Reading the next line of an input file...

[bkirchner]

This is a homework problem, but I've exhausted all my other resources and I'm turning to you for help!!

I've been given an input file with a series of simple expressions that looks like this:

123.5 + 59.3
198.7 / -26
125 $ 28
89.3 * 2.5
178.9 - 326.8
198.7 / 0
34.0 ? 10
236 % 45

The program terminates once it hits the expression with the "?" operator. I've written the whole program, but I can't figure out how to read the input file. Heres what I have so far.... but the problem is that it reads the first line over and over and over again.

  //readExpression()
       fin >> operand1 >> function >> operand2;
       while (function != '?')
       {
               //echoExpression()
               fout << operand1 << function << operand2;
               //evaulateExpression()
               switch (function)
                       {
                       case '+': solution=operand1+operand2;
                       break;
                       case '-': solution=operand1-operand2;
                       break;
                       case '*': solution=operand1*operand2;
                       break;
                       case '/': if (operand2==0)
                               {
                               fout <<operand1<<function<<operand2
                                        <<"  Division by zero produces an undefined result.";
                               return 2;
                               }
                       else solution=operand1/operand2;
                       break;
                       default:
                               fout << operand1 << function << operand2
                                        <<"  Encountered an unknown operator.";
                       return 3;
                       break;
                       }
               fin >> operand1 >> function >> operand2;

       }

So I ask: how do I get it to go to the next, and next, and next line?