// FactorialThrow - the factorial function which throws
//                  an object containing more infomation
//                  than a single string
#include <stdio.h>
#include <iostream.h>
#include <string.h>

// Exception - generic exception handling class
class Exception
{
  public:
    // construct an exception object with a description
    // of the problem along with the file and line #
    // where the problem occurred
    Exception(char* pMsg, char* pFile, int nLine)
    {
        this->pMsg = new char[strlen(pMsg) + 1];
        strcpy(this->pMsg, pMsg);

        strncpy(file, pFile, sizeof file);
        file[sizeof file - 1] = '\0';
        lineNum = nLine;
    }

    // display - output the contents of the
    //           current object to the output stream
    virtual void display(ostream& out)
    {
        out << "Error <"
            << pMsg 
            << ">\n";
        out << "Occured on line #"
            << lineNum
            << ", file " 
            << file 
            << endl;
    }

  protected:
    // error message
    char* pMsg;

    // file name and line number where error occurred
    char file[80];
    int lineNum;
};

// factorial - calculate the factorial of nBase which
//             is equal to nBase * (nBase - 1) *
//             (nBase - 2) * ...
int factorial(int nBase)
{
    // if nBase < 0...
    if (nBase <= 0)
    {
        // ...throw an error
        throw     Exception("Negative argument to factorial",
                            __FILE__,
                            __LINE__);
    }                       

    // begin with an "accumulator" of 1
    int nFactorial = 1;

    // loop from nBase down to one, each time
    // multiplying the previous accumulator value
    // by the result
    do
    {
        nFactorial *= nBase;
    } while (--nBase > 1);

    // return the result
    return nFactorial;
}

int main(int nArgc, char* pszArgs[])
{
    // call factorial in a loop. Catch any exceptions
    // that the function might generate
    try
    {
        for (int i = 6; ; i--)
        {
            cout << "factorial(" << i << ") = " << factorial(i) << "\n";
        }
    }
     // catch an Exception object
     catch(Exception x)
     {
          // use the built-in display member function
          // to display the object contents to the
          // error stream
          x.display(cerr);
     }
    return 0;
}