recursive factorial calcs:
    The factorial of  0 is       1
    The factorial of  1 is       1
    The factorial of  2 is       2
    The factorial of  3 is       6
    The factorial of  4 is      24
    The factorial of  5 is     120
    The factorial of  6 is     720
    The factorial of  7 is    5040
    The factorial of  8 is   40320
    The factorial of  9 is  362880
    The factorial of 10 is 3628800

    Recursive factorial calcs:
    The factorial of  0 is       1
    The factorial of  1 is       1
    The factorial of  2 is       2
    The factorial of  3 is       6
    The factorial of  4 is      24
    The factorial of  5 is     120
    The factorial of  6 is     720
    The factorial of  7 is    5040
    The factorial of  8 is   40320
    The factorial of  9 is  362880
    The factorial of 10 is 3628800
*/