While loop with OR conditions, beginner

I am just beginning and going through Jumping Into C++. I am working #2 in chapter 5 which states... "Write a menu program that lets the user select from a list of options, and if the input is not one of the options, reprint the list"

Code:

#include <iostream>
#include <string>
using namespace std;
int main()
{
    string input = "unknown";
    while ( input != "1" || input != "2" || input != "3" || input != "4" || input != "5")
    {
        cout << "file (1)\t edit (2)\t view (3)\t search (4)\t project (5)\n";
        cout << "Select a function: ";
        cin >> input;
    }
}

No matter what I enter the loop never breaks. I am pretty sure my "while" line is not right but I don't know. I know this is elementary stuff but I want to understand the easy stuff before it gets really hairy.

Suppose input == "1". Then input != "1" is false, so we check if input != "2". Well, it is true that input != "2", so we continue looping. Problem is, when input == "1", you want to stop looping. So, under what conditions does (input != "1" || input != "2" || input != "3" || input != "4" || input != "5") ever evaluate to false? Well, when (input == "1" && input == "2" && input == "3" && input == "4" && input == "5"). Unfortunately, input can only hold one of these values at any one time.

Let me put my logic hat on and ponder a bit.

Thanks for the reply. I will re-tool a little.

You could simplify it a little:

Code:

while( input[0]>'0' && input[0] <'6')

Originally Posted by manasij7479

You could simplify it a little:

Code:

while( input[0]>'0' && input[0] <'6')

That would be wrong though. It should be:

Code:

while (input.length() != 1 || input[0] < '1' || input[0] > '5')

If you want a bit more structure, you can do something like:

Code:

#include <iostream> 
#include <string> 

using namespace std; 

int main() 
{ 
   int choice = 0;
   do
   {
      cout << "file (1)\t edit (2)\t view (3)\t search (4)\t project (5)\t quit (6)\n"; 
      cout << "Select a function: "; 
      cin >> choice; 
      switch( choice )
      {
         case 1: cout << "file" << endl;
         case 2: cout << "edit" << endl;
         case 3: cout << "view" << endl;
         case 4: cout << "search" << endl;
         case 5: cout << "project" << endl;
      }
   } 
   while( choice != 6 ) //loop stops on 6
}