In-Class Exercise
Helper Operators
This exercise overloads a helper operator, enabling
client programs to use objects in expressions that create
new objects from the operands that don't change in value.
Given Information
The following code is a solution to the Handout on
Member Operators.
Client Module
// Member Operator
// h8.cpp
#include <iostream>
using namespace std;
#include "Employee.h"
int main() {
Employee null,
mark(3456, "Mark"),
rose(3457, "Rose", 10.70);
null.display();
cout << endl;
null += 0.50; // raise of 50 cents
null.display();
cout << endl;
mark.display();
cout << endl;
mark += 0.50; // raise of 50 cents
mark.display();
cout << endl;
rose.display();
cout << endl;
rose += 0.50; // raise of 50 cents
rose.display();
cout << endl;
}
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Employee Module
Employee.h
// Member Operators
// Employee.h
const double MIN_WAGE = 10.25;
const int MAX_NAME = 20;
class Employee {
int no;
char name[MAX_NAME + 1];
double rate;
public:
Employee();
Employee(int, const char*);
Employee(int, const char*, double);
void display() const;
Employee& operator+=(double);
};
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Employee.cpp
// Member Operators
// Employee.cpp
#include <iostream>
#include <iomanip>
#include <cstring>
#include "Employee.h"
using namespace std;
Employee::Employee() {
// safe empty state
no = 0;
name[0] = '\0';
rate = MIN_WAGE;
}
Employee::Employee(int n, const char* nm) {
Employee temp(n, nm, MIN_WAGE);
*this = temp;
}
Employee::Employee(int n, const char* nm, double r) {
if (n > 0 && nm[0] != '\0' && r >= MIN_WAGE) {
no = n;
strncpy(name, nm, MAX_NAME); // copy first MAX_NAME characters
name[MAX_NAME] = '\0'; // ensure that last byte is null
rate = r;
} else {
Employee temp;
*this = temp;
}
}
void Employee::display() const {
if (no > 0) {
cout << fixed << setprecision(2);
cout << name << " (" << no << ") $" << rate;
}
else
cout << "no data available";
}
Employee& Employee::operator+=(double r) {
if (no > 0 && r > 0.0)
rate += r;
return *this;
}
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Your Task
Upgrade the Employee
module to overload the + operator in two
ways:
- overload the
+ operator for an Employee
object as the left operand and a double as the right
operand
- overload the
+ operator for a double as
the left operand and an Employee
object as the right operand
In each case, use an independent helper definition (non-friend).
Client Module
The client program that uses the upgraded class looks something
like
// Helper Operator
// h9.cpp
#include <iostream>
using namespace std;
#include "Employee.h"
int main() {
Employee null,
mark(3456, "Mark"),
rose(3457, "Rose", 10.70);
null.display();
cout << endl;
null = null + 0.50; // raise of 50 cents
null.display();
cout << endl;
mark.display();
cout << endl;
mark = mark + 0.50; // raise of 50 cents
mark.display();
cout << endl;
rose.display();
cout << endl;
rose = 0.50 + rose; // raise of 50 cents
rose.display();
cout << endl;
}
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Employee Module
Employee.h
Add your prototype declarations after the class definition:
// Helper Operator
// Employee.h
const double MIN_WAGE = 10.25;
const int MAX_NAME = 20;
class Employee {
int no;
char name[MAX_NAME + 1];
double rate;
public:
Employee();
Employee(int, const char*);
Employee(int, const char*, double);
void display() const;
Employee& operator+=(double);
};
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Employee.cpp
Add the helper operator definitions to the implementation file:
// Helper Operator
// Employee.cpp
#include <iostream>
#include <iomanip>
#include <cstring>
#include "Employee.h"
using namespace std;
Employee::Employee() {
// safe empty state
no = 0;
name[0] = '\0';
rate = MIN_WAGE;
}
Employee::Employee(int n, const char* nm) {
Employee temp(n, nm, MIN_WAGE);
*this = temp;
}
Employee::Employee(int n, const char* nm, double r) {
if (n > 0 && nm[0] != '\0' && r >= MIN_WAGE) {
no = n;
strncpy(name, nm, MAX_NAME); // copy first MAX_NAME characters
name[MAX_NAME] = '\0'; // ensure that last byte is null
rate = r;
} else {
Employee temp;
*this = temp;
}
}
void Employee::display() const {
if (no > 0) {
cout << fixed << setprecision(2);
cout << name << " (" << no << ") $" << rate;
}
else
cout << "no data available";
}
Employee& Employee::operator+=(double r) {
if (no > 0 && r > 0.0)
rate += r;
return *this;
}
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