Day28:错误处理

讲一个经典案例除以0，首先创造一个DivideByZeroEXception类别继承runtime_error。在C++中double除以0并不会报错，所以主动用throw丢出DivideByZeroEXception，并在catch段落呼叫what()方法显示错误原因，最外面用while()产生一个无限回圈

while ( cin >> number1 >> number2 ) 
{
   // try block contains code that might throw exception
   // and code that should not execute if an exception occurs
   try 
   {
      result = quotient( number1, number2 );
      cout << "The quotient is: " << result << endl;
   } // end try

   // exception handler handles a divide-by-zero exception
   catch ( DivideByZeroException &divideByZeroException ) 
   {
      cout << "Exception occurred: " 
         << divideByZeroException.what() << endl;
   } // end catch

   cout << "\nEnter two integers (end-of-file to end): ";
} // end while

详细范例见Fig. 16.1: DivideByZeroException.h与Fig. 16.2: Fig16_02.cpp