do-while loops annual increase - c++

Question

I have been working on this assignment for over 4 hours and it is due in 2 hours and I am just getting further back now. I had it actually outputting the first year correct, but all the other years weren't. I have been working on it so much I can't even get it to work now, I am just getting errors.
A health club currently charges $250.50 a year for membership. It has announced that it will increase its membership fee by 2% each year for next 7 years.
Write a program that uses a do-while loop to display the current rate, and then the projected rates for the next 7 years. Start at year=0, meaning the current year. The following should be the display.
Hint 1: Create a double variable charges and initialize it with the first year membership. Inside the loop, update charges by adding 2% to it.
Hint 2: Use header, setprecision(2), fixed and setw() options.
#include <iostream>
#include <string>
#include <iomanip>
using namespace std;
int main()
{
const string ID = "Matthew Valdez - CS1361-D10 - Assignment 25";
double membership,
years = 1,
initialMembership = 250.50,
membershipIncrease = .02;
cout << ID << endl << endl;
cout << "Year Charges" << endl;
cout << "------------" << endl;
{
cout << setprecision(2) << fixed;
cout << left << setw(5) << "0" << initialMembership << right << setw(5) << endl;
}
do
{
cout << left << setw(5) << years++ << initialMembership *= membershipIncrease << right << setw(5) << endl;
} while (years < 8);
return 0;
}
The error I am getting is expression must have integral or unscope enum type and <<: illegal left operand has type "double"

Answer 1

You are running into problems due to operator precedence.
Since << has higher precedence than *=, the line
cout << left << setw(5) << years++ << initialMembership *= membershipIncrease << right << setw(5) << endl;
is equivalent to
(cout << left << setw(5) << years++ << initialMembership) *= (membershipIncrease << right << setw(5) << endl);
which is far from what you intended to do.
Make your code simpler by splitting that statement into two.
initialMembership *= membershipIncrease;
cout << left << setw(5) << years++ << initialMembership << right << setw(5) << endl;
This is a personal preference but you don't need to increment year in the same line. You can use:
initialMembership *= membershipIncrease;
cout << left << setw(5) << years << initialMembership << right << setw(5) << endl;
++years;