Objectives 1Utilize C exceptions by athrowing bcatching 2Cre

Objectives:

1.Utilize C++ exceptions by

a)‘throw’ing

b)‘catch’ing

2.Create a new class for the purpose of exceptions

Question:

When setting the dimensions of a geometric object, the lengths of the sides should be positive values. Write a program that repeatedly asks for the dimensions of a rectangle and displays the area. Before an error is presented, collected both the length and the width values in a new class called Rectangle.

Create a class DimError, that is used by the new Rectangle class. The following methods must be defined for the Rectangle object:

void Rectangle::setWidth(int width);

void Rectangle::setLength(int length);

If either setWidth or setLength is called with a negative value it throws a DimError that includes a message indicating which method was called and the reason for the error. Use the main function defined below to produce the output that follows.

Main Function:

int main(void) {

      Rectangle r;

      try {

            while (true) {

                  int l, w;

                  cout << \"Enter a length: \";

                  cin >> l;

                  cout << \"Enter a width: \";

                  cin >> w;

                  r.setLength(l);

                  r.setWidth(w);

                  cout << \"The area is: \" << r.area() << endl;

            }

      } catch (DimError de) {

            cout << \"Couldn\'t set the rectangle\'s dimensions: \" << endl

                  << de.what() << endl;

      }

      cout << \"Exiting...\" << endl;

      return 0;

}

Output:

Enter a length: 5

Enter a width: 10

The area is: 50

Enter a length: 3

Enter a width: 3

The area is: 9

Enter a length: -3

Enter a width: 5

Couldn\'t set the rectangle\'s dimensions:

setLength called with a negative length.

Exiting...

Press any key to continue . . .

Solution

Please follow the code and comments for description :

CODE :

#include <cstdlib> // required header files
#include <iostream>
#include <string>
#include <stdexcept>
#include <exception>

using namespace std;

class DimError { // class that has the exception defined
public:

DimError(const string& msg) : message(msg) { // empty constructor
}

string what() const { // get the message fromt the user
return (message);
}

private:
string message; // variable that holds the message
};

class Rectangle { // class that takes in the the dimesnions of the rectangle
int LengthData, WidthData, areaOfRect;

public:

void setLength(int length) { // method that takes the length
if (length < 0) { // check for the data
throw DimError(\"setLength called with a negative length.\"); // throw the exception
} else {
LengthData = length; // else data
}
}

void setWidth(int width) { // method that takes the width
if (width < 0) { // check for the data
throw DimError(\"setWidth called with a negative width.\"); // throw the exception
} else {
WidthData = width; // else data
}
}

double area() { // method that returns the result as area
areaOfRect = WidthData * LengthData; // code to calculate the area
return areaOfRect; // return area
}

};

int main(void) { // driver method
Rectangle r; // object for the class
try { // try catch block
while (true) { // iterate tiil teh user exits
int l, w; // local variables
cout << \"Enter a length: \"; // prompt
cin >> l; // get data
cout << \"Enter a width: \"; // prompt
cin >> w; // get data
r.setLength(l); // call the functions
r.setWidth(w);
cout << \"The area is: \" << r.area() << endl; // print data to console
}
} catch (DimError& de) { // catch the error
cout << \"Couldn\'t set the rectangle\'s dimensions: \" << endl << de.what() << endl; // print the message
}
cout << \"Exiting...\" << endl; // exit prompt
return 0;
}

OUTPUT :

Enter a length: 5
Enter a width: 10
The area is: 50
Enter a length: 3
Enter a width: 3
The area is: 9
Enter a length: -3
Enter a width: 5
Couldn\'t set the rectangle\'s dimensions:
setLength called with a negative length.
Exiting...

Hope this is helpful.