I/O
-------------------

   - please read Section 2.2, 2.6.4 of the book.

   - output

     - allows multiple values to be printed in one statement
     
     using namespace std;
     cout << a << b << endl;

     - formatted output
       #include <iomanip>
       - To set width of the next output
       cout << setw(8);  // spaces (right justified) output 8 characters
       cout << setprecision(2); // precision for floating point numbers
       cout << 3.423 << endl;   // prints "....3.42"
       - setprecision has to be set once
       - setw has to be set everytime some output is printed
    
   - input
   
     int a;
     cin >> a;
                                                    
     - suppose you type in 2.3, followed by newline
     
        ___________________
       | 2  | .  | 3  | \n |
       |____|____|____|____|
       
       - a gets 2;
       - cin stops at .
       - if you were to read an integer again, nothing would be read
     
     - what if you typed a string instead of a number
     
        ___________________
       | t  | e  | n  | \n |
       |____|____|____|____|
      
       - a would not get any value
       - cin would be in a "failed" state after the first read
	 - worse, the following could cause an infinite loop
         while (a < 10) {
    	     cin >> a;
    	     cout << a << endl;
         }
     
     - what if you typed 2, followed by space, 3 and newline

        ___________________
       | 2  |    | 3  | \n |
       |____|____|____|____|
       
       - a would get 2 only after the newline
       - a subsequent read would get the 3 value
     
     - solution to cin failure
       - test for failure after each input
         cin >> x;
         if (!cin.fail()) {
  		// correct input
  	 } else {
	 	// bad input
	 }
	 
       - another way

         while (cin >> x) {
	 	// correct input
	 }