// (a) complete the body of this copy constructor // .... } // destructor ~examT
ID: 3694428 • Letter: #
Question
// (a) complete the body of this copy constructor // .... } // destructor ~examType()
{ // (b) complete the body of this destructor // .... } int getNoOfStudents() { return noOfStudents; } void setGrade(int thePosition, double newGrade) { grades[thePosition] = newGrade; } double getGrade(int thePosition) { return grades[thePosition]; } double getAverage() { double total = 0; for (int i=0; i < noOfStudents; i ++) { total +=grades[i]; } return total/noOfStudents; } }; int main() { int size; // ask number of students taking the exam cout << "Enter no of students took the midterm: "; cin >> size; examType midterm1(size); //----------------------------- // get grades from the user for (int i = 0; i< size; i ++) { double newGrade; cout << "Enter grade for student " << (i+1) << ": "; cin >> newGrade; midterm1.setGrade(i, newGrade); } // print the grades cout << endl << "Printing grades " << endl; for (int i =0; i< size; i ++) { cout << "Student " << (i+1) << ": " << midterm1.getGrade(i) << endl; } // print Average cout << "The midterm1 average is: " << midterm1.getAverage() << endl; // Declaring another examType object called midterm2 // and initialize midterm2 by using the value of midterm1 object // NOTE THAT, the line below automatically invokes the copy constructor of the class examType // for midterm2. That is, midterm1 becomes theOtherExam in the copy constructor. examType midterm2 (midterm1);
// (c) print average for midterm2 (hint: the average for midterm1 and midterm2 should be the same if you have written // the copy constructor for examType class correctly). //... system("pause"); return 0; }
Explanation / Answer
#include <iostream>
#include <string>
using namespace std;
// this class is implemented to hold the grades for an exam
class examType
{
private:
int maxNoOfStudents; // this is the max size of the dynamic list
int noOfStudents; // this is the current number of elements in the dynamic array
double *grades; // grades is a pointer the the dynamic array
public:
// constructor with parameters
examType(int maxSize)
{
noOfStudents = 0;
maxNoOfStudents = maxSize;
grades = new double[maxNoOfStudents];
}
~examType()
{
delete[] grades;
grades = NULL;
}
//syntax on 879
examType& operator=(const examType&);
// overload the assignment operator = to allow deep copy of the grades pointer!
//...
int getNoOfStudents()
{
return noOfStudents;
}
int getMaxNoOfStudents()
{
return maxNoOfStudents;
}
void append(double newGrade)
{
if (noOfStudents < maxNoOfStudents)
{
grades[noOfStudents] = newGrade;
noOfStudents++;
}
else
{
cout << "Error: This list cannot get more elements. " << endl;
}
}
double getGrade(int thePosition)
{
return grades[thePosition];
}
void print()
{
cout << "Number of Students in the Exam: " << noOfStudents << endl;
for (int i = 0; i < noOfStudents; i++)
{
cout << grades[i] << " ";
}
cout << endl;
}
};
//noOfStudents ~~ length
//maxNoOfStudents ~~ maxSize
//grades ~~ p
examType& examType::operator=(const examType& examObject){
//syntax of overloading the assignment operator is on page 879
if (this != &examObject){
this->maxNoOfStudents = examObject.maxNoOfStudents;
noOfStudents = examObject.noOfStudents;
delete[] this->grades;
grades = new double[maxNoOfStudents];
for (int i = 0; i < noOfStudents; i++)
grades[i] = examObject.grades[i];
}
return *this;
}
int main()
{
examType midterm(10);
examType copyOfMidterm(4);
// enter grades for midterm1
midterm.append(50);
midterm.append(100);
midterm.append(80);
// print results for midterm 1
midterm.print();
copyOfMidterm = midterm; // by default assignment operator = does shallow copy here.
// your job is to overload the assignment operator = in the class above, so that deep copying is done!
copyOfMidterm.print();
copyOfMidterm.append(55); // add a new grade to copyOf Midterm
// *****hint: if you overloaded the = operator correctly and did deep copying you
// should see that the copyOfMidterm object prints the additional grade!
midterm.print();
copyOfMidterm.print();
system("pause");
return 0;
}
sample output
Number of Students in the Exam: 3
50 100 80
Number of Students in the Exam: 3
50 100 80
Number of Students in the Exam: 3
50 100 80
Number of Students in the Exam: 4
50 100 80 55
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