Let's make some simple programs!

Because I know that half of /prog/ can't program, let's make simple ones!

---------------------- MySavings.java ----------------------

/**
 * @(#)MySavings.java
 *
 * MySavings application
 *
 * @author Tim H
 * @version 1.00 2010/5/7
 */
 
import java.util.Scanner;

public class MySavings {
   
    public static void printInterface() {
        System.out.print(
            "1. Show total in bank.\n" +
            "2. Add a penny.\n" +
            "3. Add a nickel.\n" +
            "4. Add a dime.\n" +
            "5. Add a quarter.\n" +
            "6. Take money of out bank.\n" +
            "Enter 0 to quit.\n" +
            "Enter your choice: "
            );
    }
   
    public static void main(String[] args) {
       
        Scanner input = new Scanner(System.in);
        int choice = 1;
        int moneyChoice = 0;
        double amount = 0;
       
        PiggyBank bank = new PiggyBank();
       
        while(choice > 0){
            printInterface();
            choice = input.nextInt();
           
            switch(choice){
                case 0: System.out.println("(c)Tim H 2010\nHave a nice day!"); break;
                case 1: System.out.println("Your current total is: " + bank.GetTotal()); break;
                case 2:
                case 3:
                case 4:
                case 5: moneyChoice = choice - 2; bank.AddMoney(moneyChoice); break;
                case 6:
                    System.out.print("Enter the amount you wish to withdraw: ");
                    amount = input.nextDouble();
                    bank.SubtractTotal(amount);
                    break;
                default:
                    System.out.println("Please enter a choice between 1-6!");
                    break;
            }
               
        }
---------------------- PiggyBank.java ----------------------


class PiggyBank {
    double total;
   
   
    public PiggyBank(){
        total = 100;
    }
   
    public void AddMoney(int choice){
        switch (choice) {
            case 0:
                total += 0.01;
                System.out.println("One penny added to total!\nYour total is now: " + total);
                break;
            case 1:
                total += 0.05;
                System.out.println("One nickel added to total!\nYour total is now: " + total);
                break;
            case 2:
                total += 0.10;
                System.out.println("One dime added to total!\nYour total is now: " + total);
                break;
            case 3:
                total += 0.25;
                System.out.println("One quarter added to total!\nYour total is now: " + total);
                break;
           
        }
    }
   
    public double GetTotal(){
        return total;
    }
   
    public void SubtractTotal(double amount){
        total -= amount;
        System.out.println(amount + " has been subtracted from your total!\nYour total is now: " + total);
    }
}

    }
   
}

>>27
fact = lambda n: int(round(math.e**reduce(lambda a, b: a + math.log(b), range(1, n+1), 0)))

Mine's shorter.

>>33
Too bad that by the time you get to fact(100) the error of that approximation is up to about 6.9 x 10¹⁴⁴.

(Exactly 6900274882930203761252337810247937431593403625973980018479912680937406453445938682543730846893682459286692158877000328163287360910292339254099968, actually)

>>35
But the nice part of it is that the error increases in a beautiful exponential curve, so you can get a good estimate of how big it's going to be and adjust the result based on that.
The only problem is knowing the sign of the error, though that problem apparently goes away when the number you're taking the factorial of is big enough. Here's a graph of the value of the approximate function minus the value of the actual factorial:

http://i.imgur.com/bjeoj.png

(Where the graph is broken the error is negative, except for x ≤ 17, where it's 0. The absolute values of the error form a pretty straight line.)