must be modifiable value error? - c++

Question

below is a .cpp file that i am including in another .cpp file. I am getting an error that states emp.grosPay() must be a modifiable lvalue. any ideas on fixing it?
#include <iostream>
#include <string>
#include "weeklyEmp.h"
using namespace std;
const double WEEKLY_ALLOWANCE = 39.42;
const double FICA_TAX_RATE = 0.0765;
weeklyEmp::weeklyEmp()
{
my_name = ?name?;
}
weeklyEmp::weeklyEmp(string initName,
double initHours,
double initRate,
int initExemptions,
string initFilingStatus)
{
my_name; initName;
my_hours; initHours;
my_rate; initRate;
my_exemptions; initExemptions;
my_filingStatus; initFilingStatus;
}
//--modifiers
void weeklyEmp::set_hours(double thisWeeksHours)
//post: Set the hours worked for a given week
{
my_hours = thisWeeksHours;
}
void weeklyEmp::set_rate(double thisWeeksRate)
//post: Change the employee's hourly rate of pay
{
my_rate = thisWeeksRate;
}
//--accessors
double weeklyEmp::grosPay() const
//post: Return gross pay with overtime
{if(my_hours <=40) return my_hours * my_rate;
else
return (40*my_rate) + (my_hours-40) * 1.5 * my_rate;
}
double weeklyEmp::incomeTax() const
//post: Return the federal income tax
{
double result(0.0);
double taxableIncome(grosPay() - my_exemptions * WEEKLY_ALLOWANCE);
if(my_filingStatus == "S" || my_filingStatus == "s")
{
if (taxableIncome <= 23.00)
result = 0.00;
else if(taxableIncome <= 397.00)
result = 0.15 * (taxableIncome - 23.00);
else if(taxableIncome <= 928.00)
result = 56.10 + 0.28 * (taxableIncome - 397.00);
else if(taxableIncome <= 2121.00)
result = 204.78 + 0.33 * (taxableIncome - 928.00);
else
result = 598.47 + 0.28 * (taxableIncome - 2121.00);
}
if(my_filingStatus == "M" || my_filingStatus == "m")
{
if(taxableIncome <= 65.00)
result = 0.00;
else if(taxableIncome <= 689.00)
result = 0.15 * (taxableIncome - 65.00);
else if(taxableIncome <= 1573.00)
result = 93.60 + 0.28 * (taxableIncome - 689.00);
else if(taxableIncome <= 3858.00)
result = 341.12 + 0.33 * (taxableIncome - 1573.00);
else
result = 1095.17 + 0.28 * (taxableIncome - 3858.00);
}
/* round to the nearest penny */
/* include compfun.cpp for round function */
result =(result, 2);
return result;
}
double weeklyEmp::FICATax() const
//post: Return the social security tax
{
return grosPay() * FICA_TAX_RATE;
}
string weeklyEmp::name() const
//post: Return the employee's name
{ return my_name;
}
The portion of code with the error is below and marked * **
int main()
{
string name;
double rate;
double hours;
int exemptions;
string filingStatus;
cout <<"Name: ";
cin >> name;
cout << "Hourly Rate:";
cin >> rate;
cout << "Hours Worked:";
cin >> hours;
cout << "Exemptions: ";
cin >> exemptions;
cout<< "S) ingle / M) arried: ";
cin >> filingStatus;
cout << " " << endl;
weeklyEmp emp(name, hours, rate, exemptions, filingStatus);
double net = ***emp.grosPay()*** = emp.incomeTax() - emp.FICATax();
}

Answer 1

double net = emp.grosPay() = emp.incomeTax() - emp.FICATax();
// ^^^
grosPay doesn't return a reference, so I'm assuming you didn't mean to use an = sign there. May have been a slip of the thumb.
Did you mean to use the minus operator -?:
double net = emp.grosPay() - emp.incomeTax() - emp.FICATax();
// ^^^
The error was occurring because you can't modify a const object, an object returned by a const function, or an rvalue that isn't bound to a non-const rvalue-reference.

Answer 2

double net = ***emp.grosPay()*** = emp.incomeTax() - emp.FICATax();
^^^
The second '=' should be a '-' sign; I think you're trying to subtract, not assign.