/* factorial.c
 * experimenting with various storage of data with a factorial program
 * 
 * King Chapter 7, Ex. 15.
 * 
 *  What is the largest value of n for which the factorial is correct?
 *  Store the value of factorial in: 
 *      1) short
 *      2) long
 *      3) long long
 *      4) float
 *      5) double
 *      6) long double
 * 
 * Value checks done by Wolfram Alpha
 * 
 * By Cory Spitzer
 * March 25th, 2013
 */

#include <stdio.h>

int main(void){
    int input;
    //short sum; 
        // works for input = 7, but overflows for 8
    //long sum; 
        // works for input = 20, but overflows for 21
    //long long sum; 
        // exactly the same as above with my compiler and 64-bit arch.
    //float sum; 
        // answers start to loose accuracy at input = 16, gives an 
        // answer of 'inf' at input = 35
    //double sum; 
        // keeps accuracy until input = 14, gives 'inf' at input = 35
    long double sum;
        // keeps accuracy until input = 26, gives 'inf' at input = 1755
        
    printf("Enter a positive integer: ");
    scanf("%i", &input);

    sum = input;
    input -= 1;
    while (input > 1) {
        sum *= input;
        input -= 1;
    }
    
    printf("It's factorial is %Lf \n", sum);
    // change %<type> as necessary
    
    return 0;
}