Lecture 13 Examples

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PROGRAM	DEMONSTRATES THE USE OF
except1.cpp	Demonstrates exception handling with the try and catch functions and the operator throw.
except1a.cpp	Demonstrates exception handling with a throw statement that has no catch to receive the value.
except1b.cpp	Demonstrates the throw of a variable instead of a value.
except1c.cpp	Demonstrates the throw of a variable instead of a value. It is the same as except1b.cpp except the signature of the catch() is only a data type and not a data type followed by a variable. However, since there is not variable to pass in the value passed can not be used in the body of the catch().
except2.cpp	Demonstrates the throw of a programmer defined data type rather than a system data type as in except1c.cpp.
except3.cpp	Demonstrates the throw of a value for which there is no catch. In this case the program is aborted
except4.cpp	Demonstrates the throw of a variable. It has several calls to the function but not all execute the throw.
except5.cpp	Demonstrates the throw of a variable which could be any data type or a string.
except6.cpp	Demonstrates the use of a default catch() which catches all throws.
except7.cpp	Demonstrates the default catch() but as only one of several alternatives. This is a better approach than except6.cpp where the default caught everything.
except8.cpp	Demonstrates the restriction on a function as to the type of throws which can occur.
except9.cpp	Demonstrates that a catch() may contain a throw as well as a try block and that a throw does not need to have an argument.
fractions.cpp	Demonstrates how a class can be made robust by using exceptions.
ratio.cpp	Contains an example of throwing a base and a derived object to determine which catch() should come first.
ratio2.cpp	Contains an example of throwing a base and a derived object to determine which catch() should come first. The catches in this example are reversed those in ratio.cpp

 // program_id         except1.cpp // author                 don voils // date written        11/25/2006 // // description   This program demonstrates //                    exception handling with //                    the try and catch functions //                    and the operator throw. // #include <iostream> using namespace std; void main() {  cout << "This is the start." << endl;  try  {   cout << "Got into the try block." << endl;   throw 34;   cout << "This line of code is not reached." << endl;  }  catch(int i)  {   cout << "The program throw number " << i << endl;  }  cout << "The program will now end" << endl;  char resp;  cout << endl << endl << "Continue? ";  cin >> resp;  cout << endl << endl; } // program_id         except1a.cpp // author                don voils // date written       11/25/2006 // // description   This program demonstrates //                    exception handling with //                    a throw statement that has no catch //                    to receive the value. The program will abort. // #include <iostream> using namespace std; void main() {  cout << "This is the start." << endl;  try  {   cout << "Got into the try block." << endl;   throw 34;   cout << "This line of code is not reached." << endl;  }  catch(char i)  {   cout << "The program throw number " << i << endl;  }  cout << "The program will now end" << endl;  char resp;  cout << endl << endl << "Continue? ";  cin >> resp;  cout << endl << endl; } // program_id         except1b.cpp // author                don voils // date written       11/25/2006 // // description   This program demonstrates the //                     throw of a variable instead //                     of a value. Compare this program //                     with except1c.cpp // #include <iostream> using namespace std; // the variable theValue is passed to catch() by value // since the variable theValue has moved out of scope. void main() { cout << "This is the start." << endl; try {   int theValue = 34;   cout << "Got into the try block." << endl;   throw theValue;   cout << "This line of code is not reached." << endl; } catch(int i) {   cout << "The program throw number " << i << endl; } cout << "The program will now end" << endl; char resp; cout << endl << endl << "Continue? "; cin >> resp; cout << endl << endl; } // program_id           except1c.cpp // author                  don voils // date written         11/25/2006 // // description    This program demonstrates the //                      throw of a variable instead //                      of a value. It is the same as //                      except1b.cpp except the signature //                      of the catch() is only a data //                      type and not a data type followed //                      by a variable. However, since //                      there is not a variable to pass in //                      the value passed can not be used //                      in the body of the catch(). // #include <iostream> using namespace std; void main() { cout << "This is the start." << endl; try {   int value = 34;   cout << "Got into the try block." << endl;   throw value;   cout << "This line of code is not reached." << endl; } catch(int) {   cout << "The program throw an integer" << endl; } cout << "The program will now end" << endl; char resp; cout << endl << endl << "Continue? "; cin >> resp; cout << endl << endl; } // program_id         except2.cpp // author                 don voils // date written        11/25/2006 // // description  This program demonstrates the //                    throw of a programmer defined //                   data type rather than a system //                   data type as in except1c.cpp. // #include<iostream> using namespace std; class DivideByZeroError {  private:   const char *message;  public:   // The colin in the definition of DivieByZeroError()   // is required since message is a constant.   //   DivideByZeroError() : message("Divide by zero"){ }   // Notice that printMessage() is a const function   // and therefore it may manipulate the const data   // member message.   //   void printMessage() const {cout << message;} }; float quotient(int num1, int num2) {    //  Should the following boolean be true, the    //  throw is called. In this case an object of the    //  DivideByZeroError class is defined. While the    //  name of this object is not specified, the    //  contents of the object, namely the error message    //  is passed to the object in the argument of the    //  catch(DivideByZero) instance. This object therefore    //  prints in the called catch();    //   if (num2==0)     throw DivideByZeroError();   return (float) num1/ num2; } int main() {  int numb1,     numb2;  cout << "Enter the dividend of the quotient: ";  cin >> numb1;  cout << "Enter the divisor of the quotient: ";  cin >> numb2;  try  {   float result = quotient(numb1, numb2);   cout << "The quotient is: " << result << endl;  }  // If the try block terminates correctly, the following  // catch is not called and program execution begins after  // it.  //  // Notice that the program will return a 1 to the OS if  // the program terminated by a zero division but it  // returns a 0 if the program terminates normally.  //  catch(DivideByZeroError error)  {  cout << "Error ";  error.printMessage();  cout << endl;  return 1;  }  char resp;  cout << endl << endl << "Continue? ";  cin >> resp;  cout << endl << endl;  return 0; } // program_id          except3.cpp // author                  don voils // date written        11/25/2006 // // description   This program demonstrates the //                     throw of a value for which //                     there is no catch. In this case //                     the program is aborted. // #include<iostream> using namespace std; void main() {  cout << "This is the start." << endl;  try  {     cout << "Got into the try block." << endl;    throw 34;    cout << "This line of code is not reached." << endl;  }  catch(char i)  {   cout << "The program throw char is " << i << endl;  }  cout << "The program will now end." << endl;  char resp;  cout << endl << endl << "Continue? ";  cin >> resp;  cout << endl << endl; } // program_id          except4.cpp // author                  don voils // date written         11/25/2006 // // description   This program demonstrates the //                     throw of a variable. It has //                     several calls to the function //                     but not all execute the throw. // // #include<iostream> using namespace std; void MYTEST(int value) {    cout << "Inside of MYTEST. The value is: "         << value << endl;    if(value)        throw value; } void main() {    cout << "Start of main() " << endl;    try    {       cout << "Inside of try block" << endl;       MYTEST(0);       MYTEST(1);       MYTEST(2);    }    catch(int value)    {       cout << "Caught the value " << value << endl;    }    cout << "This is the end of main() " << endl;    char resp;    cout << endl << endl << "Continue? ";    cin >> resp;    cout << endl << endl; } // program_id          except5.cpp // author                 don voils // date written        11/25/2006 // // description   This program demonstrates the //                     throw of a variable which could //                     be any data type or a string. // #include<iostream> using namespace std; void MYTEST(int value) {    try    {       if(value)          throw value;       else          throw "The Value is zero";    }    catch(int value)    {       cout << "Caught the value " << value << endl;    }    catch(char *message)    {       cout << "The message is: " << message << endl;    } } void main() {    cout << "Start of main() " << endl;    MYTEST(1);    MYTEST(2);    MYTEST(0);    MYTEST(3);    cout << "The successful end of main() " << endl;    char resp;    cout << endl << endl << "Continue? ";    cin >> resp;    cout << endl << endl; } // program_id          except6.cpp // author                  don voils // date written         11/25/2006 // // description   This program demonstrates the //                     use of a default catch() which //                     catches all throws. // // // #include<iostream> using namespace std; void MYTEST(int value) {    try    {       if(value==1)          throw value;       if(value==2)          throw "Value is zero";       if(value==0)          throw 452.22;    }    catch(…)    {       cout << "Caught some value "<< endl;    } } void main() {    cout << "Start of main() " << endl;    MYTEST(1);    MYTEST(2);    MYTEST(0);    cout << "The end of main() " << endl;    char resp;    cout << endl << endl << "Continue? ";    cin >> resp;    cout << endl << endl; } // program_id          except7.cpp // author                  don voils // date written        11/25/2006 // // description   This program demonstrates the //                     default catch() but as only //                     one of several alternatives. //                     This is a better approach than //                     except6.cpp where the default //                     caught everything. // #include<iostream> using namespace std; void MYTEST(int value) {    try    {       if(value==1)           throw value;       if(value==2)           throw "Value is zero";       if(value==0)          throw 452.22f;    }    catch(float value)    {       cout << "Caught a float of value " << value << endl;    }    catch(int value)    {       cout << "Caught an int of value " << value << endl;    }    catch(…)    {       cout << "Caught some value "<< endl;    } } void main() {    cout << "Start of main() " << endl;    MYTEST(1);    MYTEST(2);    MYTEST(0);    cout << "The end of main() " << endl;    char resp;    cout << endl << endl << "Continue? ";    cin >> resp;    cout << endl << endl; } // program_id          except8.cpp // author              don voils // date written       11/25/2006 // // description   This program demonstrates the //               restriction on a function as to //               the type of throws that can //               occur. What is supposed to happen here, //               is that only int and char values may be //               thrown. However, you will notice that //               this program also processes a double //               in Microsoft Visual Studio. In addition //               an warning occurs stating that this //               is a disallowed feature of Visual Studio. // // #include<iostream> using namespace std; void MYTEST(int value) throw(int, char) {    try    {       if(value==1)          throw value;       if(value==2)          throw 'V';       if(value==0)          throw 452.22;    }    catch(char value)    {       cout << "Caught a char of value: " << value << endl;    }    catch(int value)    {       cout << "Caught an int of value: " << value << endl;    }    catch(…)    {       cout << "Caught a value not on the throw list " << endl;    } } void main() {    cout << "Start of main() " << endl;    MYTEST(1);    MYTEST(2);    MYTEST(0);    cout << "The end of main() " << endl;    char resp;    cout << endl << endl << "Continue? ";    cin >> resp;    cout << endl << endl; } // program_id          except9.cpp // author              don voils // date written       11/25/2006 // // description   This program demonstrates that //               a catch() may contain a throw //               as well as a try block and //               that a throw does not need //               to have an argument. What //               happened to the first throw //               value? // // #include<iostream> using namespace std; void MYTEST() {  try  {   throw "USA";  }  catch(char* value)  {   cout << "Caught " << value      << " inside MYTEST." << endl;   throw;  } } void main() {  cout << "Start of main() " << endl;  try  {    MYTEST();  }  catch(char* value)  {     cout << "Inside of main() " << endl;     cout << "Caught " << value << " inside of main() from a throw by MYTEST()"<< endl;  }  catch(…)  {     cout << "Not a string" << endl;  }  cout << "The end of main() " << endl;  char resp;  cout << endl << endl << "Continue? ";  cin >> resp;  cout << endl << endl; } // program_id   fractions.cpp // written_by   don voils // date_written 12/1/2006 // // description  This program demonstrates //              how a class can be made robust //              by using exceptions. // #include<iostream> using namespace std; class Fractions {   private:     long top;     long bottom;   public:     Fractions()     {          top = 0;          bottom = 1;     }     Fractions(long t, long b)     {       if(b==0)       {                 throw true;       }       top = t;       bottom = b;       reduce();     }     void setTop(long t)     {       top = t;     }     void setBottom(long b)     {       if(b==0)       {                throw true;       }       bottom = b;     }     long getTop()     {              return top;     }     long getBottom()     {              return bottom;     }     Fractions operator+(Fractions theRight)     {              Fractions temp;              temp.top = top*theRight.bottom + bottom*theRight.top;              temp.bottom = bottom * theRight.bottom;              temp.reduce();              return temp;     }     Fractions operator-(Fractions theRight)     {              Fractions temp;              temp.top = top*theRight.bottom - bottom*theRight.top;              temp.bottom = bottom * theRight.bottom;              temp.reduce();              return temp;     }     Fractions operator*(Fractions theRight)     {              Fractions temp;              temp.top = top*theRight.top;              temp.bottom = bottom*theRight.bottom;              temp.reduce();              return temp;     }     Fractions operator /(Fractions theRight)     {              Fractions temp;              if(theRight.top==0)                throw true;              temp.top = top * theRight.bottom;              temp.bottom = bottom * theRight.top;              temp.reduce();              return temp;     }            long newGcd(long numb1, long numb2)            {              return (numb1<0) ? newGcd(-numb1,numb2):((numb2==0)?                                   numb1:newGcd(numb2,numb1%numb2));            }     void reduce()     {       long gcd = newGcd(top,bottom);       top = top/gcd;       bottom = bottom/gcd;     }     void show()     {       cout << " " << top << '/' << bottom << " ";     }           friend ostream &operator << (ostream &stream, Fractions ab);           friend istream &operator >> (istream &stream, Fractions &ab); }; ostream &operator << (ostream &stream, Fractions ab) {    stream << " " << ab.top << "/";    stream << ab.bottom << " ";    return stream; } istream &operator >> (istream &stream, Fractions &ab) {    char slash;    stream >> ab.top >> slash >> ab.bottom;    if(ab.bottom==0)           throw true;    ab.reduce();    return stream; } void main() {      bool again = false;      Fractions theFirst, theSecond;      do      {           again = false;           cout << endl << "Enter the first fraction? ";           try           {                cin >> theFirst;           }           catch(bool value)           {                if(value)                {                      cout << endl << "You must enter a non-zero number for"                         << " the bottom of the fraction." << endl;                      again = true;                }           }      }while(again);      do      {          again = false;          cout << endl << "Enter the second fraction? ";          try          {               cin >> theSecond;          }          catch(bool value)          {               if(value)               {                    cout << endl << "You must enter a non-zero number for"                                                   << " the bottom of the fraction." << endl;                    again = true;               }          }      }while(again);      Fractions theSum = theFirst + theSecond;      cout << endl;      cout << theFirst;      cout << " + ";      cout << theSecond;      cout << " = ";      cout << theSum << endl;      Fractions theDifference = theFirst - theSecond;      cout << endl;      cout << theFirst;      cout << " - ";      cout << theSecond;      cout << " = ";      cout << theDifference << endl;      Fractions theProduct = theFirst * theSecond;      cout << endl;      cout << theFirst;      cout << " * ";      cout << theSecond;      cout << " = ";      cout << theProduct << endl;      try      {           if(theSecond.getTop()==0)                 throw true;           Fractions theQuotient = theFirst / theSecond;           cout << endl;           cout << theFirst;           cout << " / ";           cout << theSecond;           cout << " = ";           cout << theQuotient;      }      catch(bool value)      {           if(value)              cout << endl << "The top of the second fraction must be "                   << " non-zero. " << endl;      }      cout << endl << endl; } // program_id        ratio2.cpp // author            don voils // date written     11/25/2006 // // description   This program is similar to //               ratio.cpp except the catch( ) //               functions have been switched. //               In this one the first catch( ) //               is for the derived class and //               the second is for the base //               class. Does it make a difference? // // // #include<iostream> using namespace std; class Ratio {  private:   int top,     bottom;  public:   void setRatio(int t, int b)   {    top = t; bottom=b;   }   int showTop()   {    return top;   }   int showBottom()   {    return bottom;   } }; class NewRatio : public Ratio {  public:   NewRatio operator *(NewRatio ratio1)   {    NewRatio temp;    int a = (showTop())*(ratio1.showTop());    int b = (showBottom())*(ratio1.showBottom());    temp.setRatio(a,b);    return temp;   } }; void classHandler(int value) {  Ratio a;  a.setRatio(3,4);  NewRatio b;  b.setRatio(5,6);  try   {    if(value==0)     throw a;    if(value==1)     throw b;   }   catch(NewRatio b)   {    cout << "The NewRatio object is "         << b.showTop() << '/' << b.showBottom() << endl;   }   catch(Ratio a)   {    cout << "The Ratio object is "         << a.showTop() << '/' << a.showBottom() << endl;   } } void main() {  cout << "At the start of main()" << endl;  classHandler(0);  classHandler(1);  cout << "At the end of main()" << endl; } // program_id        ratio.cpp // author            don voils // date written     11/25/2006 // // description   This program is similar to //               ratio2.cpp except the catch( ) //               functions have been switched. //               In this one the first catch( ) //               is for the base class and //               the second is for the derived //               class. Does it make a difference? // // // #include<iostream> using namespace std; class Ratio {  private:   int top,      bottom;  public:   void setRatio(int t, int b)   {    top = t; bottom=b;   }   int showTop()   {    return top;   }   int showBottom()   {    return bottom;   } }; class NewRatio : public Ratio {  public:   NewRatio operator *(NewRatio ratio1)   {    NewRatio temp;    int a = (showTop())*(ratio1.showTop());    int b = (showBottom())*(ratio1.showBottom());    temp.setRatio(a,b);    return temp;   } }; void classHandler(int value) {  Ratio a;  a.setRatio(3,4);  NewRatio b;  b.setRatio(5,6);  try  {   if(value==0)     throw a;   if(value==1)     throw b;  }  catch(Ratio a)  {   cout << "The ratio object is "        << a.showTop() << '/' << a.showBottom() << endl;  }  catch(NewRatio b)  {   cout << "The new_ratio object is "        << b.showTop() << '/' << b.showBottom() << endl;  } } void main() {  cout << "At the start of main()" << endl;  classHandler(0);  classHandler(1);  cout << "At the end of main()" << endl; }